Deck 25: Protein and Amino Acid Metabolism

Question 1

Which is the correct order for the steps in digestion and absorption of proteins?
I.hydrolysis by pancreatic lipases
II.denaturation by stomach acid
III.hydrolysis by pepsin
IV.active transport into the bloodstream

A)I,II,III,IV
B)IV,II,III,I
C)II,I,III,IV
D)II,III,I,IV
E)III,II,IV,I

Answer 1

II,III,I,IV

Question 2

Which pH range is the one where the enzymes trypsin and chymotrypsin are most active?

A)1-2
B)3-4
C)5-6
D)7-8
E)9-10

Answer 2

7-8

Question 3

Which statement best summarizes the digestion of proteins?

A)Amine groups are removed from all amino acids.
B)All peptide linkages are hydrolyzed to produce a mixture of amino acids.
C)Proteins are denatured by stomach acid.
D)Amino acids are combined to produce proteins or enzymes.
E)none of the above

Answer 3

All peptide linkages are hydrolyzed to produce a mixture of amino acids.

Question 4

The enzyme that removes an amine group from an amino acid and moves it to α-ketoglutarate is classified as a

A)ligase.
B)phosphatase.
C)transaminase.
D)dehydrogenase.
E)kinase.

Question 5

Since the formation of ammonia is toxic to cells,the amino nitrogen from protein catabolism

A)can be excreted in the form of urea.
B)can be used in the synthesis of nitrogen containing hormones.
C)can be used in the synthesis of nucleic acids.
D)all of the above
E)none of the above

Question 6

The common features of catabolism of all amino acids include

A)removal of the amine group and conversion of the carbon skeleton to intermediates which can enter the citric acid cycle.
B)hydrolysis of peptide linkages and production of CO₂ as waste.
C)hydrolysis of peptide linkages and production of urea as waste.
D)diversion of the carbon skeletons into gluconeogenesis.
E)diversion of the carbon skeletons into ketogenesis.

Question 7

During catabolism of amino acids the carbon based intermediates can

A)enter storage as triglycerides.
B)enter storage as glycogen.
C)be converted into ketone bodies.
D)all of the above
E)none of the above

Question 8

One of the most important functions of amino acids is for the synthesis of

A)glucose.
B)pyruvate for energy.
C)body proteins.
D)purines and pyrimidines.

Question 9

Two key amino acids in the transfer or catabolism of amino groups are

A)aspartate and phenylalanine.
B)aspartate and tyrosine.
C)aspartate and glutamate.
D)glutamate and asparagine.
E)alanine and valine.

Question 10

Which of the following enzymes is involved in protein digestion in the stomach?

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

Question 11

Which of the following enzymes is not involved in the digestion of proteins?

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

Question 12

When α-ketoglutarate accepts an amine group,it is converted to

A)glutamate.
B)pyruvate.
C)acetyl.
D)transaminase.
E)urea.

Question 13

Define the terms

A)amino acid pool and
B)turnover for a protein

Question 14

When an amino group is transferred to α-ketoglutarate,one product is always

A)glycine.
B)glutamate.
C)aspartate.
D)alanine.
E)leucine.

Question 15

In the general process for amino acid catabolism,one of the steps involves

A)the use of the removed amino group in the synthesis of new nitrogen compounds.
B)removal of the amino group.
C)passage of the nitrogen into the urea cycle.
D)all of these
E)none of these

Question 16

The amino acid pool is the collection of

A)all amino acids available from the diet.
B)amino acids produced from breakdown of proteins and available for reuse.
C)essential amino acids available from the diet or from breakdown of other proteins.
D)all free amino acids in the body.
E)all amino acids in the body,whether free or part of proteins.

Question 17

When the amino group of glutamate is replaced with a carbonyl group,the process is called

A)hydrolysis.
B)oxidative deamination.
C)reductive deamination.
D)oxidative decarboxylation.
E)phosphorylation.

Question 18

When the amino acid alanine is deaminated,it is converted to

A)glutamate.
B)acetate.
C)pyruvate.
D)oxaloacetate.
E)urea.

Question 19

α-ketoglutarate is converted to glutamate by

A)loss of a carbonyl group.
B)loss of a carboxyl group.
C)accepting an acetyl group.
D)loss of an amide linkage.
E)accepting an amine group.

Question 20

What percentage of a healthy adult's energy need is met by metabolism of protein?

A)less than 5
B)10-20
C)35-45
D)65-75
E)more than 90

Question 21

Which citric acid cycle intermediate is formed in the urea cycle?

A)oxaloacetate
B)succinate
C)fumarate
D)isocitrate
E)malate

Question 22

The first step in amino acid catabolism is

A)transamination.
B)decarboxylation.
C)oxidation.
D)esterification.
E)tautomerization.

Question 23

Gout is a disease state that results from the precipitation of compounds containing ________ in joints in the hands and feet.

A)urate
B)urea
C)glutamate
D)oxalate
E)acetate

Question 24

Ketogenic amino acids cannot be converted into which of the following?

A)fatty acids
B)glucose
C)ketone bodies
D)acetyl CoA
E)They can be converted into all of the above.

