Question 1

Pyridoxal phosphate forms a Schiff base with amino groups in transaminase reactions.

Accepted Answer

A) True 
 B)False

Question 2

Humans produce these as the major nitrogen waste products.

Accepted Answer

A)  Ammonia. 
B)  Urea. 
C)  Uric Acid. 
D)  Both Urea and Uric Acid. 
E)  All three of these are used to dispose of nitrogen wastes by humans. 
A)  Ammonia. 
B)  Urea. 
C)  Uric Acid. 
D)  Both Urea and Uric Acid. 
E)  All three of these are used to dispose of nitrogen wastes by humans.

Question 3

The carbon skeletons of many amino acids can be used to replenish the intermediates of the citric acid cycle.

Accepted Answer

A) True 
 B)False

Question 4

Kwashiorkor is a malnutrition disease in which high quality proteins are lacking, even if enough calories are available for survival.

Accepted Answer

A) True 
 B)False

Question 5

The conversion of uracil to thymine requires

Accepted Answer

A)  a one-carbon transfer with S -adenosylmethionine as the donor 
B)  a one-carbon transfer with tetrahydrofolate as the donor 
C)  a one-carbon transfer with biotin as the donor 
D)  a one-carbon transfer with oxaloacetate as the donor 
A)  a one-carbon transfer with S -adenosylmethionine as the donor 
B)  a one-carbon transfer with tetrahydrofolate as the donor 
C)  a one-carbon transfer with biotin as the donor 
D)  a one-carbon transfer with oxaloacetate as the donor

Question 6

​ In the nitrogenase complex, several types of subunits are arranged in _____.

Accepted Answer

A)  octamers 
B)  hexamers 
C)  pentamers 
D)  tetramers 
A)  octamers 
B)  hexamers 
C)  pentamers 
D)  tetramers

Question 7

How is cancer chemotherapy related to purine biosyntheis?

Accepted Answer

A)  rapidly dividing cells require more purine biosynthesis and some chemotherapy drugs inhibit a key enzyme in purine biosynthesis 
B)  aminopterin is a good chemotherapy drug because it inhibits aspartate transcarbamoylase 
C)  cancer cells lack folic acid, and chemotherapy drugs like sulfanamide act by overproducing folic acid, which is then poisonous to the cancer cells 
D)  none of these 
A)  rapidly dividing cells require more purine biosynthesis and some chemotherapy drugs inhibit a key enzyme in purine biosynthesis 
B)  aminopterin is a good chemotherapy drug because it inhibits aspartate transcarbamoylase 
C)  cancer cells lack folic acid, and chemotherapy drugs like sulfanamide act by overproducing folic acid, which is then poisonous to the cancer cells 
D)  none of these

Question 8

​ Explain the importance of the feedback inhibition mechanism in nitrogen metabolism.

Accepted Answer

The biosynthesis pathways that produce a

Question 9

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 
E)  none of these 
A)  use bases as the substrate 
B)  use nucleosides as the substrate 
C)  produce nucleosides as products 
D)  require the hydrolysis of ATP 
E)  none of these

Question 10

Lesch-Nyhan syndrome involves a genetic error in the pyrimidine salvage pathways.

Accepted Answer

A) True 
 B)False

Question 11

The energy costs for synthesizing the bases for RNA and DNA is so high that salvage pathways have been developed to recycle existing bases and nucleotides.

Accepted Answer

A) True 
 B)False

Question 12

Glutamine synthetase is subject to feedback inhibition by which of the following chemicals?

Accepted Answer

A)  histidine 
B)  carbamoyl phosphate 
C)  cytidine triphosphate (CTP) 
D)  All of these 
A)  histidine 
B)  carbamoyl phosphate 
C)  cytidine triphosphate (CTP) 
D)  All of these

Question 13

High protein foods are not advisable for the long distance runner during a race because they increase the need for water and for urination.

