Question 1

Which of the following statements concerning arginine is true?

Accepted Answer

A)  Arginine is only marginally an essential amino acid, since it is made in the urea cycle. 
B)  Aspartic acid is the main amino acid precursor for the carbon chain in arginine. 
C)  Lysine could substitute for arginine as a dietary source for arginine. 
D)  Arginine is only essential in adults. 
A)  Arginine is only marginally an essential amino acid, since it is made in the urea cycle. 
B)  Aspartic acid is the main amino acid precursor for the carbon chain in arginine. 
C)  Lysine could substitute for arginine as a dietary source for arginine. 
D)  Arginine is only essential in adults.

Question 2

A molecule synthesized in the mitochondrial matrix and transported to the cytosol for subsequent reaction is

Accepted Answer

A)  arginine 
B)  argininosuccinate 
C)  citrulline 
D)  ornithine 
A)  arginine 
B)  argininosuccinate 
C)  citrulline 
D)  ornithine

Question 3

In the synthesis of purine nucleotides,

Accepted Answer

A)  the ring system is bonded to ribose phosphate only after the complete purine ring is assembled 
B)  the six-membered ring of the purine is assembled first, then the five-membered ring 
C)  there is no requirement for ATP 
D)  the ring system is synthesized onto the ribose phosphate moiety 
A)  the ring system is bonded to ribose phosphate only after the complete purine ring is assembled 
B)  the six-membered ring of the purine is assembled first, then the five-membered ring 
C)  there is no requirement for ATP 
D)  the ring system is synthesized onto the ribose phosphate moiety

Question 4

Which of the following compounds does not serve as an intermediate for the entry of amino acid carbon chains into the major metabolic pathways?

Accepted Answer

A)  Alpha-ketoglutarate. 
B)  Pyruvate. 
C)  Glyceraldehyde. 
D)  Acetyl CoA. 
E)  All of these are entry points for amino acid catabolism. 
A)  Alpha-ketoglutarate. 
B)  Pyruvate. 
C)  Glyceraldehyde. 
D)  Acetyl CoA. 
E)  All of these are entry points for amino acid catabolism.

Question 5

Pyridoxal phosphate is involved in which of the following reactions?

Accepted Answer

A)  transaminations 
B)  decarboxylations 
C)  racemizations 
D)  movement of hydroxymethyl groups 
E)  all of these 
A)  transaminations 
B)  decarboxylations 
C)  racemizations 
D)  movement of hydroxymethyl groups 
E)  all of these

Question 6

Fluorouracil is an effective inhibitor of

Accepted Answer

A)  ribonucleotide reductase 
B)  thymidylate synthase 
C)  xanthine oxidase 
D)  carbamoyl phosphate synthetase 
A)  ribonucleotide reductase 
B)  thymidylate synthase 
C)  xanthine oxidase 
D)  carbamoyl phosphate synthetase

Question 7

Which of the following is not a carrier of one-carbon groups?

Accepted Answer

A)  S-adenosylmethionine 
B)  biotin 
C)  tetrahydrofolate 
D)  thiamine pyrophosphate 
A)  S-adenosylmethionine 
B)  biotin 
C)  tetrahydrofolate 
D)  thiamine pyrophosphate

Question 8

Essential amino acids cannot be synthesized in sufficient quantities within the human body.

Accepted Answer

A) True 
 B)False

Question 9

The urea cycle is linked to the citric acid cycle by

Accepted Answer

A)  arginine 
B)  citrulline 
C)  fumarate 
D)  ornithine 
A)  arginine 
B)  citrulline 
C)  fumarate 
D)  ornithine

Question 10

Which of the following is not an intermediate in the urea cycle?

Accepted Answer

A)  arginine 
B)  citrulline 
C)  ornithine 
D)  lysine 
A)  arginine 
B)  citrulline 
C)  ornithine 
D)  lysine

Question 11

The nitrogen-fixing enzyme system,nitrogenase,is found exclusively in

Accepted Answer

A)  plants 
B)  bacteria 
C)  some viruses 
D)  eukaryotic organisms 
A)  plants 
B)  bacteria 
C)  some viruses 
D)  eukaryotic organisms

Question 12

Ribonucleotide reductase uses which of the following cofactors?

Accepted Answer

A)  biotin 
B)  thiamine pyrophosphate 
C)  tetrahydrofolate 
D)  thioredoxin 
A)  biotin 
B)  thiamine pyrophosphate 
C)  tetrahydrofolate 
D)  thioredoxin

Question 13

Orotic acid is synthesized from

Accepted Answer

A)  glycine and carbamoyl phosphate. 
B)  arginine and carbamoyl phosphate. 
C)  aspartic acid and carbamoyl phosphate. 
D)  aspartic acid and glutamine. 
A)  glycine and carbamoyl phosphate. 
B)  arginine and carbamoyl phosphate. 
C)  aspartic acid and carbamoyl phosphate. 
D)  aspartic acid and glutamine.

