Question 1

In the urea cycle,free NH3 is coupled with carboxyphosphate to form

Accepted Answer

A)  ureatic phosphate. 
B)  pyruvate. 
C)  carbamic acid. 
D)  urea. 
E)  None of the answers is correct. 
A)  ureatic phosphate. 
B)  pyruvate. 
C)  carbamic acid. 
D)  urea. 
E)  None of the answers is correct. C

Question 2

What enzyme transfers an $\alpha$-amino group from an amino acid to $\alpha$-ketoglutarate?

Accepted Answer

A)  reductive aminase 
B)  oxidative deaminase 
C)  ketotransferase 
D)  aminotransferase 
E)  None of the answers is correct. 
A)  reductive aminase 
B)  oxidative deaminase 
C)  ketotransferase 
D)  aminotransferase 
E)  None of the answers is correct. D

Question 3

What is the function of the acidic environment in the stomach?

Accepted Answer

The low pH causes the dietary proteins to denature and unfold,making them more susceptible to hydrolytic degradation by pepsin.

Question 4

Describe how the urea cycle is linked to the citric acid cycle.

Accepted Answer

During the urea cycle,aspartate brings i

Question 5

What is the basic strategy by which amino acids are degraded?

Accepted Answer

Amino acids are used for protein synthes

Question 6

What is the significance of the PEST sequence?

Accepted Answer

Some cell-cycle proteins contain unique

Question 7

The urea cycle is linked to gluconeogenesis through the TCA cycle intermediates fumarate and ________________.

Accepted Answer

The answer of The urea cycle is linked to gluconeogenesis...

Question 8

What are some types of enzyme-catalyzed reactions that require pyridoxal phosphate as a coenzyme?

Accepted Answer

The reactions include transami

Question 9

In the first step of the urea cycle,CO2 and NH4+ are converted into __________________.

Accepted Answer

Question 10

Write the net equation of the urea cycle and indicate whether energy is produced or consumed by the cycle.

Accepted Answer

CO₂ + NH₄⁺ + 3 ATP + Asp + 2 H₂O →

Question 11

Why are four or more chains of ubiquitin particularly effective as a signal for degradation?

Accepted Answer

When several ubiquitin chains are attach

Question 12

In the transaminase reaction,pyridoxal phosphate is converted into __________________ when the first amino acid is converted into an $\alpha$ keto acid.

Accepted Answer

pyridoxami

Question 13

Which of the following is the primary proteolytic enzyme of the stomach?

Accepted Answer

A)  trypsin 
B)  chymotrypsin 
C)  elastase 
D)  carboxypeptidase A 
E)  pepsin 
A)  trypsin 
B)  chymotrypsin 
C)  elastase 
D)  carboxypeptidase A 
E)  pepsin

Question 14

Which amino acids can be directly deaminated to produce NH4+?

Accepted Answer

A)  serine and threonine 
B)  serine, asparagine, and threonine 
C)  proline and threonine 
D)  proline and valine 
E)  None of the answers is correct. 
A)  serine and threonine 
B)  serine, asparagine, and threonine 
C)  proline and threonine 
D)  proline and valine 
E)  None of the answers is correct.

Question 15

What cofactor is required by phenylalanine hydroxylase?

Accepted Answer

A)  flavin mononucleotide 
B)  pyridoxal phosphate 
C)  dihydrofolate 
D)  nicotinamide adenine dinucleotide 
E)  tetrahydrobiopterin 
A)  flavin mononucleotide 
B)  pyridoxal phosphate 
C)  dihydrofolate 
D)  nicotinamide adenine dinucleotide 
E)  tetrahydrobiopterin

Question 16

Four of the five enzymes in the urea cycle are evolutionarily related to enzymes found in

Accepted Answer

A)  glucose transport. 
B)  electron transport chain. 
C)  nucleotide biosynthesis. 
D)  ubiquitination. 
E)  None of the answers is correct. 
A)  glucose transport. 
B)  electron transport chain. 
C)  nucleotide biosynthesis. 
D)  ubiquitination. 
E)  None of the answers is correct.

Question 17

Describe the glucose-alanine cycle and its significance in amino acid metabolism.

Accepted Answer

During prolonged exercise and fasting,mu

Question 18

The eukaryotic system for ubiquitination appears to have evolved from what prokaryotic precursor?

