Question 1

Show the biosynthetic pathway for the conversion of a citric acid cycle intermediate into proline.Indicate where any cofactors participate.

Accepted Answer

-Ketoglutarate

glutamate

gluta...

Question 2

An intermediate of purine degradation in humans is:

Accepted Answer

A)  glutamate.
B)  NH4+.
C)  succinate.
D)  urea.
E)  uric acid.F) A) and B)
G) B) and E)

Question 3

Give the equations for the two-step reaction sequence catalyzed by glutamine synthetase.

Accepted Answer

(1)Glutamate + ATP

glutamyl ph...

Question 4

Glutathione is a(n) :

Accepted Answer

A)  enzyme essential in the synthesis of glutamate.
B)  isomer of oxidized glutamic acid.
C)  methyl-group donor in many biosynthetic pathways.
D)  product of glutamate and methionine.
E)  tripeptide of glycine,glutamate,and cysteine.F) None of the above
G) A) and E)

Question 5

De novo purine biosynthesis is distinguished from de novo pyrimidine biosynthesis by:

Accepted Answer

A)  condensation of the completed purine ring with ribose phosphate
B)  incorporation of CO2.
C)  inhibition by azaserine (a glutamine analog) .
D)  participation of aspartate.
E)  participation of PRPP (phosphoribosyl pyrophosphate) .F) C) and D)
G) A) and C)

Question 6

Draw the structure of 5'AMP.What is the first "committed" step in the biosynthetic sequence that leads to 5'AMP? How is this step regulated?

Accepted Answer

The structure of AMP is in Fig. 22-36.  ...

Question 7

Precursors for the biosynthesis of the pyrimidine ring system include:

Accepted Answer

A)  carbamoyl phosphate and aspartate.
B)  glutamate,NH3,and CO2.
C)  glycine and succinyl-CoA.
D)  glycine,glutamine,CO2,and aspartate.
E)  inosine and aspartate.F) A) and B)
G) A) and C)

Question 8

Which of the following statements about the fixation of atmospheric nitrogen (N2) into NH3 by living cells is false?

Accepted Answer

A)  It involves the transfer of eight electrons per mol of N2.
B)  It occurs in certain microorganisms,but not in humans.
C)  It requires a source of electrons,normally ferredoxin.
D)  It requires one ATP per mol of N2 fixed.
E)  It requires two key protein components,each containing iron.F) A) and C)
G) B) and E)

Question 9

l-Dopa is an intermediate in the conversion of:

Accepted Answer

A)  phenylalanine to homogentisic acid.
B)  phenylalanine to tyrosine.
C)  tyrosine to epinephrine.
D)  tyrosine to phenylalanine.
E)  tyrosine to phenylpyruvate.F) C) and D)
G) None of the above

Question 10

Why is it necessary to have protein in our (human)diets?

Accepted Answer

Protein provides the 10 essential amino ...

Question 11

Show the two-step reaction catalyzed by tryptophan synthetase.

Accepted Answer

(1)Indole-3-glycerol phosphate...

Question 12

Which of the following is not true about glutamine amidotransferases?

Accepted Answer

A)  These enzymes proceed via a covalent intermediate.
B)  Ammonia is released into a channel.
C)  Glutamate is a product of the reaction.
D)  ATP is needed to activate the glutamine.
E)  A Cys at the active site is critical for the activity of these enzymes.F) B) and C)
G) A) and D)

Question 13

The amino acid that gives rise to the biological messenger NO is:

Accepted Answer

A)  glutamine.
B)  arginine.
C)  proline.
D)  lysine.
E)  histidine.F) A) and B)
G) A) and E)

Question 14

Explain how lack of adenosine deaminase leads to a 100-fold increase in dATP,yet also causes a deficiency in dNTPs required for replication of T-cells and B-cells required for a functioning immune system.

Accepted Answer

Adenosine deaminase is a critical enzyme...

Question 15

Azaserine is a structural analog of glutamine.It is a competitive inhibitor of many enzymes that use glutamine as substrates.Name)three biosynthetic products whose synthesis you would expect to be inhibited by azaserine.Do you think that eating azaserine would be immediately fatal? Why or why not?

Accepted Answer

Azaserine inhibits enzymes involved in t...

Question 16

An amino acid that does not derive its carbon skeleton,at least in part,from  α\alphaα -ketoglutarate is:

Accepted Answer

A)  arginine.
B)  glutamate.
C)  glutamine.
D)  proline.
E)  threonine. F) B) and E)
G) A) and B)

Question 17

Show the reaction catalyzed by thymidylate synthase and explain with a simple diagram how the chemotherapeutic agents fluorouracil and methotrexate inhibit the synthesis of dTMP.

Accepted Answer

The reaction mechanism catalyzed by thym...

Question 18

Which of the following enzymes is not involved in the assimilation of inorganic nitrogen into an organic molecule?

