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38 Cards in this Set

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  • Back
In terms of metabolism, what is insulin responsible for in a fed state?
1. Uptake of carbohydrates
2. Metabolism of lipolipids
Where do you find fatty acid synthase?
In the cytoplasm
What the @#$% is going on here?
Answer
Fatty acid synthesis takes many steps with how many enzymes?
Just one
How do you elongate fatty acids with how many added carbons each time?
Sequential additions of malonyl CoA, and release of CO2. Thus 2 carbons added each time.
Fatty acid synthesis ends with formation of what? How many carbons is this molecule?
Palmitate (16 carbons)
What enzyme is responsible for forming malonyl-CoA and what special molecule is on it?
Acetyl CoA Carboxylase containing biotin.
How does malonyl-CoA get formed?
Acetyl-CoA carboxylase adds a carbon on to acetyl-CoA from HCO3-
During a fed state, what molecule does what to the regulation of malonyl-CoA formation?
Insulin activates formation of citrate to acetyl-CoA
During a fasting state, what molecules signal what to the regulation of malonyl-CoA formation?
Glucagon and epinephrine inhibit Acetyl-CoA carboxylase
Give an example of feed-forward activation for malonly-CoA formation.
High levels of citrate will activate Acetyl-CoA carboxylase.
Give an example of feedback inhibition for malonly-CoA formation.
Palimate inhibits Acetyl-CoA carboxylase
What are all the activators of malonyl-CoA formation?
1. Citrate
2. Insulin
What are all the inhibitors of malonly-CoA formation?
Palmitate, Epinephrine, and Glucagon.
Palmitate elongation occurs where?
Smooth ER
T/F - Palmitate elongation and fatty acid synthesis occurs using the same enzymes.
False - although both use malonyl CoA to contribute the carbons, the enzymes are different
Acetyl-CoA is formed in mitochondria and fatty acid syntheisis occurs in the cytoplasm. What allows acetyl-CoA to get to cytoplasm?
Acetate shuttle
or
Citrate cleavage pathway
In the acetate shuttle, what does citrate break down into?
Acetyl-CoA and oxaloacetate
How does oxaloacetate re-enter the mitochondria?
Must be reduced to malate or pyruvate to enter the mitochondria
Conversion of oxaloacetate to malate yields what?
NADH
Conversion of oxaloacetate to pyruvate yields what?
NADH and NADPH
Conversion of malate to pyruvate yields what?
NADPH
What is the enzyme responsible for forming NADPH from malate to pyruvate?
malic enzyme
Is cholesterol required in the diet?
No. All cells can synthesize it from simple precursors
What is the enzyme catalyzing the final step in cholesterol synthesis?
7-dehydrocholesterol D7 Reductase
What is the disorder associated with a defect or absence of 7-dehydrocholestrol D7 Reductase?
Smith-Lemli-Opitz syndrome (SLOS)
What is the beginning precursor of cholesterol?
Acetyl-CoA
General description of stage 1 of cholesterol synthesis.
3 Acetyl CoA form Mevalonate
General description of stage 2 of cholesterol synthesis.
Mevalonate conversion to Isoprolene
General description of stage 3 of cholesterol synthesis.
6 Isoprolene (5C) forms Squalene
General description of stage 4 of cholesterol synthesis.
Squalene goes through cyclization and subsequent modifications to form cholesterol.
What is the first committed step in cholesterol synthesis?
HMG-CoA (3 acetyl CoA condensed together) will be reduced to mevalonate with the help of HMG CoA reductase
What three things regulate the biosynthesis of cholesterol?
1. Intracellular cholesterol concentration.
2. Insulin
3. Glucagon
How does cholesterol take part in it's own feedback inhibition?
Cholesterol (or one of it's derivative) will inhibit GENE TRANSCRIPTION or activate DEGRADATION of HMG CoA Reductase
What phosphorylates HMG-CoA Reductase, and what does this do?
Glucagon phosphorylates it to inactivate HMG CoA Reductase.
What dephosphorylates HMG-CoA Reductase, and what does this do?
Insulin dephosphorylates it to activate HMG-CoA Reductase.
Cholesterol is primarily made where?
Liver
What are the two forms that cholesterol is exported in from the liver?
1. Bile salts
2. Cholestryl esters (lipoproteins)