Accepted Answer

A)  A system for protein degradation and turnover 
B)  A system for protein phosphorylation 
C)  A system for thiamine biosynthesis 
D)  A system for nucleotide degradation 
E)  None of the answers is correct. 
A)  A system for protein degradation and turnover 
B)  A system for protein phosphorylation 
C)  A system for thiamine biosynthesis 
D)  A system for nucleotide degradation 
E)  None of the answers is correct.

Question 19

Ketogenic amino acids are degraded to which of the following metabolites?

Accepted Answer

A)  pyruvate 
B)  acetoacetate 
C)  oxaloacetate 
D)  $\alpha$-ketoglutarate 
E)  All of the answers are correct. 
A)  pyruvate 
B)  acetoacetate 
C)  oxaloacetate 
D)  $\alpha$-ketoglutarate 
E)  All of the answers are correct.

Question 20

Which amino acid is a metabolite in the urea cycle but is not used as a building block of proteins?

Accepted Answer

A)  ornithine 
B)  aspartate 
C)  glutamate 
D)  lysine 
E)  arginine 
A)  ornithine 
B)  aspartate 
C)  glutamate 
D)  lysine 
E)  arginine

Exam 23: Protein Turnover and Amino Acid Catabolism

In the urea cycle,free NH3 is coupled with carboxyphosphate to form

What enzyme transfers an α\alphaα -amino group from an amino acid to α\alphaα -ketoglutarate?

What is the function of the acidic environment in the stomach?

Describe how the urea cycle is linked to the citric acid cycle.

What is the basic strategy by which amino acids are degraded?

What is the significance of the PEST sequence?

The urea cycle is linked to gluconeogenesis through the TCA cycle intermediates fumarate and ________________.

What are some types of enzyme-catalyzed reactions that require pyridoxal phosphate as a coenzyme?

In the first step of the urea cycle,CO2 and NH4+ are converted into __________________.

Write the net equation of the urea cycle and indicate whether energy is produced or consumed by the cycle.

Why are four or more chains of ubiquitin particularly effective as a signal for degradation?

In the transaminase reaction,pyridoxal phosphate is converted into __________________ when the first amino acid is converted into an α\alphaα keto acid.

Which of the following is the primary proteolytic enzyme of the stomach?

Which amino acids can be directly deaminated to produce NH4+?

What cofactor is required by phenylalanine hydroxylase?

Four of the five enzymes in the urea cycle are evolutionarily related to enzymes found in

Describe the glucose-alanine cycle and its significance in amino acid metabolism.

The eukaryotic system for ubiquitination appears to have evolved from what prokaryotic precursor?

Ketogenic amino acids are degraded to which of the following metabolites?

Which amino acid is a metabolite in the urea cycle but is not used as a building block of proteins?

Biochemistry: An Evolving Science

Protein Composition and Structure

Exploring Proteins and Proteomes

DNA, RNA, and the Flow of Genetic Information

Exploring Genes and Genomes

Exploring Evolution and Bioinformatics

Hemoglobin: a Portrait of a Protein in Action

Enzymes: Basic Concepts and Kinetics

Catalytic Strategies

Regulatory Strategies

Carbohydrates

Lipids and Cell Membranes

Membrane Channels and Pumps

Signal-Transduction Pathways

Metabolism: Basic Concepts and Design

Glycolysis and Gluconeogenesis

The Citric Acid Cycle

Oxidative Phosphorylation

The Light Reactions of Photosynthesis

The Calvin Cycle and the Pentose Phosphate Pathway

Glycogen Metabolism

Fatty Acid Metabolism

The Biosynthesis of Amino Acids

Nucleotide Biosynthesis

Biosynthesis of Membrane Lipids and Steroids

The Integration of Metabolism

DNA Replication, repair, and Recombination

RNA Synthesis and Processing

Protein Synthesis

The Control of Gene Expression in Prokaryotes

The Control of Gene Expression in Eukaryotes

Sensory Systems

The Immune System

Molecular Motors

Drug Development

Filters

In the urea cycle,free NH₃ is coupled with carboxyphosphate to form

What enzyme transfers an $\alpha$ -amino group from an amino acid to $\alpha$ -ketoglutarate?

In the first step of the urea cycle,CO₂ and NH₄⁺ are converted into __________________.

In the transaminase reaction,pyridoxal phosphate is converted into __________________ when the first amino acid is converted into an $\alpha$ keto acid.

Which amino acids can be directly deaminated to produce NH₄⁺?