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624 Cards in this Set
- Front
- Back
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name a vitamin humans can't synthesize
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folic acid
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folic acid AKA
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vitamin B9
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sources of folic acid
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leafy green veg
shrooms asparagus liver kidney steak yeast |
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problem with obtaining folic acid from the diet (2)
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destroyed by cooking and reducing agents
unstable when stored |
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which form of folate is destroyed by cooking and unstable when stored
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folate polyglutamate
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where is folate deficiency particularly prevalent
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underdeveloped countries in the tropics
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who in developed countries is commonly folate deficient
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indigents
elderly people |
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who is particularly vulnerable to folate deficiency
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pregnant women
infants |
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tropical sprue
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general deficiency in absorption of many nutrients from the small intestine
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type of anemia in which folate deficiency is commonly involved
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megaloblastic
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effects of folate deficiency
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1. neural tube defect
2. premature atherosclerosis and thromboembolism 3. suppression of DNA synthesis 4. megaloblastic anemia 5. depression 6. schizoid psychosis 7. increased risk of colorectal cancer 8. neurological - peripheral neuropathy, myelopathy, restless legs |
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why premature atherosclerosis and thromboembolism occur with folate deficiency
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increased plasma homocysteine
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megaloblastic anemia
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results from inhibition of DNA synthesis during red blood cell production
the cell cannot progress from G2 to M phase so the cells are large "immature erythrocytes" |
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megaloblastic anemia is a type of _____ anemia
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macrocytic
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why folate deficiency increases risk of colorectal cancer
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decreased DNA methylation
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drugs that cause folate deficiency (8)
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anti-psychotics
anti-epileptic oral contraceptives smoking alcohol methotrexate NO anaesthesia methionine |
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genetic causes of folate deficiency (2)
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hyperhomocysteinemia
ulcerative colitis |
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3 constituents of THF
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pteridine
PABA L-glutamic acid + poly glutamate side chain (variable length) |
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what is composed of these 3 subunits:
pteridine PABA L-glutamic acid + poly glutamate side chain (variable length) |
THF
|
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folyl/pteroyl moiety
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pteridine + PABA
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How does PABA bind to the glutamate residues
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γ-glutamyl linkage
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Why humans can't make their own folate
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Can't make pteridine, PABA, or a γ-glutamyl linkage
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γ-glutamyl linkage
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Linking through the R group
Needs special enzyme to break |
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important atoms in the THF molecules
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N5 and N10
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story of THF absorption
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folate polyglutamate in diet
hydrolyzed in the lumen by conjugase (Dependent on Zn) Folate monoglutamate metabolized in the lumen transported to cells 5-methyl THF enters cells via ATP dependent transport methionine synthase converts 5 methyl THF to THF polyglutamate synthase converts THF to polyglutamates for storage |
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form of folate found in food
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folate polyglutamate
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enzyme that is dependent on Zn
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conjugase (Converts folate polyglutamate to folate monoglutamate)
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conjugase is dependent on ___
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Zn
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entry of 5 Methyl THF into cells is dependent on ____
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ATP
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which cells take up lots of 5 methyl THF (2)
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liver
bone marrow |
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active form of folic acid
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THF
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form of folic acid that enters peripheral cells
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5 methyl THF
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form of folic acid that is stored within the cell
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polyglutamates
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what enzyme converts polyglutamates back into THF
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gamma glutamyl hydrolase
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which part of THF is connected by gamma glutamyl linkage
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PABA to the glutamate residues
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memorize chart #1 on the remember page
|
ok
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trade name for folinic acid
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leucovorin
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3 inhibitors in the folate pathway
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phenytoin: 5,10-methylene THF reductase
5-FU: thymidylate synthase methotrexate, aminopterin: Dihydrofolate reductase |
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purine synthesis
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ribose-5-phosphate
[ribose-5-phosphate-pyrophosphokinase] PRPP [amidophosphoribosyltransferase] PPRP-NH2 9 steps inosine |
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regulation in the purine synthesis pathway
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IMP, AMP and GMP inhibit ribose-5-phosphate pyrophosphokinase
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modifications of ____ lead to AMP and GMP
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inosine
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structure of inosine
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2 rings (resembles purine) with ribose-5-phosphate attached
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how is purine synthesis associated with folate
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2 of the 1C units in purines are from tetrahydrofolate
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cofactor for methionine synthase
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vitamin B12
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What happens to 5 methyl THF's 1C
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Donated to homocysteine to make methionine
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what is the de novo path
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serine --> glycine
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how does 5-FU work
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dUMP analogue
Inactivates thymidylate synthase permanently (=suicide inhibition) |
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5-FU inhibits thymidylate synthase permanently - why are the effects not permanent (ie. Why do we need to dose repeatedly)
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The cell makes new thymidylate synthase
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suicide inhibition
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irreversible inhibition that occurs at the active site
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people who commonly get B12 deficiency
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vegans
gastrectomy patients Crohn's disease elderly |
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Leucovorin AKA
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folinic acid
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type of inhibition of 5-FU vs. aminopterin and methotrexate
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5-FU: suicide
aminopterin & methotrexate: competitive depends on inhibitor conc |
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folinic acid =
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5 formyl THF
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role of folinic acid in 5-FU therapy
|
also inhibits thymidylate synthase
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role of folinic acid in methotrexate therapy
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provides a source of 1C units to rescue normal cells from the chemotherapeutic effects
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which has more Cs: glycine/serine
|
serine
|
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methotrexate is an analogue of
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folic acid
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side effects of methotrexate therapy
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myelosuppression
mucositis |
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name of the cycle involving methionine and homocysteine
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Remethylation cycle
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name 2 B6 dependent enzymes
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cystathione beta synthase
gamma cystathionase |