Question 14

Many antibiotics,especially for viruses and cancer therapy involve inhibition of folic acid reactions,especially because folic acid is essential for this reaction:

Accepted Answer

A)  Synthesis of many amino acids. 
B)  Conversion of uracil to thymine for DNA synthesis. 
C)  Synthesis of deoxyribose for DNA synthesis. 
D)  None of these reactions explains the reason why inhibitors of folic acid act as antibiotics. 
E)  All of these reactions are reasons why inhibitors of folic acid act as antibiotics. 
A)  Synthesis of many amino acids. 
B)  Conversion of uracil to thymine for DNA synthesis. 
C)  Synthesis of deoxyribose for DNA synthesis. 
D)  None of these reactions explains the reason why inhibitors of folic acid act as antibiotics. 
E)  All of these reactions are reasons why inhibitors of folic acid act as antibiotics.

Question 15

Purine salvage reactions

Accepted Answer

A)  use bases as the substrate 
B)  use nucleosides as the substrate 
C)  produce nucleosides as products 
D)  require the hydrolysis of ATP 
A)  use bases as the substrate 
B)  use nucleosides as the substrate 
C)  produce nucleosides as products 
D)  require the hydrolysis of ATP

Question 16

In nitrogen fixation,the chemical change is

Accepted Answer

A)  NH4+ to NO2- 
B)  NO3- to NH4+ 
C)  N2 to NH4+ or NH3 
D)  NO2- to N2 
A)  NH4+ to NO2- 
B)  NO3- to NH4+ 
C)  N2 to NH4+ or NH3 
D)  NO2- to N2

Question 17

The following two amino acids are key to the transfers of amino groups during breakdown and synthesis of amino acids.

Accepted Answer

A)  GLU and ASP 
B)  GLU and ARG 
C)  GLU and GLN 
D)  ALA and GLN 
E)  ASP and GLN 
A)  GLU and ASP 
B)  GLU and ARG 
C)  GLU and GLN 
D)  ALA and GLN 
E)  ASP and GLN

Question 18

If an amino acid's degradation pathway leads to a-ketoglutarate,is it glucogenic?

Accepted Answer

A)  Yes. 
B)  No. 
C)  Only if the organism has a glyoxylate pathway. 
D)  Only if the organism does not have a glyoxylate pathway. 
A)  Yes. 
B)  No. 
C)  Only if the organism has a glyoxylate pathway. 
D)  Only if the organism does not have a glyoxylate pathway.

Question 19

The ultimate end products of xanthine catabolsim are:

Accepted Answer

A)  two pyrimidines 
B)  urea and glyoxylate 
C)  uric acid 
D)  allantoin 
A)  two pyrimidines 
B)  urea and glyoxylate 
C)  uric acid 
D)  allantoin

Question 20

The conversion of glutamate to glutamine is catalyzed by glutamine synthetase and requires ATP.

Accepted Answer

A) True 
 B)False

Exam 23: The Metabolism of Nitrogen

Which of the following statements concerning arginine is true?

A molecule synthesized in the mitochondrial matrix and transported to the cytosol for subsequent reaction is

In the synthesis of purine nucleotides,

Which of the following compounds does not serve as an intermediate for the entry of amino acid carbon chains into the major metabolic pathways?

Pyridoxal phosphate is involved in which of the following reactions?

Fluorouracil is an effective inhibitor of

Which of the following is not a carrier of one-carbon groups?

Essential amino acids cannot be synthesized in sufficient quantities within the human body.

The urea cycle is linked to the citric acid cycle by

Which of the following is not an intermediate in the urea cycle?

The nitrogen-fixing enzyme system,nitrogenase,is found exclusively in

Ribonucleotide reductase uses which of the following cofactors?

Orotic acid is synthesized from

Many antibiotics,especially for viruses and cancer therapy involve inhibition of folic acid reactions,especially because folic acid is essential for this reaction:

Purine salvage reactions

In nitrogen fixation,the chemical change is

The following two amino acids are key to the transfers of amino groups during breakdown and synthesis of amino acids.

If an amino acid's degradation pathway leads to a-ketoglutarate,is it glucogenic?

The ultimate end products of xanthine catabolsim are:

The conversion of glutamate to glutamine is catalyzed by glutamine synthetase and requires ATP.

Biochemistry and the Organization of Cells

Water: The Solvent for Biochemical Reactions

Amino Acids and Peptides

The Three-Dimensional Structure of Proteins

Protein Purification and Characterization Techniques

The Behavior of Proteins: Enzymes

The Behavior of Proteins: Enzymes, Mechanisms, and Control

Lipids and Proteins Are Associated in Biological Membranes

Nucleic Acids: How Structure Conveys Information

Biosynthesis of Nucleic Acids: Replication

Transcription of the Genetic Code: Biosynthesis of Rna

Protein Synthesis: Translation of the Genetic Message

Nucleic Acid Biotechnology Techniques

Viruses, Cancer, and Immunology

The Importance of Energy Changes and Electron Transfer in Metabolism

Carbohydrates

Glycolysis

Storage Mechanisms and Control in Carbohydrate Metabolism

The Citric Acid Cycle

Electron Transport and Oxidative Phosphorylation

Lipid Metabolism

Photosynthesis

Integration of Metabolism: Cellular Signaling

Filters