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