This document contains a 20 question multiple choice quiz on biochemistry. It covers topics like enzyme deficiencies, electron transport chain, immunology, inborn errors of metabolism, and signal transduction. An answer key is provided at the end with the correct response for each question. The document was prepared by Anish Dhakal and provides a knowledge assessment test on various concepts in biochemistry.

1. 20 MCQs in Biochemistry
20 questions
100 marks
How much can you score?
Prepared by:
Anish Dhakal (Aryan)

2. 1. Achondroplasia, a major cause of dwarfism is a
disease that if runs in a family is typically seen in
every generation. Based on the Hardy Weinberg
principle, what is the expected frequency of
carriers of this disorder in Caucasian race?
A. 1/35000
B. 1/125000
C. 1/25000
D. 0

3. 2. During RNA synthesis, DNA template sequence
“TAGC” is transcribed to produce which of the
following sequences?
A. ATCG
B. GCTA
C. CGTA
D. GCUA

4. 3. The pathogenesis of the disease Sickle cell
anemia is a classic example of which of the
following mutation?
A. Silent mutation
B. Missense mutation
C. Nonsense mutation
D. Frameshift mutation

5. 4. An important vitamin which is constituent of the
enzymes Pyruvate carboxylase and Acetyl CoA
carboxylase has a very rare deficiency cases
clinically, most commonly seen in people
consuming large amount of raw eggs as it contains
abundant avidin. What is the vitamin implicated?
A. Vitamin B7
B. Vitamin B3
C. Vitamin B12
D. Vitamin B6

6. 5. One of the most important side effects of anti-
tubercular drug Isoniazid is sideroblastic anemia,
convulsions and stomatitis. Vitamin deficiency in
such therapy causes the symptoms. The same
Vitamin is also necessary for Heme synthesis. What
is the vitamin concerned?
A. Niacin
B. Cyanocobalamin
C. Biotin
D. Pyridoxine

7. 6. “Folate trap” occurs on not being able to supply
enough folate for the biochemical pathway which is
often due to the decrease in amount of active
folate pool in the body. Which of the following form
of tetrahydrofolate (THF) doesn’t represent active
folate pool in the body?
A. Formyl THF
B. Methyl THF
C. Methenyl THF
D. Methylene THF

8. 7. In the Heme synthesis the enzyme deficiencies
latter in the process are more clinically relevant.
The reason for this is that the accumulated
porphyrins are much more implicated for
photosensitivity than porphyrin precursors. What is
the first porphyrin in the process?
A. Porphobilinogen
B. Coproporphyrinogen III
C. Hydroxymethylbilane
D. Uroporphyrinogen III

9. 8. In regard to Electron transport chain, carbon
monoxide has similar but less severe action to
cyanide. They ultimately block the electron
transport to terminal oxygen. Which complex do
they bind in ETC?
A. Coenzyme Q
B. Complex III
C. Complex I
D. Complex IV

10. 9. Rotenone, an insecticide has the property to
block a complex in the Electron Transport Chain
hindering ATP generation from reducing
equivalents. Which complex does it bind to?
A. NADPH dehydrogenase
B. Ubiquinone
C. Cytochrome oxidase
D. Cytochrome b/c1

11. 10. A 15-month-old girl has been given an MMR
immunization. Which of the following chemical
messengers is responsible for the body’s ability to
mount an immune response to this vaccination?
A. Neuropeptides
B. Biogenic amines
C. Cytokines
D. Steroid hormones

12. 11. In a lifetime, a person may receive a dozen
tetanus toxoid inoculations. When booster dose is
administered at 10 years interval which of the
following is true for B lymphocytes that respond?
A. Their receptors would have high avidity
B. They would be large an highly metabolic
C. They would have low levels of adhesion molecules
D. They would have surface IgA, IgG or IgE

13. 12. Acute intermittent porphyria is caused due
to deficiency of:
A. PBG deaminase
B. Uroporphyrinogen III synthase
C. Ferro chelatase
D. Uroporphyrinogen decarboxylase

14. 13. Rifampicin, and antitubercular drug inhibits
DNA dependent RNA polymerase. On contrast,
eukaryotic polymerase is inhibited by a poison
often found in poisonous mushrooms called Alpha
amanitin. Which enzyme does it inhibit in
eukaryotes?
A. RNA polymerase I
B. RNA polymerase II
C. RNA polymerase III
D. DNA polymerase

15. 14. BRCA1 gene mutations does not always results
in breast or ovarian cancer. Which of the following
genetic principles best describe the phenomenon?
A. Variable expressivity
B. Pleiotropy
C. Mosaicism
D. Incomplete penetrance

16. 15. “The allele inherited from the father is silenced,
and only the allele from the mother is expressed or
vice versa.” Which of the following genetic
principles best describe the statement:
A. Imprinting
B. Locus heterogeneity
C. Allelic heterogeneity
D. Mosaicism

17. 16. Hypophosphatemic rickets, formerly known as
Vitamin D resistant rickets is an inherited disorder
causing increase phosphate wasting at proximal
tubules. It is a classic example of which pattern of
inheritance:
A. Autosomal dominant
B. Autosomal recessive
C. X-linked dominant
D. X-linked recessive

18. 17. Which of the following disease does not
represent example of X-lined recessive disease
pattern?
A. Hemophilia A
B. Hemophilia B
C. Sickle cell anemia
D. G6PD deficiency

19. 18. Huntington disease is a classic example of
trinucleotide repeat expansion disease. Which of
the following disorders are not caused by
trinucleotide repeat expansion?
A. Fragile X syndrome
B. Myotonic dystrophy
C. Angelman syndrome
D. Friedrich ataxia

20. 19. A patient with ABG profile as follows was
admitted to the ward.
pH=7.1
pCO2= 25 mmHg
HCO3 =12 mmol/L
What is the most like likely disorder?
A. Metabolic alkalosis
B. Metabolic acidosis
C. Respiratory acidosis
D. Respiratory alkalosis

21. 20. The muscarinic receptors M1 and M3 initiate
cellular transduction process by second messenger
system which ultimately initiate a cascade of
phosphorylation which will activate the cellular
enzymes further amplifying the process. Which of
the following molecule is not directly related to the
signal transduction process of above receptors:
A. Diacylglycerol (DAG)
B. Protein kinase A
C. Inositol 1,4,5-triphosphate
D. Protein kinase C

22. Answer Key:
1. D
2. D
3. B
4. A
5. D
6. B
7. D
8. D
9. A
10. C
11. D
12. A
13. B
14. D
15. A
16. C
17. C
18. C
19. B
20. B

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