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23 Cards in this Set
- Front
- Back
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How is fructose metabolism different from glucose?
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1 transport of F not insulin dependent
2 F doesn't stimulate insulin secretion 3 phosphorylated by different kinases 4 Metabolism requires aldolase B 5 F bypasses critical regulated step in glycolysis |
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The bodies decreased release of what substance after a high fructose meal is said to be potential link between HFCS consumption and obesity epidemic?
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Leptin
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What are kinases that phosphorylate fructose and glucose?
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Fructokinase F> F-1-P
Found primarily in liver, intes mucosa and kidney Glucose- Hexokinase |
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What enzyme is required to cleave Fructose 1-P?
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Aldolase B
Frucotse-1-P--> Glyceraldehyde + DHAP Aldolase B found in same tissues as fructokinase |
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Why is Fructose more lipogenic than glucose?
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Because Fructose bypasses PFK-1 phosphofructokinase-1
Transition back to glucose--> glycogen can't occur. And results in Glycerol-3-Phosphate + FA --> TRIGLYCERIDE production |
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What pathway allows the body to endogenously synthesize fructose from glucose?
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Polyol Pathway
Glucose--1-->Sorbitol--2--> Fructose 1.Aldose Reductase 2.Sorbitol Dehydrogenase |
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Where does polyol pway occur?
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Seminal vesicles where spermatozoa use fructose
Aldose Red. found in lens, retina, nerve, liver, kidney Pway thought to cause complication in diabetes |
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What enzyme does the eye (retina, lens) kidney and nerve cell lack that results in mechanism of cell death?
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Under hyperglycemic condition lot of glucose enters and converted to Sorbitol. The aformentioned cells have very little SORBITOL DEHYDROGENASE
Build of sorbitol leads to cell swelling and believed to be associated with cataract formation, peripheral neuropathy and other complictn of diabetes. |
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What are disorders of Fructose metabolism?
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Essential Fructosuria- fructokinase defic. BENIGN, fructose accumulated and secreted in urine
Hereditary fructose intolerance- ALDOLASE B def., vomiting, intestinal discomfort, hypoglyc, failure to thrive, heptomegaly, Fructose detected in urine, lead to hepatic/renal failure, death, TX: no fruit, table sugar, sweets |
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Where does galactose enter glycolysis?
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Galactose> G-1P> Glucose-1-P--------8---> Glucose-6-P---> Pentose Phosphate Pway or glycolysis or glucose
8: Phosphoglucomutase |
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What are potential disoders of galactose metabolism?
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Nonclassical galactosemia
Galactokinase Def. Classical Galactosemia GALT Def. |
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What happens when galactokinase deficient?
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Galactose is converted to GALACTITOL
accumulation of galactitol causes CATARACTS |
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What happens when GAL-1-P URIDYL TRANSFERASE (GALT) deficient?
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Classical Galactosemias Causes cataracts and severe liver damage
TX: elimination of garlactose from diet (Breastfeeding must be STOPPED-soy based formula instead) |
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Where does the PPP occur? What does it make?
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Cytosol
Makes NADPH and ribose-5-P for nucleotide synthesis Most common inherited metabolic defect involves this pathway |
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What all does PPP provide NADPH?
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Reductn Glutathione, FA/Chol synth, cyt p450 system, phagocytosis, and NO syntheis.
Plus only way RBC make NADPH |
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Descrive PPP?
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Glucose-6P > Ribulose 5-P provides lots of NADPH
R-5-P> Ribose 5-P for nucleotide synth. Ribose-5-P>G3P for glycolysi via transketolase/TPP |
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What reaction of PPP are irreversible?
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Oxidative rexn that produce NADPH
by Glucose 6P dehydrogenase rate limiting step NADPH inhibitor of G6PD G6PD expressn ^ by insulin Ensures that in fed state, u have plenty of NADPH for FA synthesis |
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What products can nonoxidative rxn produce? Reversible?
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Ribose 5P for nucleotide synth
G3P Fructose-6-P Yes reversible in case there is high NADPH/NADP+ ratio |
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What cofactor does transketolase require? What rxn does it catalyze?
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TPP
Ribose5-P> Glyceraldehyde3P |
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What deficiency is being measured with a transketolase test?
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Thiamine deficiency
Measure TK activity then add thiamine to blood sample and see if TK activity has increased if it does pt deficient in thiamine |
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What enzyme def. is most common dz causing Enz defic?
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Glucose-6-Phosphate Dehydrogenase
X-linked causes hemolytic anemia RBC are most affected because the PPP is only means they have of making NADPH Not always symptomatic |
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G-6-PD deficiency symptoms can be precipatated by ? other factors?
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oxidative stress
certain oxidizing drugs Fava Beans (Favism) Symptoms are seen because RBC dont have enough NADPH to generate reduced GLUTATHIONE |
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What is histological hallmark of G-6-PD?
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When RBC doesn't have enough NADPH to reduce oxidizing agents, MetHb forms and results in HEINZ BODIES
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