Biochemistry Biochemical Techniques and Methods

Question 1

SDS-PAGE separates proteins primarily based on:

Accepted Answer

Molecular weight (size)

Answer

SDS denatures proteins and coats them with uniform negative charge proportional to mass, so migration in the polyacrylamide gel reflects molecular weight only.

Question 2

In a Western blot, after SDS-PAGE and transfer to membrane, what is the purpose of the primary antibody?

Accepted Answer

To specifically recognize the target protein

Answer

The primary antibody binds specifically to the target protein (antigen) on the membrane, providing specificity; a secondary antibody conjugated to an enzyme or fluorophore then generates the detectable signal.

Question 3

The polymerase chain reaction (PCR) requires which enzyme?

Accepted Answer

Thermostable DNA polymerase (Taq polymerase)

Answer

PCR uses a thermostable DNA polymerase (typically Taq from Thermus aquaticus) that retains activity through the high-temperature denaturation cycles required to separate DNA strands.

Question 4

Which chromatographic technique separates molecules based on their specific binding interaction with an immobilized ligand?

Accepted Answer

Affinity chromatography

Answer

Affinity chromatography exploits specific, reversible binding between a target molecule and an immobilized ligand (e.g., His-tag/Ni-NTA, antibody/antigen) to achieve high-purity protein isolation.

Question 5

An ELISA (enzyme-linked immunosorbent assay) detects a target molecule using:

Accepted Answer

Enzyme-conjugated antibodies producing a colorimetric signal

Answer

ELISA uses antibodies conjugated to enzymes (e.g., HRP or alkaline phosphatase) that convert a substrate into a colored product, allowing quantitative detection of antigens.

Biochemistry Practice Test

Biochemistry Practice Test

Biochemistry Biochemical Techniques and Methods