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methionine synthase cofactor
|
B12
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unusual use of ATP
|
not used for its high energy bond but for its adenosine to make S-adenosyl-methionine
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things that can be methylated by SAM and methyl-transferase
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DNA
drugs phospholipids proteins |
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role of DNA methylation
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regulates expression
|
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inhibitor of methionine synthase
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NO anaesthetic
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inactivators of methionine adenosyltransferase
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chronic alcoholism
hypoxia viral liver cirrhosis septic shock |
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what does NO anaesthetic inhibit
|
methionine synthase
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chronic alcoholism
hypoxia viral liver cirrhosis septic shock these are all associated with |
inactivation of methionine adenosyltransferase
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downstream effects of inactivating methionine adenosyltransferase
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methylation deficiency
cysteine deficiency -> GSH deficiency |
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cofactor for cystathione beta synthase and gamma cystathionase
|
B6
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B6 AKA
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pyridoxine
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B9 AKA
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folate
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B12 AKA
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cobalamin
|
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folate trap
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if there is insufficient vitamin B12 in the diet, 5-methyl THF cannot be converted into THF and homocysteine cannot be converted into methionine
Result is hyperhomocysteinemia folate (B9) deficiency can also induce hyperhomocysteinemia - because you need to 1C donator to convert homocysteine to methionine |
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causes of the folate trap (hyperhomocysteinemia)
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organ damage
genetic vitamin deficiency |
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Result of hyperhomocysteinemia
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Premature atherosclerosis and/or thrombosis
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3 vitamin deficiencies that can lead to elevated homocysteine
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B6
B9 B12 |
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how B6 deficiency leads to hyperhomocysteinemia
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required for cystathione beta synthase activity
this converts homocysteine into cystathione If B6 is not available, this reaction does not occur, and homocysteine builds up |
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how B9 deficiency leads to hyperhomocysteinemia
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source of 1C units to transfer onto homocysteine to form methionine
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how B12 deficiency leads to hyperhomocysteinemia
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methionine synthase requires vitamin B12
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CBS
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cystathione beta synthase
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MTHFR
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5, 10 methylene THF reductase
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genetic enzyme deficiencies that result in hyperhomocysteinemia
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MTHFR
methionine synthase cystathione beta synthase |
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what type of disorder is CBS deficiency
|
autosomal recssive
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name an autosomal recessive disorder
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CBS deficiency
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organ systems affected by CBS deficiency
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ocular - lens dislocation
CNS skeletal |
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do you need more folic acid to prevent fetal defects or to prevent vascular disease
|
vascular disease
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how hypercysteinemia causes atherosclerosis
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1. forms homocysteine-thiolactone
2. this acts as an LDL-R 3. homocysteine-thiolactone-LDL-R form aggregates 4. the aggregates recruit foam cells 5. foam cells recruit ROS lipid peroxidation LDL oxidation proliferation of vascular smooth muscle cells |
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Down's syndrome inheritance
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trisomy 21
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Down's syndrome and CBS
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increased CBS activity
low homocysteine elevated cystathione hypermethylation in DNA |
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structure of vit B12
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analogous to heme
cobalt centre with 6 coordinating bonds corrin ring |
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where is B12 produced
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bacteria
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how do lacto-ovo vegetarians get B12
|
bacteria on plants
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2 enzymes that depend on B12
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methylmalonyl CoA mutase
methionine synthase |
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when you might need more B12
|
When you need 1C metabolism
Chemotherapy Pregnancy maintenance of hematopoietic and nervous systems |
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Oxidation state of Co in Vit B12
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Co (III)
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List 4 vit B12 ligands - they are attached to the cobalt
|
CN
OH Ado CH3 |
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CN ligand of vit B12
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cyanocobalamin
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OH ligand of vit B12
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hydroxocobalamin
|
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Ado ligand of vit B12
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5' deoxyadenosylcobalamin
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CH3
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methylcobalamin
|
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use of CN (vit B12)
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supplement
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use of OH (vit B12)
|
cyanide and hydrogen sulfide antidote
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use of Ado (vit B12)
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amino acid metabolism
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use of CH3 (vit B12)
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methylation
homocysteine -> methionine |
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Story of vitamin B12 uptake and distribution
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Stomach:
1. Protein digestion frees B12 2. B12 binds to cobalophilin Duodenum: 1. cobalophilin/B12 complex is hydrolyzed, releasing B12 2. B12 binds to intrinsic factor Distal ileum B12/IF complex absorbed |
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Source of cobalophilin
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saliva
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where is intrinsic factor made
|
parietal cells of the stomach
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what cannot be absorbed
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B12 or IF alone
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what is B12 bound to in the blood
|
transcobalamin II
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symptoms of B12 deficiency
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1. increased plasma methylmalonyl CoA and homocysteine
2. pale, shiny tongue -> red, sore, glossitis (inflam of the tongue) |
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what is B12 bound to in cells
|
transcobalamin I and III
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situations in which B12 deficiency is caused by impaired binding to intrinsic factor (2)
|
pernicious anemia
Crohn's |
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cause of pernicious anemia (2)
|
genetic
autoimmune |
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pernicious anemia
|
lack of intrinsic factor
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Production of succinyl coA
|
Methionine/valine/isoleucine are made into:
proprionyl CoA [proprionyl CoA carboxylase] Methylmalonyl coA [methylmalonyl CoA mutase - B12 dependent] succinyl CoA TCA cycle |
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when B12 deficiency occurs - what is the implication based on the succinyl CoA cycle
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methylmalonyl CoA will not produce succinyl CoA for the TCA cycle
result is reduced TCA cycle activity and severe growth retardation |
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role of B12 in methionine synthase
|
the methyl transferring reaction occurs at the cobalt centre
Co gets converted to the +1 state during the homocysteine -> methionine reaction gets oxidized back to the +3 state after |
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% methionine requirement provided by diet
|
50
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why tongue symptoms of B12 deficiency
|
can't replicate DNA efficiently
tongue normally invaginated, when it can't replicate quickly, it doesnt have enough cells for the invaginations |
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Causes of B12 deficiency
(4) |
Genetic mutation
NO anaesthetic Oral contraceptives Hormone replacement therapy |
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Consequences of B12 deficiency
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Diseases of bone marrow, intestinal tract, CNS
increased methyl malonyl CoA causes growth retardation • increased plasma homocysteine premature atherosclerosis, thromboembolism • depression and dementia in geriatrics • cognitive impairment in the elderly, peripheral neuropathy • multiple sclerosis (demyelination disorder) • morbidity in transplant patients |
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Pernicious anemia - 2 causes
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B12 or intrinsic factor deficiency
