Sign In

Essential Biochemistry - Protein Metabolism (Section 3)

1
What are the main end products of purine degradation?
Answer
(A)
Uric acid
2
Which of the following is/are important in the synthesis of melanin?
Answer
A
B
3
What is the precursor for the synthesis of citrulline in the urea cycle?
Answer
(B)
Ornithine and carbamoyl phosphate
4
What is the role of ornithine in the urea cycle?
Answer
(C)
It is an intermediate which regenerates to continue the cycle.
5
Which amino acid is degraded to acetoacetate?
Answer
(B)
Lysine
6
Phenylketonuria results due to the absence of the enzyme:
Answer
(B)
Phenylalanine hydroxylase
7
Which of the following is the most important nitrogenous waste product in mammals?
Answer
(B)
Urea
8
Which of the following conditions is due to a defect in tyrosine metabolism?
Answer
(D)
Tyrosinemia
9
Which of the following is the starting material for the synthesis of melanin?
Answer
(B)
Tyrosine
10
Which of the following compounds is formed from tyrosine via a series of reactions involving DOPA?
Answer
(A)
Melanin
11
What are the primary functions of transamination reactions in amino acid metabolism?
Answer
A
C
12
What is the role of tetrahydrofolate (THF) in one-carbon metabolism?
Answer
(D)
All of the above
13
What are the roles of ammonia in the body?
Answer
A
C
D
14
Which vitamin is a precursor to niacin?
Answer
(D)
Vitamin B3
15
Which of the following is NOT an endopeptidase?
Answer
(D)
Carboxypeptidase
16
Which of the following is NOT a feature of phenylketonuria (PKU)?
Answer
(D)
Increased production of tyrosine
17
Which enzyme is involved in the first step of transamination?
Answer
(A)
Transaminase
18
What is the final step of the urea cycle?
Answer
(C)
Hydrolysis of arginine to urea and ornithine.
19
Which of the following is the precursor for the synthesis of serotonin?
Answer
(A)
Tryptophan
20
Which is the most significant pathway for the conversion of tryptophan?
Answer
(B)
Kynurenine pathway
21
Which of the following diseases is linked to defects in branched-chain amino acid metabolism?
Answer
(B)
Maple syrup urine disease
22
Which of the following is a characteristic of a negative nitrogen balance?
Answer
(C)
Nitrogen excretion exceeds nitrogen intake.
23
Which of the following is NOT a precursor for the synthesis of urea?
Answer
(D)
Acetyl-CoA
24
What condition is characterized by a deficiency in cystathionine beta-synthase?
Answer
(C)
Homocystinuria
25
What is the primary function of proteins in the body?
Answer
(B)
Building and repairing tissues
26
Which type of reaction is conversion of norepinephrine to epinephrine?
Answer
(C)
Transmethylation
27
What is the product of the kynurenine pathway?
Answer
(C)
Niacin
28
The synthesis of cysteine from serine and homocysteine requires which vitamin?
Answer
(B)
B6
29
What is the first step in the catabolism of most amino acids?
Answer
(A)
Transamination
30
Which of the following is NOT a typical symptom of hyperammonemia?
Answer
(C)
Increased appetite
31
Which enzyme is responsible for the oxidative deamination of glutamate?
Answer
(B)
Glutamate dehydrogenase
32
Which of the following enzyme is deficient in PKU?
Answer
(B)
Phenylalanine hydroxylase
33
Which of the following amino acids can undergo deamination by dehydration?
Answer
(A)
Threonine
34
In Maple-syrup urine disease, which of the following compounds is accumulated?
Answer
(C)
Branched chain α-keto acids
35
Which of the following amino acids can be directly converted to pyruvate?
Answer
(A)
Alanine
36
Which of the following is NOT a source of one-carbon groups?
Answer
(D)
Threonine
37
Which of the following are common symptoms of urea cycle disorders?
Answer
A
B
C
D
38
The reactions of urea cycle occur in:
Answer
C
D
39
Tetrahydrobiopterin is used as a coenzyme in the metabolism of:
Answer
(B)
Phenylalanine
40
Which of the following amino acids is the starting material for the synthesis of proline?
Answer
(A)
Glutamate
41
Which compound(s) is/are produced by the decarboxylation of tryptophan?
Answer
A
B
C
42
What is the key function of serotonin in the body?
Answer
(A)
Regulation of mood
43
Which of the following factors can affect the blood urea nitrogen (BUN) levels?
Answer
A
B
C
D
44
What is the overall purpose of amino acid catabolism?
Answer
(C)
To generate energy.
45
Transamination of oxaloacetate results in the formation of:
Answer
(A)
Aspartic acid
46
What is the first step in the urea cycle?
Answer
(B)
Formation of carbamoyl phosphate.
47
What is the role of serine in the body?
Answer
(B)
Precursor for the synthesis of glycine
48
What are the end products of the urea cycle?
Answer
(B)
Urea and fumarate.
49
Which of the following is the primary source of ammonia in the urea cycle?
Answer
(C)
Glutamate
50
Which amino acid is the precursor for the synthesis of creatine?
Answer
(A)
Glycine