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25 Cards in this Set
- Front
- Back
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What's the basic building block of fatty acid synthesis?
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Acetyl CoA via citrate
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Where does fatty acid synthesis occur?
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In the cytosol of hepatocytes
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How is acetyl CoA transferred to the cytosol of hepatocytes
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It's first converted to citrate in the mitochondrial matrix, transported, and converted back to acetyl CoA
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What' s the signal for the sythesis of fat?
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insulin (occurs in the FED state)
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What cytosolic enzyme involved in fat synthesis splits citrate back into OAA and acetyl CoA along with the hydrolysis of 1 ATP?
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citrate lyase
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What cytosolic enzyme involved in fat synthesis converts malate to pyruvate (and relases CO2), utilizing NADP+ in the process?
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malic enzyme
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Why is the synthesis of malic enzyme and citrate lyase induced during the fed state?
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insulin has positive transcriptional effect on these cytosolic enzymes
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What are two ways that NADPH is produced?
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through the oxidative portion of the pentose phosphate pathway and through the action of malic enzyme on malate
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What's the rate limiting first step in fatty acid synthesis?
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Conversion of acety CoA to malonyl CoA via acetyl CoA carboxylase (utilizes biotin, CO2, and ATP)
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How does insulin control the first step of fatty acid synthesis?
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It dephosphorylates acetyl CoA carboxylase, thereby activating it (glucagon & epinephrine has the opposite effect via Protein Kinase A)
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How is the first step of fatty acid synthesis influenced by allosteric control?
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citrate provides feed forward activation and palmitoyl CoA provides feedback inhibition
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What enzyme elongates a fatty acid by way of a malonyl CoA donor?
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fatty acid synthase complex
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What are the basic structural changes that must occur to a donated malonyl CoA as it runs through one cyle of fatty acid chain elognation?
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decarboxylation, a reductive step that converts a carbonyl to an alcohol via NADPH, a hydrolysis of an alcohol to an alkene, and a reduction of an alkene to an alkan via NADPH
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When does a fatty acid chain dissociate from the fatty acid synthase complex?
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When it is 16 carbons long (palmitoyl CoA)
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What cirtical subunit of the fatty acyle CoA complex resembles CoA?
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4-phosphopantetheine
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Where does elongation of a fatty acid chain greater than C16 take place?
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in the smooth endoplasmic reticulum
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How do we synthesize unsaturated fatty acids?
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via fatty acyl CoA desaturase (requires O2, NADH, and cyt b5
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Where do humans have difficulty inserting double bonds and what are some of the essential fatty acids?
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toward the end of the fatty acids, omega 3's, linoleic, linolenic, and docosohexaenoic acid (DHA)
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How is arachadonic acid synthesized?
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it's synthesized from linoleic acid via the addition of a double bond, a 2 carbon unit, and another double bond
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How are triglycerides synthesized?
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triglycerid synthesis can occur in either the liver or adipose; it basically involves the conversion of DHAP (or glycerol in the liver) to glycerol-3-phosphate along with the addtion of two fatty acyl CoA's from the liver to make a diacylglycerol (after removal of the third phosphate). Then the third fatt acyl CoA is added to make the triacylglycerol or triglyceride.
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How are triglycerides exported from the liver?
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via VLDLs
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What apoB do VLDLs use?
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apoB 100
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How are fatty acids delivered to muscle or adipose via VLDLs?
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They encounter an LPL that is activated by CII on the target cell and this hydrolyzes the fatty acids off the triglyceride for aborption (glycerol is returned to the liver)
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How does insulin promote triglyceride synthesis in adipose?
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It promotes glucose internalization which leads to the formation of DHAP and glycerol-3-P and stimulates the synthesis of the VLDL and its subsequent hydrolysis
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What are some critical cofactors for fatty acid metabolism?
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biotin, pantothenic acid, niacin (NADPH and NADH), and riboflavin (FADH2)
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