MBBS Biochemistry

Question 1

Which enzyme is deficient in Phenylketonuria (PKU)?

Accepted Answer

Phenylalanine hydroxylase

Answer

Phenylalanine transaminase

Answer

Tyrosine aminotransferase

Answer

Homogentisate oxidase

Question 2

In which organelle does the citric acid (Krebs) cycle occur?

Accepted Answer

Mitochondrial matrix

Answer

Cytoplasm

Answer

Smooth endoplasmic reticulum

Answer

Nucleus

Question 3

Hemoglobin S (sickle cell) differs from hemoglobin A by a substitution of which amino acid?

Accepted Answer

Valine replaces glutamate at position 6 of the beta chain

Answer

Glutamate replaces valine at position 6 of the beta chain

Answer

Lysine replaces glutamate at position 6 of the alpha chain

Answer

Serine replaces threonine at position 6 of the beta chain

Question 4

Which vitamin serves as a coenzyme for pyruvate dehydrogenase?

Accepted Answer

Thiamine (B1)

Answer

Riboflavin (B2)

Answer

Niacin (B3)

Answer

Biotin (B7)

Question 5

DNA replication proceeds in which direction?

Accepted Answer

Bidirectional from multiple origins but always 5' to 3'

Answer

3' to 5' only

Answer

5' to 3' only

Answer

Both 3' to 5' and 5' to 3' simultaneously

Question 6

Which enzyme catalyzes the rate-limiting step of glycolysis?

Accepted Answer

Phosphofructokinase-1 (PFK-1)

Answer

Hexokinase

Answer

Pyruvate kinase

Answer

Phosphoglucose isomerase