Accepted Answer

A)  Dinitrogenase reductase
B)  Nitrate reductase
C)  Nitrite reductase
D)  Nitrile reductase
E)  DinitrogenaseF) C) and E)
G) D) and E)

Question 19

The ribosyl phosphate moiety needed for the synthesis of orotidylate,inosinate,and guanylate is provided most directly by:

Accepted Answer

A)  5-phosphoribosyl 1-pyrophosphate.
B)  adenosine 5'-phosphate.
C)  guanosine 5'-phosphate.
D)  ribose 5-phosphate.
E)  ribulose 5-phosphate.F) B) and E)
G) All of the above

Question 20

An important intermediate in the biosynthetic pathway to aromatic amino acids is:

Accepted Answer

A)  benzoic acid.
B)  lactate.
C)  orotate.
D)  shikimate.
E)  ( α\alphaα -ketoglutarate.)  F) C) and D)
G) A) and D)

Exam 22: Biosynthesis of Amino Acids, nucleotides, and Related Molecules

An important intermediate in the biosynthetic pathway to aromatic amino acids is:

Correct AnswerverifiedShow Answer

Give the equations for the two-step reaction sequence catalyzed by glutamine synthetase.

Correct Answerverified(1)Glutamate + ATP glutamyl ph...View AnswerShow Answer

Explain how lack of adenosine deaminase leads to a 100-fold increase in dATP,yet also causes a deficiency in dNTPs required for replication of T-cells and B-cells required for a functioning immune system.

Correct AnswerverifiedAdenosine deaminase is a critical enzyme...View AnswerShow Answer

Show the reaction catalyzed by thymidylate synthase and explain with a simple diagram how the chemotherapeutic agents fluorouracil and methotrexate inhibit the synthesis of dTMP.

Correct AnswerverifiedThe reaction mechanism catalyzed by thym...View AnswerShow Answer

Draw the structure of 5'AMP.What is the first "committed" step in the biosynthetic sequence that leads to 5'AMP? How is this step regulated?

Correct AnswerverifiedThe structure of AMP is in Fig. 22-36. ...View AnswerShow Answer

Azaserine is a structural analog of glutamine.It is a competitive inhibitor of many enzymes that use glutamine as substrates.Name)three biosynthetic products whose synthesis you would expect to be inhibited by azaserine.Do you think that eating azaserine would be immediately fatal? Why or why not?

Correct AnswerverifiedAzaserine inhibits enzymes involved in t...View AnswerShow Answer

Precursors for the biosynthesis of the pyrimidine ring system include:

Correct AnswerverifiedShow Answer

Glutathione is a(n) :

Correct AnswerverifiedShow Answer

An intermediate of purine degradation in humans is:

Correct AnswerverifiedShow Answer

De novo purine biosynthesis is distinguished from de novo pyrimidine biosynthesis by:

Correct AnswerverifiedShow Answer

An amino acid that does not derive its carbon skeleton,at least in part,from α\alphaα -ketoglutarate is:

Correct AnswerverifiedShow Answer

Which of the following enzymes is not involved in the assimilation of inorganic nitrogen into an organic molecule?

Correct AnswerverifiedShow Answer

The ribosyl phosphate moiety needed for the synthesis of orotidylate,inosinate,and guanylate is provided most directly by:

Correct AnswerverifiedShow Answer

Which of the following statements about the fixation of atmospheric nitrogen (N2) into NH3 by living cells is false?

Correct AnswerverifiedShow Answer

Show the biosynthetic pathway for the conversion of a citric acid cycle intermediate into proline.Indicate where any cofactors participate.

Correct Answerverified-Ketoglutarate glutamate gluta...View AnswerShow Answer

Why is it necessary to have protein in our (human)diets?

Correct AnswerverifiedProtein provides the 10 essential amino ...View AnswerShow Answer

l-Dopa is an intermediate in the conversion of:

Correct AnswerverifiedShow Answer

Show the two-step reaction catalyzed by tryptophan synthetase.

Correct Answerverified(1)Indole-3-glycerol phosphate...View AnswerShow Answer

Which of the following is not true about glutamine amidotransferases?

Correct AnswerverifiedShow Answer

The amino acid that gives rise to the biological messenger NO is:

Correct AnswerverifiedShow Answer

Correct Answer
verified

Correct Answer
verified
(1)Glutamate + ATP glutamyl ph...
View Answer

Correct Answer
verified
Adenosine deaminase is a critical enzyme...
View Answer

Correct Answer
verified
The reaction mechanism catalyzed by thym...
View Answer

Correct Answer
verified
The structure of AMP is in Fig. 22-36. ...
View Answer

Correct Answer
verified
Azaserine inhibits enzymes involved in t...
View Answer

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

An amino acid that does not derive its carbon skeleton,at least in part,from $\alpha$ -ketoglutarate is:

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Which of the following statements about the fixation of atmospheric nitrogen (N₂) into NH₃ by living cells is false?

Correct Answer
verified

Correct Answer
verified
-Ketoglutarate glutamate gluta...
View Answer

Correct Answer
verified
Protein provides the 10 essential amino ...
View Answer

Correct Answer
verified

Correct Answer
verified
(1)Indole-3-glycerol phosphate...
View Answer

Correct Answer
verified

Correct Answer
verified