Question 25

All of the following chemicals are part of the urea cycle except

A)carbamoyl phosphate.
B)citrulline.
C)arginine.
D)fumarate.
E)acetyl-CoA.

Question 26

When glutamate acts as the source of an amino group,the enzyme involved is a

A)transferase.
B)lipase.
C)pepsin.
D)synthetase.
E)dehydrogenase.

Question 27

The process by which an amino group of one amino acid is exchanged with the keto group of an α-ketoacid is called a

A)oxidative deamination.
B)reductive deamination.
C)transamination.
D)hydrolysis.
E)transfer reaction.

Question 28

The urea cycle is part of the metabolic breakdown of

A)amino acids.
B)pyrimidines.
C)purines.
D)lipids.
E)carbohydrates.

Question 29

One of the intermediates formed in the urea cycle is the protein amino acid

A)glutamate.
B)ornithine.
C)aspartate.
D)arginine.
E)citrulline.

Question 30

Which of the following is the usual reactant in the urea cycle?

A)NH₄⁺
B)glutamate
C)pyruvate
D)carbamoyl phosphate
E)CO₂

Question 31

What is the structural formula of urea?

A)

B) NH₄⁺
C)

D)

E)

Question 32

The reaction of pyruvate with glutamate is the main synthetic route for the formation of

A)aspartate.
B)alanine.
C)phenylalanine.
D)glycine.
E)α-ketoglutarate.

Question 33

If nitrogen is to be excreted from the body,it is converted to which chemical?

A)ammonia
B)arginine
C)glycine
D)α-ketoglutarate
E)urea

Question 34

The urea cycle is ________ because it ________.

A)exergonic;costs 3 ATP
B)exergonic;releases 3 ATP
C)endergonic;costs 3 ATP
D)endergonic;releases 3 ATP
E)neither exergonic nor endergonic;consumes 3 ATP in an early step and releases 3 ATP in a later step

Question 35

Glucogenic amino acids can be converted into which of the following?

A)glucose
B)fatty acids
C)acetyl CoA
D)ketone bodies
E)They can be converted into all of the above.

Question 36

The process of oxidative deamination of an amino acid produces which of the following?

A)urea
B)CO₂ and H₂O
C)NH₄⁺
D)aspartate
E)glutamate

Question 37

The structural formula of glutamate is

A)

.
B)NH₄⁺.
C)

.
D)

.
E)

.

Question 38

The conversion of nitrogen derivatives to urea takes place in the

A)blood.
B)kidneys.
C)liver.
D)brain.
E)intestines.

Question 39

α-ketoacids are produced as a result of a transamination reaction with ________ acting as the donor molecule.

A)glutamate
B)aspartate
C)urea
D)ornithine
E)oxaloacetate

Question 40

Which of the following types of compounds do not require nitrogen for their biosynthesis?

A)purines
B)pyrimidines
C)neurotransmitters
D)urea
E)All of these require nitrogen.

Question 41

Match the following.
transamination

A)an amino acid whose carbon skeleton can be converted to a citric acid cycle intermediate,that ultimately becomes glucose
B)an amino acid whose carbon skeleton can be converted to a citric acid cycle intermediate that later becomes a ketone body or a fatty acid
C)the biochemical pathway that converts nitrogen and its derivatives to a less toxic form for excretion
D)an amino acid which can be synthesized by the human body as needed
E)the collection of all the free amino acids in the body
F)the transfer of an amine group from an amino acid to an α-keto acid
G)an amino acid that must be obtained in the diet because humans do not have the appropriate anabolic pathways for its synthesis

Question 42

Complementary sources of protein are

A)single foods that contain all of the essential amino acids.
B)single foods that contain all of the nonessential amino acids.
C)single foods that contain none of the essential amino acids.
D)single foods that contain none of the nonessential amino acids.
E)combinations of foods that provide all of the amino acids,both essential and nonessential.

Question 43

The amino acid ________ is important in the formation of collagen and elastin.

A)phenylalanine
B)methionine
C)isoleucine
D)threonine
E)histidine

Question 44

The source of nitrogen for the synthesis of nonessential amino acids is

A)glutamate.
B)acetate.
C)pyruvate.
D)oxaloacetate.
E)urea.

Question 45

Match the following.
urea cycle

A)an amino acid whose carbon skeleton can be converted to a citric acid cycle intermediate,that ultimately becomes glucose
B)an amino acid whose carbon skeleton can be converted to a citric acid cycle intermediate that later becomes a ketone body or a fatty acid
C)the biochemical pathway that converts nitrogen and its derivatives to a less toxic form for excretion
D)an amino acid which can be synthesized by the human body as needed
E)the collection of all the free amino acids in the body
F)the transfer of an amine group from an amino acid to an α-keto acid
G)an amino acid that must be obtained in the diet because humans do not have the appropriate anabolic pathways for its synthesis

Question 46

Match the following.
glucogenic amino acid

A)an amino acid whose carbon skeleton can be converted to a citric acid cycle intermediate,that ultimately becomes glucose
B)an amino acid whose carbon skeleton can be converted to a citric acid cycle intermediate that later becomes a ketone body or a fatty acid
C)the biochemical pathway that converts nitrogen and its derivatives to a less toxic form for excretion
D)an amino acid which can be synthesized by the human body as needed
E)the collection of all the free amino acids in the body
F)the transfer of an amine group from an amino acid to an α-keto acid
G)an amino acid that must be obtained in the diet because humans do not have the appropriate anabolic pathways for its synthesis

Question 47

Which of the following amino acids is essential in growing children and in the repair of tissue?

