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62 Cards in this Set
- Front
- Back
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4 ENZYMES in 4 repeating steps of BETA-OXIDATION
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Acyl CoA dehydrogenase
enoyl CoA hydratase beta-hydroy-acyl-CoA DH ketothiolase |
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oxidizing palmitoyl CoA (C16:0) would require ___ cycles and would yield ____, ____, _____
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7 cycles of beta-oxidation
and would yield 8 AcCoA, 7 FADH2, 7 NADH |
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Summarize goal and mechanism of action for CARNITINE SHUTTLE
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Goal: transport FAs into mitochondrial matrix
Action: swap canitine for acyl-carnitine and release CoA, then acyl-carnitine moves into matrix |
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How are FAs activated?
Addition of: Location: Enzyme: Uses: ____ drives reaction. |
FAs activated by addition of CoASH
In cytosol, on outer mitochondrial matrix Catalyzed by FATTY ACYL-CoA SYNTHETASE PPi --> 2Pi drives reaction |
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Net reaction for the synthesis of palmitate (C16)
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AcCoA + 7 malonyl CoA + 14 NADPH + 20H+
--> palmitate + 7CO2 + 14NADP+ + 8CoA + 6H2O |
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Net reaction for malonyl synthesis
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7 AcCoA + 7 CO2 + 7ATP
--> 7 malonyl CoA + 7ADP + 7Pi + 14H+ |
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Goal of malate/citrate/pyruvate shuttle
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Tansport AcCoA from mitochondrial matrix to cytosol
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β-ketoacyl ACP synthase
β-ketocyl-ACP reductase β-hydroxyacyl-ACP dehydratase enoyl-ACP reductase |
4 repeated steps of FATTY ACID SYNTHESIS
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β-ketothiolase
HMG-CoA synthase HMG CoA lyase β-hydroxybutarate dehyrogenase |
KETONE BODY SYNTHESIS
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acyl CoA dehydrogenase
enoyl CoA hydratase β-hydroxy-acyl CoA dyhydrogenase β-ketothiolase |
4 repeated steps of BETA-OXIDATION
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omega 6, aka: _____
omega 3, aka: _____ are the precursors for _____ which is used to make _____ and _____ |
Linolenic acid (omega 3) and linoleic acid (omega 6) are the precursors of ARACHIDONIC ACID, which is used to make PROSTAGLANDINS and LEUKOTRIENES
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Where does further processing of palmitate take place?
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cytoplasmic face of E.R.
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Enzyme catalyzing committed step in FA synthesis
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Acetyl CoA carboxylase
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How many ATP from 1 mol NADH?
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3 ATP
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How many ATP from 1 mol FADH2
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2 ATP
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How many ATP from 1 mol GTP
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1 ATP
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acyl CoA dehydrogenase
Substrate--> Product Coupled reaction |
Oxidizes: acyl CoA --> enoyl CoA
Reduces: FAD --> FADH2 |
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enoyl CoA hydrolase
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Hydrates enoyl CoA --> 3-hydroxy-acyl-CoA
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3-hydroxy-acyl-CoA dehydrogenase
(Coupled rxn?) |
Oxidizes 3-hydroxy-acyl-CoA --> 3-keto-acyl-CoA
Reduces: NAD+ --> NADH + H+` |
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3-ketothiolase
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aka: thiolase
Cleaves 3-keto-acyl CoA to Acetyl CoA with add'n of CoASH |
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methylmalonyl CoA mutase
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converts methylmalonyl CoA --> succinyl CoA
used in beta-oxidation when odd number of carbons in acyl chain REQUIRES Vitamin B12 |
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enoyl CoA isomerase
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moves double bond in acyl chain so that beta-oxidation can continue
(e.g.: cis, but trans needed) |
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Regulation of CAT I
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regulates entry of FAs into mitochondrial matrix
CAT I inhibited by high concentrations of MALONYL CoA |
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Regulation of LIPASES
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Starvation --> epinephrine/glucagon --> stimulation of lipases --> free FA level increase
"Fed" state --> insulin --> inhibition of lipases |
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MCAD deficiency
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Medium chain fatty acyl CoA dehydrogenase deficiency
4 v. specific DH enzymes catalyzing Step 1 of beta-oxidation for medium chain FAs common inborn error metabolism, leads to HYPOglycemia tx = carb-rich diet |
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All carbons in ketone bodies come from ...
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Acetyl CoA
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Entry of Acetyl CoA into TCA cycle depends on...
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OAA availability for citrate formation
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Low OAA concentrations lead to ACTIVATED _________
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PYRUVATE CARBOXYLASE
(GNG Pathway) |
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If GNG predominates, OAA is NOT going to...
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go to the TCA cycle to make citrate!