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2 problems associated with pernicious anemia
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1. Reduction in B12 blocks metabolism of folic acid => secondary folate deficiency
2. Impaired erythropoiesis => premature release of immature erythrocyte precursors (megaloblastic anemia) |
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2 things that help reduce malaria risk
|
Sickle cell
G6PD deficiency |
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Component of fava beans
|
Vicine
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How to get rid of vicine
|
Cook the beans
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What happens to vicine in stomach
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Low pH breaks it into glucose and divicine
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What happens to divicine in the body
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Undergoes cycling between the reduced and oxidized forms
When it is oxidized it donates an electron to O2 making superoxide anion Result is increased need for NADPH and GSH |
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ultimate downstream effect of ROS in the RBC
|
hemolytic anemia
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favism
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Hemolytic response to consumption of fava beans
all individuals with favism have G6PD deficiency but not all individuals with G6PD deficiency show favism when exposed to the beans |
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why oxygen is important
|
terminal electron acceptor in oxidative phsophorylation
This allows production of way more ATP than just glycolysis |
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free proteins in blood (6)
|
albumin
alpha 1 acid glycoprotein globulin ferritin hormones enzymes |
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example of globulin in blood
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Ig
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partial pressure of O2 in lungs
|
100mmHg
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partial pressure of O2 in tissues
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5-30mmHg
different at arterial and venous ends |
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shape and structure of RBC (3)
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round
biconcave flexible |
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what happens in uncontrolled diabetes
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high blood sugar =>
RBC coated with glucose => RBC clumping => capillary damage => impaired circulation => opportunistic pathogen => amputation |
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haematocrit
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volume % of RBCs in blood
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usual values for haematocrit
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35-50%
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is haematocrit lower for females or males
|
females
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system that breaks down RBCs
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reticuloendothelial
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where are RBCs broken down (3)
reticuloendothelial system |
spleen
liver bone marrow |
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jaundice in newborns - why
|
1. newborns have high turnover of RBCs
2. so they make more bilirubin than adults 3. their liver is still developing, so they may be unable to remove bilirubin from the blood |
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stages of RBC development
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BONE MARROW
hemocytoblast proerythroblast early erythroblast (ribosome synthesis occurs) late erythroblast (Hb synthesis occurs) normoblast (Hb synthesis continues; cellular organelles and nucleus ejected, cells leave bone marrow and go to spleen) reticulocyte (ribosomes ejected, leaves bone marrow, becomes erythrocyte) |
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what RBCs do not have that most cells have
|
nucleus
membrane bound organelles ribosomes |
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why are RBCs susceptible to oxidative effects
|
they cannot repair themselves as they have no DNA or protein-making machinery
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at which point does the stem cell commit to becoming an RBC
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proerythroblast
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why RBCs that are not fully developed may be found in the blood
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body being pushed too hard to make RBCs
|
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What might cause RBC production to be hurried (2)
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Bleeding
Drugs |
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Where are RBCs produced in fetuses
|
liver
|
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fetus RBC production
|
before 4 months: liver
4-7 months: liver and bone marrow after 7 months: bone marrow |
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because RBCs do not have nuclei or ribosomes, they cannot produce RNA or proteins. They lack another organelle that prevents them from performing another normal cellular function
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no mitochondria so no aerobic respiration
|
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how does the RBC meet its energy needs
|
glycolysis
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structure of myoglobin
|
heme + lots of alpha helices
|
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how many bonds does the iron atom in heme form
|
6
|
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What bonds does the heme iron form
|
4 bonds to N in heme protein (within plane) 1 His in the heme protein
1 O2 bond |
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what kind of subunits form the heme molecule
|
pyrrole
|
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How is hemoglobin reused
|
Transferritin transports the iron
The globin chain itself is broken down and the aas can be reused heme is broken down and used for other things (ex. bilirubin) |
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why myoglobin doesn't display cooperativity
|
only 1 heme per protein
one oxygen per protein |
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shape of myoglobin saturation % vs, partial pressure of O2
|
hyperbolic
|
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what is a P50
|
the pressure at which Hb (or Mb) saturation is 50%
|
|
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PO2 in tissues that need oxygen
|
5-20mmHg
|
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does myoglobin have a high or low p50
|
low
|
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what does a low P50 mean
|
holds oxygen tighter
don't need much O2 to reach 50% saturation |
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Tetrameric structure of Hb imparts it with 2 important properties
|
1. Allosterism: binding of O2 at one site affects O2 binding at distal sites
2. Positive cooperativity: affinity for 4th O2 is much greater than for the first |
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shape of Hb sat curve (% saturation vs. PO2)
|
sigmoidal
|
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p50 of Hb
|
26
|
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Hill plot math
|
Y = fraction of binding sites occupied
Y / (1-Y) = pO2/pO2(50) Log [ (Y / (1-Y) ] = log pO2 - log pO2(50) Hill plot: Y axis: log [ log (Y / (1-Y) ] x axis: log pO2 slope of 1 means no cooperativity |
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2 conformational (stable) states of Hb
|
deoxy (T - tense)
fully oxygenated (R - relaxed) |
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Perutz mechanism
|
when bound to O2: Fe is perfectly in the plane of the porphyrrin ring
when not bound to O2: Fe is slightly elevated from the plane Fe moving wrt to plane moves the amino acid chain (via the Fe-His bond) Aspartic acid has negative formal charge. His has partial + charge In deoxy state these are close together and form a salt bridge The first oxygen binding breaks all salt bridges such as these, and that is why it takes the most E to bind |
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in which state of Hb is the binding pocket smaller
|
R (oxygenated)
|
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oxygenated = R or T
|
R
|
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deoxygenated = R or T
|
T
|
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Bohr effect (series of events)
|
metabolism produces CO2 and H+ ==>
decreased pH in RBCs ==> protonation of some aas in Hb ==> T state stabilized ==> affinity of Hb for O2 decreases |
|
|
Bohr effect on the saturation vs. pO2 curve
|
visualize by drawing horizontal and vertical lines on the graph
right - for any given saturation, there is a higher partial pressure - you need more oxygen to reach that level of saturation down - for any given partial pressure there is a lower saturation |
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Rxn that lowers pH when CO2 is produced
|
2 CO2 + 2 H2O ---(carbonic anhydrase) ---> 2 H2CO3 ---> 2 H+ + 2 HCO3-
|
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H2CO3
|
carbonic acid
|
|
|
HCO3-
|
bicarbonate ion
|
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|
typical blood pH
|
7.4
|
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ways that CO2 is excreted (3)
|
1. dissolved gas
2. bound to Hb 3. combined with water in carbonic acid |
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which of the 3 ways is most CO2 excreted
|
combined with water in carbonic acid
|
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where is carbonic anhydrase found
|
RBCs
|
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chains that comprise HbA (adult)
|
2 alpha
2 beta |
|
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chains that comprise HbF
|
2 alpha
2 gamma |
|
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what is the role of non alpha/beta/gamma Hb chains
|
zeta and epsilon are present very early in gestation
|
|
|
main difference between HbF and HbA
|
HbF holds O2 more tightly
ensures net transfer of O2 to the fetus |
|
|
people who have a problem with Hb synthesis can promote ____ chain production
|
delta
|
|
|
isohydric transport
|
there is lots of CO2 in actively respiring tissue
CO2 diffuses into RBC 2 CO2 + 2 H2O ---(carbonic anhydrase) ---> 2 H2CO3 ---> 2 H+ + 2 HCO3- bicarbonate ion builds up, so it needs to leave the cell to maintain electric neutrality, it is exchanged with Cl- |
|
|
H+ ions decrease the affinity of Hb for O2 - what is this effect called
|
Bohr effect
|
|
|
when not bound to O2, Fe is not within the plane of the ring
this pulls the amino acid chain in such a way that Asp and His are close to each other the first O2 binding has to break this (and all) salt bridges) This is explanation of why the first O2 binding takes the most energy is called |
Perutz mechanism
|
|
|
name of this process
