Deck 27: Protein and Amino Acid Metabolism

Question 1

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

Answer 1

10-20

Question 2

Two key amino acids in the catabolism of nitrogen atoms in amino acids are

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

Answer 2

aspartate and glutamate.

Question 3

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.

Answer 3

transaminase.

Question 4

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

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

Question 5

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

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

Question 6

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 7

The first step in amino acid catabolism is ________.

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

Question 8

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

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

Question 9

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 10

When the amine 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 11

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 12

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 13

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

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

Question 14

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 15

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 16

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 17

The structural formula of glutamate is ________.

A)

B)NH₄⁺
C)

D)

E)

Question 18

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

Question 19

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

Question 20

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 21

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

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

Question 22

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 23

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 24

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

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

Question 25

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 26

The conversion of nitrogen derivatives to urea takes place in the

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

Question 27

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 28

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

Question 29

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 30

The urea cycle is part of the metabolic breakdown of ________.

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

Question 31

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 32

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 33

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

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

Question 34

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 35

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

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

Question 36

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 37

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

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

Question 38

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 39

The structural formula of urea is ________.

A)

B)NH₄⁺
C)

D)

E)

Question 40

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 41

Match the following.
nonessential amino acid

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

Question 42

Match the following.
amino acid pool

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

Question 43

Match the following.
glucogenic amino acid

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

Question 44

Match the following.
urea cycle

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

Question 45

Match the following.
essential amino acid

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

Question 46

Match the following.
transamination

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

Question 47

Match the following.
ketogenic amino acid

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