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So, OAA is being diverted to make glucose annd FAs are being oxidized to make Ac
CoA. What happens to the AcCoA? |
Without OAA, AcCoA is diverted to form:
acetoacetate beta-hydroxybuterate acetone |
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Where are ketone bodies excreted?
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URINE
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WHERE does fatty acid synthesis occur?
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CYTOSOL
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Three parts of FA Synthesis
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(1) AcCoA to cytosol by way of citrate (malate/citrate/pyruvate shuttle)
(2) AcCoA --> malonyl CoA, catalyzed by ACETYL CoA CARBOXYLASE (3) Chain growth by head-to-tail CONDENSATION |
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4 steps in FA synthesis (reaction types)
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(1) condensation
(2) reduction (3) dehydration (4) reduction |
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Carbon precursors to FA synthesis
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Acetyl-CE (condensing enzyme)
Malonyl-ACP (acyl carrier protein) |
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Besides moving AcCoA to cytosol, the m/c/pyr shuttle also...
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generates NADPH
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Committed step of FA synthesis
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Formation of Malonyl CoA
(from AcCoA) |
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Enyzme catalyzing committed step of FA synthesis
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acetyl CoA carboxylase
ATP DEPENDENT NOT part of FAS complex! |
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Cofactor for enzyme catalyzing committed step of FA synthesis
(and what does this cofactor do?) |
Biotin
(carries CO2 group) |
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FAS complex
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Fatty Acid Synthase complex
contains 7 enzymes for FA synthesis 6 enzymes - 1 for each 2C add'n 1 enzyme cleaves final 16C product NOT ATP dependent! |
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FA Oxidation
1st Substrate: Enzyme: Cellular Inhibitor of enzyme: |
Palmitoyl CoA
CAT I Malonyl CoA |
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FA synthesis
1st Substrate Enzyme: Cellular Inhibitor of enzyme: |
Malonyl CoA
Acetyl CoA carboxylase Palmitoyl CoA |
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In the reciprocal regulation of FA oxidation and FA synthesis, the ____ of each pathway _____ the ______ of the other
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In the reciprocal regulation of FA oxidation and FA synthesis, the FIRST SUBSTRATE of each pathway INHIBITS the FIRST ENZYME of the other pathway.
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Comitted Step of Cholesterol Synthesis
Enzyme: Substrate: Product: Coupled Reaction: |
HMG-CoA reductase
HMG-CoA Reductase HMG-CoA Mevalonate 2NADPH + 2H+ --> 2 NADP+ + CoASH |
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Two beta ketothiolase isoenzymes
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Mitochondiral matrix
(beta-oxidation and ketone body synthesis) Cytosolic (cholesterol synthesis) |
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WHERE is cholesterol synthesized?
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Cytosol of all cells
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The FIRST two steps of which two pathways are identical?
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Steps 1 and 2 of
KETONE BODY SYNTHESIS CHOLESTEROL SYNTEHSIS |
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Phosphorylation _______ HMG CoA reductase
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INACTIVATES
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Desphosphorylated HMG-CoA reductase is __________
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ACTIVE
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What molecule has identical regulatory effects on HMG-CoA reductase as cholesterol itself?
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CHOLIC ACID
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2 ways cholesterol inhibits its own synthesis pathway
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inhibits synthesis of HMG-CoA reductase
stimulates degradation of HMG-CoA redutase protein |
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Cholesterol _____ LDL receptor synthesis
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SUPPRESSES
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Define cholic acid
& where is it found? |
bile acid, catabolic product of cholesterol
found in liver and intestine |
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Most common clinical problem with cholesterol synthesis
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HYPERCHOLESTEROLEMIA
defect in cholesterol uptake due to defective LDL receptors tx: inhibit chl synthesis with structural analogs of HMG-CoA (e.g.: statins) as competitive inhibitors of HMG-CoA reductase |
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3 groups of cholesterol product
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Vitamin D
Steroid hormones Bile acids and bile salts |
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Define BILE ACID
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24C catabolic products of cholesterol with -OH groups at specific positions
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Define BILE SALT
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bile acids conjugated to glycine or taurine before leaving the liver
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Function of bile acids and salts
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POWERFUL DETERGENTS
igestion and absorption of lipids |
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Committed step of bile acid synthesis
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cholesterol --> 7-alpha-hydroxycholesterol
Enzyme: cholesterol 7-alpha-hydroxylase |
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What part of the cholesterol molecule yields lipid soluble vitamins?
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ISOPRENE UNIT
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List the lipid soluble vitamins
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A (Retinol), D (Cholecalciferol), E (alpha-tocopherol), K (phylloquinone)
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Pathophysiology of gallstones
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DECREAESED bile acid synthesis
--> INCREASED biliary cholesterol excretion more cholesterol enters bile than can be solubilized by bile salts --> cholesterol precipitates as gallstones |