there is lots of CO2 in actively respiring tissue CO2 diffuses into RBC 2 CO2 + 2 H2O ---(carbonic anhydrase) ---> 2 H2CO3 ---> 2 H+ + 2 HCO3- bicarbonate ion builds up, so it needs to leave the cell to maintain electric neutrality, it is exchanged with Cl- |
isohydric transport
|
|
|
effect of isohydric transport
|
Cl- content of RBCs is much higher than arterial RBCS
|
|
|
does the Cl- HCO3 exchange require E
|
no because they are both going down their conc gradients
|
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what happens to O2 in tissues
|
Oxidative phosphorylation
Binds to myoglobin (saturated at 20mmHg) |
|
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myoglobin is saturated at ___mmHg
|
20
|
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how does protonated Hb return to regular state
|
1st O2 molecule binding donates the E to drive off the protons
|
|
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name of side reaction from glycolysis that generates BPG
|
Raport-Luenberg pathway
|
|
|
what does BPG stand for
|
2,3-bisphosphoglycerate
|
|
|
BPG AKA
|
2,3-DPG
|
|
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pathway that BPG is involved in
|
page 3
|
|
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effect of BPG
|
decreases O2 affinity of Hb by stabilizing the T state
|
|
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how does BPG stabilize the T state
|
ionic cross linking of beta chains
(salt bridges) |
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What happens when O2 affinity of Hb is decreased
|
Enhanced O2 release
|
|
|
BPG in fetal Hb vs. adult Hb
|
HbF does not bind 2,3-bisphosphoglycerate as efficiently as HbA
So HbF retains higher O2 affinity |
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Implication of BPG for pharmacists
|
Certain drugs may cause defects in glycolysis. This will alter oxygen transfer kinetics and thus, tissue oxygenation levels
|
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where does BPG come from
|
byproduct of glycolysis
|
|
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Why the BPG side rxn is not normally used instead of the main pathway
|
Replaces an ATP producing step
Does not produce any ATP |
|
|
What parameter of high altitude makes it conducive to training the CV system
|
Low partial pressure of O2
|
|
|
2 adaptations to high altitude training
|
1. short term (few days): increased BPG production
2. long term (few weeks): increased RBC production |
|
|
Quantitative info regarding BPG and high altitude training
|
BPG levels double after 2 days
|
|
|
structure of BPG
|
very small (3C)
5 negative charges |
|
|
How does BPG bind to hemoglobin
|
Binds tightly to deoxyHb, weakly to oxyHb
Binds to formal or partially delocalized positive charges on His /Lys residues (formal = Lys) (partial = His) creates a B-B linkage (linkage between the two β chains of Hb) The two β chains are farther apart in oxyHb It fits in the hole of the Hb |
|
|
Binding stoichiometry of BPG with Hb
|
4 chains, 4 O2 molecules
1 Hb tetramer, 1 BPG |
|
|
Implication of the stoichiometry of BPG
|
Don’t have to interrupt glycolysis as much as you would if you needed 4 BPG
|
|
|
How does P50 of Hb change in high altitude
|
Increase (need higher Partial pressure to oxygenate 50% of hemoglobin -> less likely to be oxygenated)
|
|
|
List of P50s from highest to lowest
(ex. whole blood, Hb + BPG...) |
whole blood
Hb + BPG + CO2 Hb + BPG Hb + CO2 stripped Hb |
|
|
Primary fuel when we have adequate dietary intake
(2) |
Carbs and fats
|
|
|
Primary fuel in starvation conditions (24 hours) (2)
|
Blood glucose
Glycogen |
|
|
common monosaccharides and how many Cs they have
|
glucose (6)
galactose (6) fructose (6) |
|
|
common disaccharides and their constituent monosaccharides
|
sucrose (g+f)
maltose (g+g) lactose (g+ga) |
|
|
what are proteins used for in the fed state (adequate dietary intake)
|
cellular protein and nucleotide metabolism
|
|
|
3 things that happen in starvation conditions
|
1. Blood glucose and glycogen used as primary fuel
2. glycerol from fat and amino acids from protein begin to be converted to glucose through gluconeogenesis 3. Glucose remains dominant fuel supply for brain, RBCs, bone marrow, WBCs, renal medulla |
|
|
Where does gluconeogenesis occur
|
liver
|
|
|
In conditions of starvation, which organs continue to use glucose provided by gluconeogenesis
|
Brain
RBCs Bone marrow WBCs Adrenal medulla |
|
|
What happens in prolonged starvation (weeks)
|
Ketone body formation begins brain begins to use ketone bodies
|
|
|
Maximum starvation time
|
100 days
|
|
|
Glycolysis AKA
|
Embden-Meyerhof (Parnas) pathway
|
|
|
glycolysis claim to fame
|
Most universal metabolic pathway in living organisms
|
|
|
Etymology of glycolysis
|
Glycos = sweet
Lysis = break |
|
|
2 main uses of glycolysis
|
Primary form of anaerobic ATP production in higher organisms
Dominant form of energy production in RBCs |
|
|
Products of glycolysis per mole of glucose
|
2 ATP
2 NADH 2 pyruvate |
|
|
Why is glycolysis not used as the main source of ATP production in the majority of mammalian cells
|
Relatively inefficient
|
|
|
Efficiency of anaerobic metabolism (in terms of % of aerobic)
|
7
|
|
|
2 unique roles of glycolysis in erythrocytes
|
1. Supplies ATP for ion pumps
2. Supplies NADH for methemoglobin reductase |
|
|
Function performed by a majority of ATP In erythrocytes
|
1. Na+/K+ transport
2. Ca++/ATPase 3. Sustain glycolysis |
|
|
Size change in RBC when ATP decreases
|
increase
|
|
|
why
|
ATP is required for the Ca pump
Ca pumped out |
|
|
Ion concentrations inside and outside from 3rd year phys
|
High outside: Na, Cl, Ca
High inside: K |
|
|
reaction of methemoglobin reductase
|
page 4 (back of page 3) in notebook
|
|
|
why the methemoglobin reductase reaction is important
|
lots of iron and lots of O2 can lead to a dangerous situation
sometimes the +2 iron oxidizes to the +3 state methemoglobin isn't as efficient wrt oxygen transport |
|
|
ferrous iron
|
+2
|
|
|
ferric iron
|
+3
|
|
|
in which direction do electrons move when oxidation number increases (+2 to +3)
|
loss of electrons = oxidation
|
|
|
reduction = gain of (2)
|
electrons
H atoms |
|
|
how many Na/K pumps per cell
|
300
|
|
|
change in RBC size when there is less Na leaking in than K leaking out
|
shrink
|
|
|
Change in RBC size when there is more Na leaking in than K leaking out
|
swell
|
|
|
inhibitor of Na/K pump
|
digitalis
auabain |
|
|
Purpose of Na/K pump inhibitors
|
Enhance muscle contractility in conditions of angina
|
|
|
Ratio of the Na/K pump
|
3 Na out 2 K in
|
|
|
Why ATP needed for Na/K pump
|
Goes against conc gradients
|
|
|
What happens when Ca leaks into the cell
|
Drugs can initiate many of the steps described below
1. Reduced Ca/ATPase activity OR reduced ATP OR membrane damage 2. Increased Ca 3. Membrane damage 4. Cell changes shape and rigidity (biconcave disc ---> echinocyte) a. Also caused by improper osmolality - cell shrinks (?) 5. Dehydrated, crenated cell 6. Not deformable 7. Trapped by the spleen 8. Engulfed by macrophages |
|
|
Progressive rise in intracellular Ca is closely tied to _____
|
RBC aging
|
|
|
What happens to aged RBCs
|
Removed by reticulo-endothelial system in spleen (macrophages)
|
|
|
Which of the ions has different concs inside cells depending on whether blood is oxygenated or not
|
Cl
|
|
|
Description of echinocyte shape
|
spiculated sphere
|
|
|
How calmodulin helps
|
Binds Ca activates Ca pump
|
|
|
Side reaction of glycolysis that is key to supplying NADPH
|
Pentose monophosphate shunt
|
|
|
pentose monophosphate shunt
|
see page 5 of notebook
|
|
|
What does pentose monophosphate remove
|
Cellular reactants such as H2O2
|
|
|
Overall role of NADPH
|
Fights free radicals
|
|
|
How does NADPH fight free radicals
|
By supporting the action of:
Glutathione (GSH) GSH reductase GSH peroxidase Catalase |
|
|
Active catalase tightly binds how many NADPH molecules
|
4
|
|
|
NADPH production is dependent on a specific enzyme
|
G6PD
|
|
|
As such, NADPH production is impaired in individuals with deficiencies in
|
g6pd
|
|
|
Inhibitors of glycolysis
(2) |
Fluoride
arsenate |
|
|
What happens in the presence of arsenate
|
ATP normally formed in the conversion of 1,3-bisPG into 3-PG is lost (no net ATP production)
|
|
|
2 reasons oxidative stress is of particular concern in the RBC
|
can't make proteins to repair
lots of Fe and O2 in the same place |
|
|
How many mole equivalents of NADPH are produced per turn of the cycle (pentose monophosphate shunt)
|
2
|
|
|
which is the reduced form: GSH or GSSG
|
GSSG is oxidized
you want it to be reduced so it has electrons to donate |
|
|
which micronutrient is required for GSH peroxidase activity
|
Selenium
|
|
|
stoichiometry of the pentose monophosphate shunt
|
reactant: 3R5P
product: 2F6P + 1 G3P |
|
|
practice the pentose monophosphate shunt (zoom in rxn)
|
page 6
|
|
|
what does transketolase do
|
moves 2C piece from one molecule to another
|
|
|
what does transaldolase do
|
moves 3C piece from one molecule to another
|
|
|
What is it called when CO binds Fe2+ Hb
|
complexing
|
|
|
presentation of CO poisoning victims
|
Show signs of cyanosis = low in oxygen
But normally cyanosis makes your skin blue or purple Lips and inside of mouth = Bright red |
|
|
Avidity of heme group for CO compared to that of oxygen
|
25 000 x greater
|
|
|
Avidity of hemoglobin for CO compared to that of oxygen
|
200x greater
|
|
|
4 types of Hb (3 of them have colours)
|
deoxyHb: Fe2+ (purple)
oxyHb: Fe2+O2 (bright red) metHb: Fe3+ (brown) cyanHb: antidote for cyanide poisoning |
|
|
ferrous iron
|
+2
|
|
|
ferric iron
|
+3
|
|
|
Relationship of metHb with O2
|
In a single hemoglobin molecule there are 4 heme moieties
If one of these is ferric iron, the O2 does not bind well to this iron centre, but it binds way more strongly than normal to all the other ferrous centres in the molecule. |
|
|
Situation where metHbemia is desirable
|
cyanide poisoning
|
|
|
how does cyanide poison you
|
inhibits cytochrome c oxidase in the electron transport chain, inhibiting ATP production
|
|
|
treating cyanide poisoning and how it works
|
CN- ion binds well to ferric iron centre
it can bind to Hb instead of cyt-c amyl and Na nitrite converts Fe2+ to Fe3+ |
|
|
drugs that induce methemoglobinemia (6)
|
aniline drugs - dapsone
quinones fava beans anaesthetics chlorates sulfonamides |
|
|
Who might be more sensitive to methemoglobinemia
|
children
|
|
|
Give an example of a genetic defect that causes someone to not be able to deal with oxidative stress very well
|
G6PD
|
|
|
How can the body return methemoglobin to oxyhemoglobin
|
Methemoglobin reductase (cytochrome B5)
|
|
|
"cofactor" for methemoglobin reductase
|
NADPH gets oxidized as methemoglobin gets reduced so the electrons go from NADPH to methemoglobin
|
|
|
2 ways to detoxify H2O2
|
Catalase
glutathione peroxidase |
|
|
methylene blue pathway
|
methylene blue administered
NADPH converts it to leucomethylene blue leucomethylene blue converts methemoglobin to oxyghemoglobin |
|
|
Methylene blue is not an appropriate treatment for which patients and why
|
Low G6PD activity
They can't make enough NADPH to convert the methylene blue to the active leucomethylene blue |
|
|
Why can’t you just give leucomethylene blue
|
Not safe to give directly
|
|
|
Superoxide radical is detoxed by SOD, and H2O2 is detoxified by catalase and GSH, but there aren't really systems in our body to detoxify ______
|
Hydroxyl radicals: OH.