A)arginine
B)histidine
C)glutamine
D)lysine
E)valine

Question 48

Which of the following processes is important when new amino acids are produced in the body?

A)deamination
B)transamination
C)urea cycle
D)phosphorylation

Question 49

An essential amino acid is one that

A)is required for the synthesis of all proteins.
B)must be obtained in the diet because the human body cannot synthesize it.
C)can safely be omitted from the diet because the human body can produce it in unlimited amounts.
D)must be provided in the diet for individuals with specific hereditary enzyme deficiencies.
E)has a relatively simple carbon skeleton.

Question 50

Amino acids that can be synthesized in the body are called ________ amino acids.

A)essential
B)glycogenic
C)ketogenic
D)nonessential

Question 51

All of the carbon backbones from amino acids end up as intermediates in the

A)citric acid cycle.
B)urea cycle.
C)β-oxidation sequence.
D)both A and C
E)none of the above

Question 52

Each of the following metabolic intermediates is a precursor to one or more amino acids except

A)fumarate.
B)α-ketoglutarate.
C)oxaloacetate.
D)3-phosphoglycerate.
E)pyruvate.

Question 53

Match the following.
amino acid pool

A)an amino acid whose carbon skeleton can be converted to a citric acid cycle intermediate,that ultimately becomes glucose
B)an amino acid whose carbon skeleton can be converted to a citric acid cycle intermediate that later becomes a ketone body or a fatty acid
C)the biochemical pathway that converts nitrogen and its derivatives to a less toxic form for excretion
D)an amino acid which can be synthesized by the human body as needed
E)the collection of all the free amino acids in the body
F)the transfer of an amine group from an amino acid to an α-keto acid
G)an amino acid that must be obtained in the diet because humans do not have the appropriate anabolic pathways for its synthesis

Question 54

Match the following.
essential amino acid

A)an amino acid whose carbon skeleton can be converted to a citric acid cycle intermediate,that ultimately becomes glucose
B)an amino acid whose carbon skeleton can be converted to a citric acid cycle intermediate that later becomes a ketone body or a fatty acid
C)the biochemical pathway that converts nitrogen and its derivatives to a less toxic form for excretion
D)an amino acid which can be synthesized by the human body as needed
E)the collection of all the free amino acids in the body
F)the transfer of an amine group from an amino acid to an α-keto acid
G)an amino acid that must be obtained in the diet because humans do not have the appropriate anabolic pathways for its synthesis

Question 55

The amino acid ________ plays a role in the absorption of calcium and formation of collagen for bones.

A)phenylalanine
B)methionine
C)lysine
D)isoleucine
E)histidine

Question 56

Match the following.
ketogenic amino acid

A)an amino acid whose carbon skeleton can be converted to a citric acid cycle intermediate,that ultimately becomes glucose
B)an amino acid whose carbon skeleton can be converted to a citric acid cycle intermediate that later becomes a ketone body or a fatty acid
C)the biochemical pathway that converts nitrogen and its derivatives to a less toxic form for excretion
D)an amino acid which can be synthesized by the human body as needed
E)the collection of all the free amino acids in the body
F)the transfer of an amine group from an amino acid to an α-keto acid
G)an amino acid that must be obtained in the diet because humans do not have the appropriate anabolic pathways for its synthesis

Question 57

Which of the following common metabolites may be precursors for the synthesis of nonessential amino acids?

A)pyruvate
B)oxaloacetate
C)3-phosphoglycerate
D)α-ketoglutarate
E)All of these may be used.

Question 58

In the anabolism of amino acids,________ is the source of the amine group.

A)aspartate
B)urea
C)glutamate
D)arginine
E)phenylalanine

Question 59

Explain the difference between ketogenic and glucogenic amino acids.Identify the amino acids in each category.

Question 60

PKU,phenylketonuria,is caused by a defect in the enzyme that converts

A)alanine to serine.
B)phenylalanine to tyrosine.
C)tryptophan to tyrosine.
D)alanine to phenylalanine.

Question 61

Match the following.
nonessential amino acid

A)an amino acid whose carbon skeleton can be converted to a citric acid cycle intermediate,that ultimately becomes glucose
B)an amino acid whose carbon skeleton can be converted to a citric acid cycle intermediate that later becomes a ketone body or a fatty acid
C)the biochemical pathway that converts nitrogen and its derivatives to a less toxic form for excretion
D)an amino acid which can be synthesized by the human body as needed
E)the collection of all the free amino acids in the body
F)the transfer of an amine group from an amino acid to an α-keto acid
G)an amino acid that must be obtained in the diet because humans do not have the appropriate anabolic pathways for its synthesis