Term
| Where does glycolysis take place in the cell? |
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Definition
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Term
| What is the rate-limiting enzyme of glycolysis? |
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Definition
phosphofructokinase (PFK-1)
(catalyzes F-6-P to F-1,6-P)
+ regulators: AMP, fructose-2,6-BP
- regulators: ATP, citrate |
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Term
| Where does gluconeogenesis take place in the cell? |
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Definition
both mitochondria and cytoplasm (liver, kidney, intestine)
-first step takes place in the mitochondria (pyruvate to oxaloacetate catalyzed by pyruvate carboxylase)
-the rest of the rxns take place in the cytosol |
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Term
| What is the rate-limiting enzyme of gluconeogenesis? |
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Definition
Fructose-1,6-bisphosphatase
+ regulators: ATP
- regulators: AMP, fructose-2,6-BP |
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Term
| Where does the TCA cycle take place in the cell? |
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Definition
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Term
| What is the rate-limiting enzyme of the TCA cycle? |
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Definition
Isocitrate dehydrogenase
(catalyzes isocitrate to a-ketoglutarate)
+ regulators: ADP
- regulators: ATP, NADH |
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Term
| Where does glycogenesis and glycogenolysis take place in the cell? |
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Definition
| cytoplasm (muscle, liver, adipose tissue) |
|
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Term
| What is the rate-limiting enzyme of glycogenesis? |
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Definition
glycogen synthase
(adds glucose units to nonreducing ends of existing glycogen chain in alpha-1,4 linkages)
+ regulators: glucose, insulin
- regulators: epi, glucagon |
|
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Term
| What is the rate-limiting enzyme of glycogenolysis? |
|
Definition
glycogen phosphorylase
(breaks alpha-1,4 linkages)
+ regulators: AMP, epi, glucagon
- regulators: insulin, ATP |
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Term
| Where does the HMP shunt (pentose-phosphate pathway) take place in the cell? |
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Definition
| cytoplasm (liver, adrenal cortex, lactating mammary glands) |
|
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Term
| What is the rate-limiting enzyme of HMP shunt? |
|
Definition
glucose-6-phosphate dehydrogenase (G6PD)
(catalyzes G-6-P to 6-phosphogluconate using NADP+)
+ regulators: NADP+
- regulators: NADPH |
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Term
| Where does de novo purine and pyrimidine synthesis take place in the cell? |
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Definition
| cytoplasm in cells of all tissues |
|
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Term
| What is the rate-limiting enzyme of de novo pyrimidine synthesis? |
|
Definition
carbamoyl phosphate synthetase II
(catalyzes the combination of CO2 with glutamine to form carbamoyl phosphate)
+ regulators: UTP
- regulators: ATP PRPP |
|
|
Term
| What is the rate-limiting enzyme of de novo purine synthesis? |
|
Definition
glutamine-PRPP amidotransferase
(catalyzes an addition of an alpha-amino group to PRPP from glutamine to form 5-phosphoribosylamine)
+ regulators: none
- regulators: AMP, IMP, GMP
*MTX is a folic acid analog that inhibits the formation of THF, thus interferes with de novo purine synthesis |
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Term
| Where does the urea cycle take place in the cell? |
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Definition
| both mitochondria and cytoplasm |
|
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Term
| What is the rate-limiting enzyme the urea cycle? |
|
Definition
carbamoyl phosphate synthetase I
(catalyzes formation of carbamoyl phosphate from NH4+, CO2, and ATP)
+ regulators: N-acetylglutamate |
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Term
| Where does fatty acid synthesis take place in the cell? |
|
Definition
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Term
| What is the rate-limiting enzyme in fatty acid synthesis? |
|
Definition
acetyl-CoA carboxylase (ACC)
(catalyzes the conversion of acetyl CoA to malonyl CoA)
+ regulators: insulin, citrate, glucagon
- regulators: palmitoyl-CoA |
|
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Term
| Where does fatty acid oxidation (B-oxidation) take place in the cell? |
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Definition
|
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Term
| What is the rate-limiting enzyme in fatty acid oxidation? |
|
Definition
Carnitine acyltransferase I
(catalyzes the transfer of a fatty acyl to carnitine which is able to cross the mitochondrial membrane)
- regulators: malonyl-CoA |
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Term
| Where does ketogenesis occur in the cell? |
|
Definition
|
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Term
| What is the rate-limiting enzyme in fatty acid oxidation? |
|
Definition
HMG-CoA synthase
(catalyzes the production of HMG CoA from acetyl CoA and acetoacetyl CoA) |
|
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Term
| Where does cholesterol synthesis occur in the cell? |
|
Definition
|
|
Term
| What is the rate-limiting enzyme in cholesterol synthesis? |
|
Definition
HMG-CoA reductase
(catalyzes the production mevalonic acid from HMG CoA)
+ regulators: insulin, thyroxine
- regulators: glucagon, cholesterol |
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