|
|
|
why hydroxyl radicals don't get detoxified
|
It is so super reactive that it reacts too quickly to be detoxified - generated locally - reacts right where it is
|
|
|
how the body combats hydroxyl radicals
|
keeps the precursors at a low level
|
|
|
2 things that get damaged by hydroxyl radical
|
membrane lipids
proteins |
|
|
When excessive free radicals are generated the most downstream result of this =
|
hemolytic anemia
|
|
|
type of activity fast vs. slow twitch
|
fast: rapid contractions of brief duration
slow: sustained activity |
|
|
fast/slow twitch - where do they get their energy
|
fast: anaerobic glycolysis
slow: oxidative metabolism |
|
|
which fibre type can contract faster than oxygen can be delivered
|
fast
|
|
|
fast twitch fibres fatigue until
|
lactic acid that they produce gets reoxidized
|
|
|
which fibre type has more mitochondria
|
slow
|
|
|
which fibre type has more myoglobin
|
slow
|
|
|
which fibre type is white
|
fast
|
|
|
which fibre type has more blood vessels
|
slow
|
|
|
Cause of malignant hyperthermia
|
mutated ryanodine receptor
lets Ca into sarcolemma in response to anaesthetic |
|
|
result of malignant hyperthermia
|
excessive production of heat and acid
death from acidosis |
|
|
malignant hyperthermia is a decoupling - what does this mean
|
No longer need AP for Ca release to occur
|
|
|
How to reverse malignant hyperthermia
|
Within the first several minutes:
cool the patient Give dantrolene |
|
|
Another anaesthetic risk
|
Spontaneous abortion
|
|
|
who often gets spontaneous abortion in response to anaesthetic
|
Common in: surgery on pregnant women OR nurses
|
|
|
page 7 reactions
|
ok
|
|
|
role of NO
|
NT and vasodilator
|
|
|
ONOO AKA
|
peroxynitrite
|
|
|
role of ONOO (Peroxxynitrite)
|
inflammation and atherosclerosis
|
|
|
relative half life of the molecules involved in the free radical rxn series
|
H2O2 = longest
superoxide anion and hydroxyl radical = shortest |
|
|
3 amino acids that comprise glutathione
|
Glutamate
cysteine Glycine |
|
|
2 cells that GSH is particularly important for
|
Erythrocytes
Hepatocytes |
|
|
General role of GSH (5, one has abc)
|
Cofactor for many enzymes
Scavenges free radicals Maintains the cysteine thiols of proteins in their reduced form Reservoir of cysteine for protein synthesis Modulates 3 processes: DNA synthesis Immune processes MT processes |
|
|
Where in the cell is GSH found
|
85-90% cytosol
10-15% mitochondria |
|
|
Where in the (non RBC) cell are ROS found
|
Mitochondria - this is where O2 is being used
|
|
|
Particular drug that is detoxified by GSH
|
acetaminophen
|
|
|
Where does GSH not perform its function as a reservoir of cysteine for protein synthesis
|
Erythrocytes
|
|
|
What is unusual about the structure of GSH
|
Not connected by amide bond
But a γ-glutamyl linkage = linkage through the side chain |
|
|
What is important about the gamma glutamyl linkage = linkage through side chain
|
needs special enzymes for synthesis and breakdown
this makes it hard to break down GSH |
|
|
enzyme that cleaves GSH (because regular enzymes can't be used
|
γ-glutamyl transpeptidase (GTTP)
|
|
|
Structure of oxidized GSH
|
cysteine groups are linked by a disulfide group
|
|
|
pathway page 8
|
ok
|
|
|
in the drug-GSH reaction, which is the electrophile
|
drug
|
|
|
How the glutathione synthesis pathway is exploited in chemotherapy
|
Buthionine sulfoximine inhibits γ-glutamyl-cysteine synthetase, preventing glutathione production, thus reducing a cancer cell's defense against free radicals
|
|
|
Where are the enzymes used in GSH catabolism found
|
outside or on the surface of the cell
|
|
|
Enzymes found outside or on the surface of a cell
|
ectoenzyme
|
|
|
where is the gamma glutamyl linkage in GSH
|
between glutamate and cysteine
|
|
|
3 pathways of metabolism for acetaminophen
|
1. 60% - Sulfate conjugation mediated by sulfotransferase. Sulfate added to the OH group
2. 40% - glucuronide conjugation by glucuronosyl transferase. 3. Overflow - P450 CYP2E1 creates a toxic intermediate |
|
|
sulfate donor cosubstrate for sulfotransferase
|
PAPS
|
|
|
glucuronide donor cosubstrate for glucuronosyl transferase
|
UDPGA
|
|
|
Where are sulfate or glucuronide groups added to acetaminophen
|
OH group
|
|
|
What happens to sulfated and glucuronidated metabolites of acetaminophen
|
urinary excretion
|
|
|
What are the fates of the toxic intermediate produced from acetaminophen by 2E1
|
1. 1,4-Michael addition of GSH
2. Liver necrosis When the GSH conjugation is saturated, liver necrosis occurs |
|
|
What has happened to acetaminophen to form the toxic metabolite
|
Electronic transition - it is charged
|
|
|
There are 3 possible detoxed metabolites of acetaminophen - what are their benefits
|
All are more water soluble
Sulfate and glucuronide conjugation = electronic transitions inhibited |
|
|
What happens to the toxic intermediate when all possible detoxes are overwhelmed
|
It binds to SH moieties on proteins
Damages the proteins Occurs in the liver |
|
|
how does the toxic metabolite of acetaminophen mediate its damage (on a molecular level)
|
binds to SH moieties on proteins
|
|
|
Where are the acetaminophen reactions occurring
|
liver
|
|
|
Symptoms of liver necrosis - when do they occur
(with acetaminophen poisoning) |
Mild until 24 hrs post ingestion
|
|
|
Problem with delayed presentation of acetaminophen induced liver damage
|
liver too damaged at time of detection
|
|
|
What are the symptoms of acetaminophen induced liver damage
|
nausea
vomiting elevated AST |
|
|
what happens within 5 days of acetaminophen toxicity
|
death or resolution
|
|
|
Toxic dose of acetaminophen in children
|
140mg
|
|
|
Toxic dose of acetaminophen in adults
|
10g
|
|
|
Role of NAC (N-acetyl cysteine) in acetaminophen toxicity
|
Is water soluble
Relatively benign Cysteine itself is not tolerated It is a reductant to the toxic intermediate. |
|
|
How is G6PD deficiency inherited
|
X linked
|
|
|
characteristics of female heterozygote for G6PD deficiency
|
2 populations of RBCs - wild type and deficient
|
|
|
Which type of G6PD deficiency has numerous variations
|
B
|
|
|
Populations in which it is very common to be G6PD deficient
(4) |
Kurdish Jews
Sardinia Saudi US blacks |
|
|
types of G6PD deficiency
|
Type 1: <2%
Type 2: <10% Type 3: 10-50% Type 4: normal |
|
|
Which type of G6PD deficiency is common in black people
|
3
|
|
|
Which type of G6PD deficiency is common in Mediterranean people
|
1
|
|
|
Downstream effects of G6PD deficiency
|
N126D
V68M |
|
|
N126D mutation
|
Asparagine 126 -> aspartate
85% normal activity This mutation alone does not affect activity |
|
|
V68M mutation
|
Valine 68 -> methionine
increases rigidity affects lysine 205 - active site that binds G6P |
|
|
G6PD A
|
N126D mutation only
85% normal activity |
|
|
G6PD A-
|
both mutations
12% activity |
|
|
G6PD B
|
normal
100% activity |
|
|
Where is malaria a risk
(5) |
South and central america
Africa Middle East India Asia |
|
|
Malaria etymology
|
mala = bad
aria = air |
|
|
parasite that causes the most serious and prevalent malaria in humans
|
Plasmodium falciparum
|
|
|
who is malaria resistant
|
Heterozygote for G6PD deficiency
|
|
|
Type of parasite that plasmodium falciparum is
|
protozoan
|
|
|
role of mosquitoes in malaria
|
vector for plasmodium falciparum
|
|
|
life cycle of Plasmodium
|
Sporozoite infects liver They grow and progress through parts of their life cycle
Hepatocyte bursts Merozoite infects RBCs RBC bursts May infect another vector that bites the host |
|
|
life cycle stage of plasmodium that infects hepatocytes
|
sporozoite
|
|
|
life cycle stage of plasmodium that infects RBC
|
merozoite
|
|
|
organelle of parasite that digests Hb
|
specialized food vacuole
|
|
|
How much of an RBC's hemoglobin can be consumed
|
60-80%
|
|
|
Hemozoin
|
Disposal product from the digestion of hemoglobin by the food vacuole
|
|
|
Normal RBC vs. infected RBC
(Plasmodium) wrt glucose utilization and lactate formation |
normal: low
infected: high |
|
|
why infected cell has high glucose utilization
|
to make ATP for DNA/RNA/protein synthesis
|
|
|
How the parasite consumes hemoglobin
|
Endocytosis of Hb
Hb ----[proteases] ---> heme + amino acids heme ---> hemozoin + iron Iron is excreted from the food vacuole and is toxic |
|
|
How G6PD deficiency combats malaria
|
less NADPH produced
lower GSH:GSSG ratio (=more oxidized) less GSH to drive GSH peroxidase less detox of free radicals free radicals can kill the malarial parasite |
|
|
why parasite carries its own hexokinase
|
hexokinase is inhibited by pyruvate
