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42 Cards in this Set

  • Front
  • Back
What kind of reaction is involved in most catabolic pathways?
Oxidative degradation (loss of electrons)
What kind of reaction is involved in most anabolic pathways?
Reductive biosynthesis (gain of electrons)
*NADPH required
Where do the synthetic (anabolic) reactions take place?
In the cytosol
Where do the catabolic reactions take place?
In the mitochondria
What are the high-energy bonds in ATP?
phosphoanhydride bonds, each ATP molecule has two of them.
What vitamin precursor is NADH derived from?
Nicotinate (niacin) Vitamin B3
What vitamin precursor is FADH2 dervied from?
Riboflavin (vitamin B2)
What is the reactive site of NAD+?
the nicotinamide ring. It can accept one hydrogen and two electrons (hydride ion)
What is the reactive site of FAD?
The flavin ring. It accepts two protons and two electrons.
What is the reactive site of Coenzyme A
The terminal sulfhydryl group. A high energy thioester bond is formed with the acyl group. This is a derivative of pantothenic acid (Vit B5)
What are the products of glycolysis?
2 ATP, 2 NADH, and 2 pyruvate molecules. (2 ATP are used in this rxn as well) This all happens in the cytosol
What are the 3 ways of regulating metabolic processes?
Controllin the amounts of enzymes, controlling catalytic activity, and controlling the accessibility of substrates
What is the first irreversible reaction in glycolysis?
Phosphorylation of glucose by hexokinase to glucose-6-phosphate (ATP used)
Enzyme only found in the liver that dephosphorylates glucose-6-phosphate?
Glucose-6-phosphatase. This enzyme is essential for the liver to maintain blood glucose.
What is the second irreversible rxn in glycolysis?
The phosphorylation of fructose-6-phosphate to make F 1,6-BP by phosphofructokinase-1. This is also the rate-limiting step of glycolysis.
What is pyruvate dehydrogenase?
Synthesizes acetyl CoA from pyruvate (key irreversible step) It is inhibited by NADH, acetyl CoA, and ATP. It is stimulated by pyruvate and ADP.
What is the first irreversible step of the TCA cycle?
Condensation of acetyl-CoA and oxaloacetate to form citrate. This is catalyzed by citrate synthase, the pace setting enzyme of TCA cycle.
If energy charge is high in the cell, how does this affect TCA?
oxaloacetate will go to glucose via gluconeogenesis
If energy charge is low in the cell, how does this affect TCA?
oxaloacetate will replenish TCA instead of being drawn off for gluconeogenesis.
How many moles of ATP will be produced from complete oxidation of one mole of glucose?
30 is the current value...changes every week.
How much more ATP will 1 gram of triglyceride produce than 1 gram of glycogen
6 times as much ATP
What is the fate of glycerol in triglyceride degradation?
It feeds into the glycolytic/gluconeogenic pathway and becomes G3P. It then can become pyruvate or glucose.
What is the fate of fatty acids in triglyceride degradation?
It is linked to Coenzyme A and then to carnitine to shuttle into mitochondria where it undergos Beta oxidation
How does beta oxidation work?
It is a series of 4 reactions that remove 2 carbons at a time from a fatty acid chain to make acetyl CoA
fatty acid oxidation can take place in peroxisomes and mitochondria. What is the difference?
In the peroxisomes there is no electron transport chain and no ATP is generated.
What molecule is used in fatty acid synthesis?
NADPH is needed for reductive biosynthesis to add 2C at a time to a growing chain.
What part of our diet can not be made into glucose?
Fatty acids from triglyceride degradation. They go to acetyl CoA which can't go back to pyruvate
Which enzyme is need to form glucose from glucose 6-phosphate and where is it located?
Glucose 6-phosphatase in the ER membrane of cells in the liver.
What are the 2 main enzymes that are regulated to balance glycolysis and gluconeogenesis?
Phosphofructokinase (glycolysis) and pyruvate kinase (gluconeogenesis)
Which end of glycogen molecule does breakdown occur?
At the non-reducing ends. This is accomplished via activity of glycogen phosphorylase
The activity of glycogen phosphorylase is unique in what way?
It cleaves via phosphorylitic cleavage rather than hydrolytic (requires PLP)
What does a transferase do?
The phosphorylase stops 4 residues from a branch point. Here the tansferase shift a block of 3 residues to another chain.
What does a-1,6-glucosidase do?
It is the debranching enzyme that hydrolyzes the a-1,6-glycosidic bonds.
what does phosphoglucomutase enzyme do?
It converts G6P into G1P
Which enzyme attaches UDP to glucose from G1P?
UDP glucose pyrophosphorylase
What is the role of glycogen synthase?
It transfers a glucose from UDP-glucose to the non-reducing end of growing glycogen chain.
What is the benefit of branching in glycogen molecules?
It increases solubility of glycogen and the rate of synthesis and degradation
How is glycogen breakdown and synthesis regulated?
activation of GPCR via epinephrine activates phosphorylase but inactivates synthase (opposing effects)
What is the fate of amino acids in protein degredation?
alpha amino converted to urea and carbon skeleton converted to acetyl CoA, pyruvate, or TCA intermediate
Where does amino acid degradation take place?
In the liver
Some amino acid skeletons are glucogenic and some are ketogenic. What is the difference?
Ketogenic amino acids are funneled in through acetyl-CoA, which can't be converted to glucose
What is the purpose of the pentose phosphate pathway?
It is the major source of NADPH for reductive biosynthesis and also provides ribose for nucleotide synthesis