Accepted Answer

A) True 
 B)False

Question 14

Which of the following is not a characteristic of pyridoxal in its active form?

Accepted Answer

A)  It is covalently bonded to its enzyme. 
B)  It requires being attached to a phosphate group. 
C)  It bonds to an amine group through by means of the phosphate group. 
D)  It has a particularly reactive carbonyl group. 
A)  It is covalently bonded to its enzyme. 
B)  It requires being attached to a phosphate group. 
C)  It bonds to an amine group through by means of the phosphate group. 
D)  It has a particularly reactive carbonyl group.

Question 15

A coenzyme frequently encountered in transamination reactions is

Accepted Answer

A)  tetrahydrofolate. 
B)  pyridoxal phosphate. 
C)  thiamine pyrophosphate. 
D)  biotin. 
A)  tetrahydrofolate. 
B)  pyridoxal phosphate. 
C)  thiamine pyrophosphate. 
D)  biotin.

Question 16

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 17

While the reduction of nitrogen to ammonia in plants follows the same net chemical reaction, the source of electrons for the process varies from plant to plant.

Accepted Answer

A) True 
 B)False

Question 18

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 19

Which best describes the synthesis of purine nucleotides?

Accepted Answer

A)  The basic ring structure, inosine, is synthesized first and then linked to ribose. This is then modified to produce either GMP or AMP. 
B)  The basic ring structure, orotate, is synthesized stepwise on ribose. This is then modified to produce either GMP or AMP. 
C)  The basic ring structure, inosine, is synthesized stepwise on ribose. This is then modified to produce either GMP or AMP. 
D)  The basic ring structure, orotate, is synthesized first and then linked to ribose. This is then modified to produce either UMP or CMP. 
A)  The basic ring structure, inosine, is synthesized first and then linked to ribose. This is then modified to produce either GMP or AMP. 
B)  The basic ring structure, orotate, is synthesized stepwise on ribose. This is then modified to produce either GMP or AMP. 
C)  The basic ring structure, inosine, is synthesized stepwise on ribose. This is then modified to produce either GMP or AMP. 
D)  The basic ring structure, orotate, is synthesized first and then linked to ribose. This is then modified to produce either UMP or CMP.

Question 20

The synthesis of amino acids occurs in about 5 or 6 related families of amino acids.

Accepted Answer

A) True 
 B)False

Exam 23: The Metabolism of Nitrogen

Pyridoxal phosphate forms a Schiff base with amino groups in transaminase reactions.

Humans produce these as the major nitrogen waste products.

The carbon skeletons of many amino acids can be used to replenish the intermediates of the citric acid cycle.

Kwashiorkor is a malnutrition disease in which high quality proteins are lacking, even if enough calories are available for survival.

The conversion of uracil to thymine requires

​ In the nitrogenase complex, several types of subunits are arranged in _____.

How is cancer chemotherapy related to purine biosyntheis?

​ Explain the importance of the feedback inhibition mechanism in nitrogen metabolism.

Purine salvage reactions

Lesch-Nyhan syndrome involves a genetic error in the pyrimidine salvage pathways.

The energy costs for synthesizing the bases for RNA and DNA is so high that salvage pathways have been developed to recycle existing bases and nucleotides.

Glutamine synthetase is subject to feedback inhibition by which of the following chemicals?

High protein foods are not advisable for the long distance runner during a race because they increase the need for water and for urination.

Which of the following is not a characteristic of pyridoxal in its active form?

A coenzyme frequently encountered in transamination reactions is

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

While the reduction of nitrogen to ammonia in plants follows the same net chemical reaction, the source of electrons for the process varies from plant to plant.

In the synthesis of purine nucleotides,

Which best describes the synthesis of purine nucleotides?

The synthesis of amino acids occurs in about 5 or 6 related families of amino acids.

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 the 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

In the nitrogenase complex, several types of subunits are arranged in _____.

Explain the importance of the feedback inhibition mechanism in nitrogen metabolism.