parasitic hexokinase is not subject to negative inhibition |
|
|
Result of the lack of feedback inhibition on hexokinase
|
pyruvate is converted to lactate
lactic acidosis occurs |
|
|
Other than continuing glycolysis, where can G6P go, in the case of malarial infection
|
6-phosphogluconate --> ribose phosphate --> parasite RNA and DNA synthesis
|
|
|
Lactic acidosis can cause ______
|
coma
|
|
|
How the parasite makes RNA/DNA
|
ATP => hypoxanthine => parasite purines => RNA/DNA
|
|
|
RBCs use glycolysis or ETC
|
glycolysis
|
|
|
acidosis inhibits erythrocyte glycolysis
|
ok
|
|
|
Parasites can also make their own _____
|
NADPH through their own G6PDH
|
|
|
How does the parasite take over glycolysis
|
Its hexokinase is feedback inhibition resistant, since there is such high [pyruvate], the native hexokinase doesn’t function, while the parasitic hexokinase does
|
|
|
see pic of analine on p 7
|
ok
|
|
|
what happens to aniline based drugs in the body
|
oxidized by P450
|
|
|
aniline based drugs and G6PD deficiency
|
aniline drugs are oxidized by P450
then they can undergo redox cycling individuals with G6PD deficiency are particularly susceptible to this form of toxicity |
|
|
Drugs that induce hemolytic anemia in G6PD deficient individuals (8)
|
Aspirin
Chloroquine Dapsone Methylene blue napthalene Primaquine Salicyclates Sulfa drugs |
|
|
2 things that reduce malaria risk
|
sickle cell
G6PD deficiency |
|
|
component of fava beans
|
vicine
|
|
|
how to get rid of vicine
|
cook the beans
|
|
|
what happens to vicine in the stomach
|
low pH breaks it into glucose and divicine
|
|
|
what happens to divicine
|
cycling between reduced and oxidized forms
during oxidation it donates and electron to O2 making superoxide anion |
|
|
ultimate downstream effect of ROS in the RBC
|
hemolytic anemia
|
|
|
favism
|
hemolytic response to consumption of fava beans
have to be G6PD deficient for this to occur but not all G6PD deficient people show favism when exposed to the beans |
|
|
Where is sickle cell anemia common (order from highest to lowest prevalence)
|
Where there is lots of malaria
West Africa (25%) Afro-Caribbean African Americans Pakistan India Cyprus (1%) |
|
|
Mutation that makes sickle cell (at the gene and amino acid level)
|
Amino acid mutation (Glu -> Val)
Position 6 of the β chain Glutamate is charged, valine is hydrophobic It wants to exclude itself from water The Val hides within the α helical chain of other Hb molecules Could also be a Glu121Lys mutation - close to position 6 |
|
|
how the sickle cell mutation leads to pathology at the molecular level
|
normal cells until severe O2 stress occurs
Hb tetramers interact with each other in the deoxygenated state Hb tetramers bury themselves in one another in an organized way - form fibrils |
|
|
how many fibrils aggregate in sickle cells
|
14
|
|
|
sickle cell fibrils grow until ____
|
they encounter the BV wall
|
|
|
type of Hb in sickle cell disease
|
HbS
|
|
|
How sickle cells help defend against malaria
|
1. HbS is more readily oxidized. So more oxygen radicals are produced
2. RBC membrane is more leaky => K loss plasmodium grows well in high K |
|
|
Phenotype of homozygote vs. heterozygote for sickle cell
|
Homo = full blown sickling phenotype
Hetero = little phenotypic effect under normal circumstances |
|
|
Why sickle cells result in anemia
|
Abnormal cells are removed from circulation in the spleen
|
|
|
Prognosis of sickle cell disease
|
No good treatment
early death common |
|
|
Heterozygotes are said to possess
|
sickle cell trait
|
|
|
In vivo, sickling is triggered by
|
Prolonged capillary transit:
if lag time for fibre formation is longer than transit time from peripheral capillaries to the lung alveoli This happens when there is abnormal adherence to the endothelium, which is the case in inflammation (which can be caused by infection) |
|
|
How to ensure that capillary transit is speedy enough to prevent sickling
|
Aggressively prevent and treat primary infections
|
|
|
4 components of treating sickle cell disease
|
Manage vaso-occlusive crisis (including stroke)
Manage chronic pain syndromes Manage chronic anemia Prevent and treat primary infections |
|
|
Role of hydroxyurea in sickle cell disease
|
Promotes expression of altered globin chains that are not usually expressed - γ chain
this chain does not produce as ideal a binding site for val |
|
|
Why do people with HbS have shorter RBC lifetimes
|
Sickling does not necessarily occur. So it is mostly not due to the fact that sickle cells are more likely to be filtered out by the spleen
Instead it is because the low levels of K lead to cell death |
|
|
Thalassemia vs. sickle cell anemia
(wrt inheritance) |
Sickle cell = substitution of single specific amino acid in one Hb chain
Thalassemia is loss or substantial reduction of a single Hb chain |
|
|
Thalassemia
|
Group of diseases resulting from inherited defects in the rate of synthesis of one of the Hb chains
Result is low levels of functional Hb Decreased production of RBCs anemia |
|
|
Results of thalassemia
(3) |
ineffective erythropoiesis
hemolysis anemia |
|
|
Types of thalassemia
|
alpha and beta
|
|
|
alpha thalassemia
|
defect in alpha chain production
concomitant excess in Beta and gamma chain abnormal tetramers form |
|
|
what happens when there is a defect in alpha chain production
|
excess in beta and gamma chain
abnormal tetramers form |
|
|
what is weird about the tetramers that form in alpha thalassemia
|
high affinity for O2
no cooperativity release in tissues is poor |
|
|
what is produced in excess in beta thalassemia
|
alpha chains
|
|
|
how does the body deal with the lack of beta Hb chains in beta thalassemia (2)
|
1. continued production of fetal Hb
2. insoluble aggregates of alpha chains precipitate in immature RBCs |
|
|
HbF
|
2 alpha
2 gamma |
|
|
problems with thalassemia
|
1. eryhtocytes dont last as long
2. inefficient O2 delivery |
|
|
What happens with transfusion of thalassemic patients
|
Present with anemia
Physician gives blood transfusion Too much iron causes iron overload |
|
|
Allotransplatation
|
Transplantation of cells to a recipient from a genetically non-identical donor of the same species
|
|
|
2 possible treatments for thalassemia that are better than blood transfusion
|
Splenectomy
allogeneic hematopoietic stem cell transplantation |
|
|
How to manage iron overload
|
chelation
|
|
|
Major reservoirs of iron in the body (from most iron content to least iron content)
(3) |
blood
bone marrow liver |
|
|
How is iron stored (from most iron to least)
which proteins it is associated with (6) |
Hemoglobin
Myoglobin Cytochromes Fe/S enzymes Ferritin (iron bank) Transferrin (iron armored truck) |
|
|
% body iron bound in Hb
|
60
|
|
|
how much iron do we excrete
|
very little
|
|
|
Heintz bodies
|
inclusions that occur when there is lots of iron damage in a cell
commonly occurs in cells that have undergone lots of oxidative stress |
|
|
how our bodies protect us from iron damage
|
iron is bound to proteins
|
|
|
Electron donor = acid/base
|
base
|
|
|
What can happen to iron ions in the stomach
|
stomach = acidic
bases donate electrons stomach accepts electrons from iron, oxidizing the iron to Fe3+ |
|
|
what form of iron enters the intestinal cell
|
2+
|
|
|
how does iron enter the intestinal cell
|
+2 form transported by DMT1
or heme can also enter the cell |
|
|
reaction of heme breakdown
|
heme ---[heme oxygenase]--->biliverdin + Fe2+ + CO
|
|
|
Steps of iron absorption from the GI lumen
|
1. Proteolytic digestion releases iron/heme
2. Iron and heme are chelated by compounds that keep them soluble and available for absorption 3. Fe2+ may oxidize to Fe3+ in the acidic environment of the stomach 4. Ferroreductase has to reduce it back to Fe2+ in order for it to enter the cell 5. Iron enters the cell as either inorganic iron or heme. Inorganic iron is transported by DMT1 (divalent metal transporter 1). Unknown how heme crosses the membrane a. Heme is broken down into biliverdin, Fe2+, CO by heme oxygenase 6. Heme is degraded in absorptive cells by heme oxygenase to release inorganic iron |
|
|
In which section of the GI tract does iron absorption primarily occur
|
proximal duodenum
|
|
|
% of dietary iron that is absorbed
|
10
This is unusual compared to other substituents - the body grabs all the glucose it can |
|
|
the body can only absorb 10% of iron in the GI tract - implication of this
|
can't just give a patient a big dose of iron - have to dose them slowly over time
|
|
|
why nonheme (green plant) iron is hard for us to access
|
