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Essential Biochemistry - Protein Metabolism (Section 5)

1
Which of the following is a feature of positive nitrogen balance?
Answer
(C)
Nitrogen intake is greater than nitrogen excretion.
2
What is the fate of homogentisic acid in alkaptonuria?
Answer
(A)
Excreted in urine
3
Which amino acid is primarily responsible for carrying nitrogen to the liver for the urea cycle?
Answer
(D)
Glutamine
4
What is the normal level of blood urea nitrogen (BUN) in a healthy adult?
Answer
(B)
10-20 mg/dL
5
What enzyme catalyzes the reaction that forms urea?
Answer
(A)
Arginase
6
In the Urea Cycle, where does the urea production take place?
Answer
(B)
Cytosol
7
Which of the following conditions can lead to elevated blood urea nitrogen (BUN) levels?
Answer
A
B
C
8
What is the role of orotic acid in the context of pyrimidine synthesis?
Answer
(B)
It is an intermediate in pyrimidine synthesis.
9
What is the primary function of the urea cycle?
Answer
(B)
To eliminate ammonia from the body.
10
What is the significance of elevated levels of ammonia in the blood?
Answer
(B)
It can lead to neurological dysfunction.
11
What is the primary source of sulfur in the synthesis of cysteine?
Answer
(B)
Methionine
12
What is the significance of nitrogen balance?
Answer
A
B
D
13
What is the rate-limiting enzyme of urea cycle?
Answer
(A)
Carbamoyl phosphate synthetase I
14
What is the significance of the urea cycle?
Answer
(B)
It detoxifies ammonia.
15
Where does the urea cycle primarily occur?
Answer
(B)
Liver
16
What happens to the carbon skeletons of ketogenic amino acids?
Answer
(B)
They are converted to ketone bodies.
17
Which of the following compounds act as nitrogen donors in the urea cycle?
Answer
A
B
C
18
Which of the following amino acids can be converted to acetyl-CoA?
Answer
(C)
Leucine
19
Which of the following is NOT a substrate for the urea cycle?
Answer
(D)
Acetyl-CoA
20
Which of the following molecules is NOT directly involved in the urea cycle?
Answer
(D)
Serine
21
Which of the following molecules provides the second nitrogen atom in the urea molecule?
Answer
(B)
Aspartate
22
Which of the following amino acids are purely ketogenic?
Answer
A
B
23
Which of the following amino acids is involved in the formation of the neurotransmitter serotonin?
Answer
(B)
Tryptophan
24
Which of the following is true regarding the degradation of lysine?
Answer
(C)
It yields acetoacetyl-CoA as a product.
25
What is the primary function of tyrosine?
Answer
(A)
Precursor for melanin synthesis
26
What vitamin is involved in the metabolism of one-carbon units?
Answer
(C)
Folate
27
Where does protein digestion begin?
Answer
(B)
Stomach
28
The following enzymes are involved in digestion and absorption of protein, except:
Answer
(B)
Amylase
29
What role does BH4 play in amino acid metabolism?
Answer
(A)
It is involved in the hydroxylation of phenylalanine.
30
What is the significance of the enzyme tetrahydrofolate reductase?
Answer
(A)
It reduces dihydrofolate to tetrahydrofolate
31
Which compounds are produced from the degradation of phenylalanine and tyrosine?
Answer
(A)
Fumarate and acetoacetate
32
What is the term for the process where the amino group is removed from an amino acid?
Answer
(B)
Oxidative deamination
33
What is the role of carbamoyl phosphate synthetase I in the urea cycle?
Answer
(C)
To convert ammonia and carbon dioxide into carbamoyl phosphate.
34
Which of the following are symptoms of urea cycle disorders?
Answer
A
B
C
D
35
Which of the following is a precursor for the synthesis of glutathione?
Answer
(D)
All of the above
36
What are the common causes of elevated blood ammonia levels (Hyperammonemia)?
Answer
A
C
37
Which amino acid is involved in the formation of heme?
Answer
(A)
Glycine
38
Which of the following amino acids yields fumarate during degradation?
Answer
(D)
Proline
39
Which amino acid is the primary nitrogen donor in the urea cycle?
Answer
(C)
Aspartate
40
Which enzyme catalyzes the formation of carbamoyl phosphate in the urea cycle?
Answer
(B)
Carbamoyl phosphate synthetase I
41
Which of the following statements is correct regarding the catabolism of the carbon skeletons of amino acids?
Answer
(C)
Amino acids can be converted to either glucose or ketone bodies.
42
What is a direct product of the Urea cycle?
Answer
(B)
Urea
43
What is the major role of glutamine in the liver?
Answer
(B)
Ammonia detoxification
44
Which amino acid is NOT directly involved in the urea cycle?
Answer
(D)
Alanine
45
What is the source of one-carbon units in the synthesis of thymidine?
Answer
(A)
Folate
46
What is the function of tetrahydrofolate (THF) in one-carbon metabolism?
Answer
(A)
It carries one-carbon units.
47
What enzyme is deficient in phenylketonuria (PKU)?
Answer
(B)
Phenylalanine hydroxylase
48
What initiates the conversion of pepsinogen to pepsin?
Answer
(C)
Pepsin
49
Which of the following is a source of one-carbon units?
Answer
(C)
Tryptophan
50
What compound is formed in the first step of the conversion of methionine to cysteine?
Answer
(B)
Homocysteine