Chapter 21 - Amino Acid Metabolism Practice Quiz PDF

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This is a practice quiz for chapter 21 of biochem II. This is similar to the in class quiz. It can also serve as a study guide for the test. It also helps with the assignments. Contains questions and answers....

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1/6 Biochemistry II Chapter 21: Amino Acid Metabolism Textbook: Fundamentals of Biochemistry: Life at the Molecular Level, 5th Edition. Donald Voet; Judith G. Voet Practice Quiz 1. Match each of the following: 1. A class of lipoproteins that transports endogenous triacylglycerols and cholesterol from the liver to the tissues. 2. Cell-surface membrane glycoproteins that bind specifically to apoB-100. 3. A single-copy protein that is wrapped around the outer surface of LDL. 4. A class of lipoproteins that transports dietary triacylglycerols and cholesterol from the intestines to the tissues. 5. A class of lipoproteins that transports endogenous cholesterol from the tissues to the liver. 6. The protein components of lipoproteins. Chylomicrons

4

Low density lipoproteins (LDL)

1

High density lipoproteins (HDL)

5

Apolipoproteins

6

ApoB-100

3

LDL receptors

2

2. Cells obtain exogenous cholesterol mainly through receptor-mediated endocytosis.

2/6 3. Under conditions of nutritional deprivation, cells increase their rate of protein degradation. 4. Lysosomal enzymes are mostly inactive at cytosolic pH's. 5. Ubiquitin is a small protein that marks other proteins for degradation. 6. True or false. A protective mechanism switches lysosomal degradation of proteins from non-selective to selective during starvation. True. 7. True or false. In both prokaryotes and eukaryotes, proteins are marked for ATP-dependent degradation with ubiquitin. False. NOTE: Prokaryotes do not have ubiquitin. 8. True or false. Proteins that are rich in PEST sequences have relatively short half-lives. True. NOTE: PEST proteins are rapidly degraded. 9. True or false. Lipoproteins are globular particles containing lipids covalently attached to proteins. False. NOTE: The lipids and proteins are not covalently attached. 10. The transfer of an amino group from an amino acid to an α-keto acid to form the α-keto acid of the original amino acid and a new amino acid is called transamination. 11. Oxidative deamination of glutamate is catalyzed by glutamate dehydrogenase. 12. True or false. The oxidative deamination of glutamate produces ammonia and oxaloacetate. False. NOTE: It produces ammonia and α-ketoglutarate. 13. True or false. Aminotransferases differ in their specificity for amino acid substrates. True.

3/6 14. Match each of the following: 1. Form of nitrogen excretion in mammals. 2. Form of nitrogen excretion in fish 3. Form of nitrogen excretion in birds. 4. Immediate precursor of urea. 5. Activator of the enzyme that catalyzes the first committed step in the urea cycle. Ammonia

2

N-acetylglutamate

5

Urea

1

Arginine

4

Uric acid

3

15. The first nitrogen atom in urea comes from ammonia. 16. Citrulline formation via ornithine transcarbamoylase occurs in the mitochondrion. 17. Argininosuccinate formation occurs in the cytosol. 18. True or false. Ornithine diffuses into the mitochondrion where it participates in the urea cycle. False. NOTE: Ornithine requires a transport system to enter the mitochondrion. 19. True or false. Two reactions that result in the formation of argininosuccinate are the same as two reactions of the citric acid cycle except that they occur in the cytosol. True.

4/6 20. Match each of the following: 1. Asparagine is degraded to this compound. 2. Serine is degraded to this compound. 3. Glucogenic degradation of phenylalanine leads to this compound. 4. Valine is degraded to this compound. 5. Ketogenic degradation of phenylalanine leads to this compound. 6. Ketogenic degradation of isoleucine leads to this compound. 7. Glutamine is degraded to this compound. Acetyl-CoA

6

Succinyl-CoA

4

Fumarate

3

Oxaloacetate

1

Acetoacetate

5

α-Ketoglutarate

7

Pyruvate

2

21. Amino acids that are broken down to acetyl-CoA or acetoacetate can then be converted to fatty acids or ketone bodies. 22. The important cofactor, THF, acts as a one-carbon carrier. 23. Phenylalanine is converted to tyrosine, another amino acid, as the first step in its degradation. 24. True or false. During degradation, glycine is first converted to serine by serine dehydratase. False. NOTE: Glycine is first converted to serine by serine hydroxymethyl transferase.

5/6 25. True or false. Conversion of glutamine to glutamate requires only glutaminase. True. 26. True or false. Methionine is converted to SAM by a reaction with ATP. True. 27. Match each of the following: 1. Utilizes glutamine as its amino group donor and cleaves ATP to AMP + PPi. 2. In bacteria, it has nine allosteric feed-back inhibitor binding sites. 3. The biosynthesis of lysine, methionine and threonine all begin with phosphorylation catalyzed by this enzyme. 4. Common intermediate in aromatic amino acid synthesis. 5. The compound joined with serine to yield tryptophan. 6. Five of histidine's carbon atoms are derived from this compound. Indole

5

Glutamine synthetase

2

PRPP (5-phosphoryl-α-pyrophosphate)

6

Aspartokinase

3

Asparagine synthetase

1

Chorismate

4

28. Amino acids that must be obtained from the diet in mammals are termed essential amino acids. 29. The activity of E. coli glutamine synthatase decreases with the degree of adenylylation. 30. In animals, serine is derived from 3-phosphoglycerate. 31. True or false. Channeling may be particularly important for indole since this nonpolar molecule can diffuse across membranes. True.

6/6 32. True or false. Mammals synthesize tyrosine directly from prephenate. False. NOTE: Many microorganisms can do this, but not mammals. 33. Match each of the following: 1. Two of these molecules combine to make porphobilinogen. 2. Heme stimulates protein synthesis here. 3. A product of heme degradation. 4. A major inhibitory neurotransmitter of the brain. 5. Derivative of tyrosine. γ-Aminobutyric acid (GABA)

4

δ-Aminolevulinic acid (ALA)

1

Bilirubin

3

Dopamine

5

Reticulocytes

2

34. All of the C and N atoms of heme can be derived from acetate and glycine. 35. ALA is synthesized in the mitochondrion. 36. Porphyrias is the result of a genetic defect in heme biosynthesis. 37. True or false. NO is used to kill invading bacteria by leukocytes (white blood cells). True. 38. True or false. Dopamine deficiency is associated with Parkinson's disease. True. 39. Nitrogen fixation is catalyzed by nitrogenase. 40. The bacteria that can fix nitrogen are called diazotrophs. 41. True or false. Slash and burn agricultural techniques deplete the soil of nitrogen. False. NOTE: These techniques are used to add available nitrogen to the soil....