there are proteins in it that bind iron so tightly that we can't access it
|
|
|
What may happen when you have too much iron in the body
|
May be held in the gut mucosal cell they die frequently
|
|
|
What promotes iron absorption
|
vit C
|
|
|
Form that the intestinal mucosal cell stores iron
|
Fe3+ bound to ferritin
|
|
|
How does the intestinal mucosal cell convert iron to the +3 form in order to store it
|
hephaestin
|
|
|
what converts +3 to +2 to get it out of storage
|
DcytB
|
|
|
How is iron transported from inside intestinal mucosal cell to blood
|
hephaestin converts +2 to +3
ferroportin moves it onto transferrin in the blood |
|
|
free form of iron in cell
|
+2
|
|
|
Iron storage protein
|
ferritin
|
|
|
iron transport protein
|
transferrin
|
|
|
Role of hephaestin
|
Converts Fe2+ to Fe3+
|
|
|
2 places where hephaestin works
|
When converting free iron to the ferritin-stored form
When converting free iron to the transferrin-stored form |
|
|
Hephaestin converts Fe2+ to Fe3+ In mucosal cells, what enzyme does this job in other cell types
|
Ceruloplasmin
|
|
|
What happens to iron in infection
|
Pathogen => acute phase response
Acute phase response = group of proteins that is activated in response to infection Iron is locked down by hepcidin, which inhibits ferroportin and keeps the iron in the cell. This is because high iron levels are beneficial to the pathogen |
|
|
Role of hepcidin
|
Inhibits ferroportin - preventing the transport of iron out of the cell trapped iron is ultimately removed when cells are sloughed from the digestive tract
|
|
|
Role of hepcidin
|
Inhibits ferroportin - preventing the transport of iron out of the cell
trapped iron is ultimately removed when cells are sloughed from the digestive tract |
|
|
how does the body increase iron absorption
|
decrease hepcidin production
|
|
|
What is the effect of decreasing hepcidin
|
Ferroportin is not inhibited
iron can be transported from enterocyte to bloodstream |
|
|
Conditions which decrease iron absorption
|
systemic inflammation
|
|
|
how many Fe's are held by a single ferritin
|
4500
|
|
|
where is ferritin made
|
liver
|
|
|
structure of ferritin
|
very large
60% glycosylated |
|
|
Normally, ferritin is __% loaded
|
20
|
|
|
When do ferritin levels rise
|
Iron overload conditions
|
|
|
How is iron internalized (from the blood) by cells
|
Ferritin receptor endocytosis
|
|
|
In non-enterocyte cells, what catalyzes the conversion of Fe2+ to Fe3+ for binding to ferritin
|
ferroxidase
|
|
|
What happens in alcoholism wrt iron (3)
|
Decreased transferrin-bound uptake
Increased ferritin receptors Increased hepatocyte iron overload |
|
|
Purpose of glycosylation of ferritin
|
Protects it from immune system attacks - allows self-recognition
|
|
|
Which is larger: ferritin or transferrin
|
ferritin
|
|
|
Moles of Fe3+ carried per mole of transferrin
|
2
|
|
|
Where is transferrin synthesized
|
liver
|
|
|
% of transferrin that is carb
|
6
|
|
|
95% of the iron present from blood plasma comes from what source
|
RBC catabolism
|
|
|
% saturation that is overload for transferrin and ferritin
|
35
|
|
|
% saturation that is normal for transferrin and ferritin
|
20
|
|
|
Which cells have high levels of transferrin receptor (3)
|
Hepatocytes
bone marrow Placenta |
|
|
Transferrin isn't the only iron transporter but it transports ___% of the iron present in blood plasma
|
95
|
|
|
Structure of transferrin receptor
|
Carboxy terminus is extracellular
Short intracellular N terminal tails are critical for internalization |
|
|
Process of regulation of the transferrin receptor
|
When cellular Fe is low, TfR mRNA is stabilized and increased receptor synthesis occurs
When cellular Fe is high, TfR mRNA is destabilized, reduced receptor synthesis occurs |
|
|
process of internalization of the transferrin receptor
|
1. loaded transferrin binds its receptor
2. conformational change in receptor 3. intracellular proteins recruited 4. clathrin coated pits form 5. invagination and vesicle formation 6. endosome 7. protons are pumped in 8. transferrin releases iron 9. iron transported out of vesicle 10. recycling of receptor to the surface |
|
|
Curl
|
Compartment for the uncoupling of receptor-ligand complex
|
|
|
How do you acidify the compartment
|
ATP dependent proton pump
|
|
|
What is transferrin called when not bound to iron
|
apotransferrin
|
|
|
How iron is regulated at the gene(ish) level
|
Iron responsive proteins bind the mRNA of proteins involved in iron homeostasis
Binding of these proteins alters the translational efficiency of these mRNAs |
|
|
Which proteins have mRNAs that are regulated by iron responsive element binding proteins (3)
|
Ferritin
transferrin receptor aconitase |
|
|
What is the nucleotide sequence that iron responsive proteins bind to on mRNA called
|
iron responsive element
|
|
|
How are iron responsive elements structured in order to respond to iron responsive proteins
|
mRNA can form loops (think of tRNA clover)
|
|
|
Regulation of ferritin
|
increases when iron increases
Iron acts on IRE-BP IRE-BP alter conformation reduced affinity for IRE IRP released from 5' IER translation increases |
|
|
important - iron regulated proteins are regulated at the ___ not ___ level
|
translation
NOT transcription |
|
|
where are IREs in ferritin vs. transferrin receptor mRNA
|
ferritin: 5'
transferrin: 3' |
|
|
regulation of transferrin receptor
|
iron binds IRE-BP
IRE-BP changes conformation IRE-BP releases 3' polyA tail increased mRNA degradation |
|
|
important note about iron regulation
|
the changes in translation are relative to that cell
ie. high iron within the cell causes changes that lower free iron - so more is stored and less can enter |
|
|
high iron increases/decreases ferritin expression
|
increases
|
|
|
High iron increases/decreases transferrin receptor expression
|
decreases
|
|
|
Reasons for excessive RBC destruction
|
Dietary
Environment/drug induced Intrinsic - genetic, Thalassemia, HbS |
|
|
When pathological bleeding can occur
(6) |
ulcer
bleeding gums hookworm infection chronic hemodialysis hemorrhoids intestinal diseases |
|
|
problems associated with iron deficiency
|
Preterm birth
Impaired mental and motor development in children |
|
|
Agents that inhibit iron absorption (4)
|
Polyphenols - ex. tannates
Phytates Phytic acid |
|
|
source of phytates (3)
|
cereal
nuts legumes |
|
|
source of phytic acid (1)
|
soybeans
|
|
|
source of tannates
|
tea
coffee veg |
|
|
Vit C promotes the absorption of a particular type of iron
|
non heme
|
|
|
How vit C promotes absorption
|
Reduces Fe3+ to Fe2+
|
|
|
what term is used for the fact that only 5-10% of iron enters the enterocyte
|
mucosal block
|
|
|
who has less of a mucosal block
|
children
|
|
|
Problem with oral iron preparations
|
Increased iron in the enterocyte -->
Increase mucosal ferritin synthesis --> decreased transfer of iron to plasma ferritin |
|
|
Criteria involved in diagnosing iron deficiency
|
1. ↓ hemoglobin level
2. ↓ serum iron 3. ↓↓ serum ferritin 4. ↑ elevated serum transferrin 5. ↑ transferrin receptor ↑↑ protoporphyrin levels |
|
|
Which of the criteria has low specificity
|
Serum iron - lots of conditions other than iron deficiency will give you low serum iron
|
|
|
Which of the criteria has high specificity
|
Serum ferritin
|
|
|
Highly specific tests are reliable when their result is
|
positive
|
|
|
Why there is high transferrin when iron is low
|
The body is trying to get more iron into the tissue
|
|
|
Saturation of transferrin in iron deficiency
|
Low
|
|
|
what type of protein is hepcidin
|
acute phase protein
|
|
|
Why is Fe fortified formula not suitable for babies who are breastfeeding and less than 6 months
|
Reserve stores are sufficient
Mucosal block is not as developed May cause hemolysis in vit E deficient premature infants Excess iron causes hemolysis via oxidative stress (ex. Fenton rxn) |
|
|
what is not a source of iron
|
milk
|
|
|
supplementation with iron can be harmful for who
|
hereditary hemochromatosis
hemosiderosis (an iron overload disorder) |
|
|
risk with moderate increase in plasma iron levels
|
Cancer/ischemic heart disease
|
|
|
How milk and cheese can support iron uptake
|
lactoferrin can complexto non-heme iron
|
|
|
Who are parenteral iron preparations useful for
(3) |
Patients who don't absorb oral preparations (IBD, peptics ulcers)
People who get side effects People who are non-compliant |
|
|
Danger associated with parenteral iron administration (2)
|
Anaphylaxis
iron overload |
|
|
how to deal with anaphylaxis risk
|
identify patients prior to treatment
|
|
|
advantage of parenteral admin
|
dont have to worry about mucosal intelligence
|
|
|
3 examples of parenteral iron supplements
|
Iron dextran (polymatose) NEW
Iron dextran OLD - IV (some deep IM) - withdrawn due to lots of anaphylaxis Iron sorbitol OLD - IM (pain, myalgia, abscess formation) |
|
|
Adverse effects associated with oral iron supplementation
(3) |
Nausea
abdominal pain Constipation/diarrhea |
|
|
Problem with drugs and iron supplementation
|
Iron from oral preparations can complex with various drugs, reducing availability
|
|
|
Drugs that complex with iron resulting in reduced bioavailability
|
Tetracycline
Penicillamine quinoline Levodopa Methyldopa Levothyroxine Etidronate |
|
|
How to reduce side effects in oral iron supplements
|
don't take the whole dose at once
|
|
|
alcoholic cirrhosis can cause
|
iron overload
|
|
|
2 types of hemochromatosis
|
hereditary
induced |
|
|
how hereditary hemochromatosis is inherited
|
mutation of HFE gene
protein that interacts with the transferrin receptor prevents the transferrin receptor from working |
|
|
induced hemochromatosis
|
giving parenteral iron or transfusion
|
|
|
Who are often recipients of the transfusions that result in induced hemochromatosis
|
Thalassemia major
sickle cell |
|
|
Why individuals with hemochromatosis have a weird looking tan
|
iron shunting into the skin
|
|
|
Result of hemochromatosis
|
redox rxns damage organs
|
|
|
Organs particularly damaged by hemochromatosis
|
liver - cirrhosis
pancreas - diabetes |
|
|
why alcoholism associated with iron overload
|
Alcohol makes proteins associated with iron regulation
In alcoholism there is decreased transferrin bound iron uptake Increased ferritin receptors and increased hepatocyte iron overload |
|
|
Symptoms of severe iron overload
(9) |
Black stools
Lethargy Severe acidosis Convulsions Coma Circulatory collapse Bloody diarrhea Hepatic and renal failure Hypotension |
|
|
What happens in iron poisoning
|
Unbound serum iron rises due to saturation of transferrin
Free serum iron can accumulate in the liver |
|
|
When there is excess serum iron, where does it accumulate
|
Liver kupffer cells - special macrophages
bone marrow Myocardium Pancreas |
|
|
Why does iron accumulate in the pancreas
|
no active excretion mechanisms
|
|
|
Why myocardium
|
High levels of transferrin
|
|
|
Consequences of iron poisoning in different organ systems
|
Hepatomegaly - hepatoma
Liver cirrhosis Skin pigmentation Diabetes mellitus Hypogonadism Heart failure |
|
|
Anti-iron therapies
(2) |
phlebotomy (acute)
Desferoxamine chelation + ascorbate |
|
|
what is phlebotomoy
|
blood letting
|
|
|
Advantage of hemochromatosis (why allele persisted)
|
Prevents anemia under conditions of low iron diet
|
|
|
Sequence of events causing liver injury in iron overload
|
Hepatic parenchymal iron overload --->
Oxygen radicals Damage lipid membrane and proteins Lysosomal fragility Organelles under low pH will dump their contents organelle dysfunction When mitochondria are damaged, cytochromes are released into the cytoplasm This leads to cell death Lots of cell death = fibrosis, cirrhosis |
|
|
learn the chart on slide 40 lecture 3
|
okq
|
|
|
list 4 anticoagulants
|
warfarin
heparin apixaban dabigatran |
|
|
coagulation AKA
|
thrombogenesis
|
|
|
who needs anticoagulants
|
1. MI
2. arrthymia 3. prosthetic heart valves |
|
|
warfarin mechanism of action
|
vitamin K antagonist
interferes with synthesis of coagulation factors 2, 7, 9, 10 |
|
|
test that monitors tendency of blood to clot
|
PT/INR
|
|
|
safe INR
|
2-3
|
|
|
what happens below INR 2
|
thrombosis likely
|
|
|
role of heparin
|
indirect thrombin inhibitor
increases endogenous antithrombin activity |
|
|
apixaban mechanism of action
|
factor Xa inhibitor
|
|
|
dabigatran mechanism of action
|
thrombin inhibitor
|
|
|
what determines blood type
|
modification of H antigen by glycosyltransferase - this is encoded by the alleles (A,B,O) of the ABO gene
|
|
|
define agranulocytosis
|
reduced granulocytes in the blood
|
|
|
granulocytes
|
neutrophils
eosinophils basophils mast cells |
|
|
agranulocytosis is usally caused by ___
|
drugs
|
|
|
common agranulocytosis inducing drugs
|
DAPSONE
anti-inflammatory anti-thyroid cardiovascular procainamide psychotropic (TC antidepressants) antibiotics dermatological MAbs |
|
|
signs and symptoms of agranulocytosis
|
often asymptomatic
sudden fever sore throat sepsis increased chance of infection |
|
|
2 mechanisms of pathogenesis of agranulocytosis
|
1. direct toxicity
2. immune mediated |
|
|
how "Direct toxicity" agranulocytosis works
|
conversion of the drug into a reactive metabolite that irreversibly binds to neutrophils and their bone marrow precursors and kills the cell
|
|
|
how "immune mediated" agranulocytosis works
|
1. drug adsoprtion
2. innocent bystander 3. protein carrier 4. autoimmune |
|
|
treatment of agranulocytosis
|
hematopoietic growth factors:
granulocyte colony stimulating factor (G-CSF) granulocyte macrophage colony stimulating factor (GM-CSF) |
|
|
basophil
|
release inflammation promoting chemicals
|
|
|
eosinophils
|
kill parasite infected cells
|
|
|
neutrophils
|
phagocytose and kill bacteria
|
|
|
monocytes/macrophages
|
APCs
activate helper T cells |
|
|
what do macrophages activate
|
helper T cells
|
|
|
B-lymphocytes
|
have not come into contact with their antigen yet
|
|
|
plasma cells
|
activated B lymphocytes (have seen their antigen)
produce antibdoies |
|
|
memory B cells
|
inactive B cells that wait for secondary exposure
|
|
|
helper T cells
|
release cytokines to help activate B lymphocytes
|
|
|
cytotoxic T cells
|
kill cells carrying forieng antigens by inducing apoptosis and secreting digestive enzymes and perforin
|
|
|
how cytotoxic T cells kill
|
induce apoptosis
secrete digestive enzymes secrete perforin |
|
|
NK cells
|
target abnormal self cells and induce apoptosis
|
|
|
Sirolimus is what kind of name
|
generic
|
|
|
what is the natural product name of Siroimus
|
rapamycin
|
|
|
what is the brand name of sirolimus
|
rapamune
|
|
|
sirolimus is lipophilic/hydrophilic
|
lipophilic
|
|
|
class of molecule that sirolimus is
|
lipophilic macrocyclic lactone
|
|
|
how old you have to be to take sirolimus
|
13
|
|
|
indication of sirolimus
|
kidney transplant rejection prevention
|
|
|
dosage form of sirolimus
|
tablet/liquid
|
|
|
mechanism of action of SIrolimus
|
in T and B cells
binds FKBP FKBP-Sirolimus complex binds mTOR normally: mTOR promotes expression of proteins involved in cell growth and proliferation THis is suppressed |
|
|
absorption of Sirolimus
|
rapid from GI tract
|
|
|
distribution of Sirolimus
|
bloodstream
|
|
|
metabolism of Sirolimus
|
3A4 and pgp
O-demethylation and hydroxylation intestinal wall and liver |
|
|
Sirolimus is primary excreted by
|
feces
|
|
|
symptoms of arsenic poisoning
|
headache
drowsiness diarrhea vomiting bloodly urine convulsions change in fingernail pigmentation |
|
|
how arsenic enters the body
|
inhalation and/or ingestion
|
|
|
where does arsenic go in the body
|
liver
|
|
|
metabolism of arsenic
|
methylation to MMA and DMA
|
|
|
why arsenic is carcinogenic
|
oxidative stress
inhibition of p53 genotoxicity altered DNA repair mechanisms |
|
|
arsenite
|
As3+
|
|
|
what arsenite does
|
reacts with thiols and sulhydryl groups
inhibits GSH reductase inhibits pyruvate dehydroxygenase (result is decreased ATP production and gluconeogenesis) |
|
|
arsenate
|
As5+
|
|
|
As5+ and As3+
|
3 = arsenite
5 = arsenate |
|
|
what does arsenate do
|
replace phosphate groups because of similar structure
ADP forms ADP-arsenate instead of ATP glucose-6-arsenate instead of G6P glyceraldehyde-3-arsenate instead of G3P |
|
|
treatment of arsenic poisoning
|
DMSA
|
|
|
Warburg effect
|
preferred metabolic pathway exhibited by cancerous cells -> oxidative glycolysis
|
|
|
which vitamin is unstable when cooked or stored
|
folic acid
|
|
|
liver and bone marrow take up lotsof ____
|
5 methyl THF
|
|
|
type of inhibition - methotrexate and aminoptrerin
|
competitive
|
|
|
which form of vit b12 is used for methylation (homocysteine -> methionine)
|
CH3 - methylcobalamin
|
|
|
which form of vit B12 is used for cyanide and hydrogen sulfide antidote
|
OH - hydroxocobalamin
|
|
|
which form of vit B12 is used for amino acid metabolism
|
Ado - 5'deoxyadensylcobalamin
|
|
|
WHICH form of vit B is used for supplement
|
cyanocobalamin
|
|
|
role of conjugase
|
converts folate polyglutatmate to polymonoglutatmate in the intestinal lumen
|
|
|
cofactor for conjugase
|
Zn
|
|
|
purine synthesis - beginning andend of the pathway
|
ribose-5-phosphate
inosine |
