Biochemistry Biochemical Techniques and Methods

Question 1

SDS-PAGE separates proteins primarily based on:

Accepted Answer

Molecular weight (size)

Answer

Net charge at physiological pH

Answer

Isoelectric point

Answer

Hydrophobicity

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

To block non-specific binding sites

Answer

To generate a detectable signal directly

Answer

To transfer protein from gel to membrane

Question 3

The polymerase chain reaction (PCR) requires which enzyme?

Accepted Answer

Thermostable DNA polymerase (Taq polymerase)

Answer

RNA polymerase

Answer

Reverse transcriptase

Answer

DNA ligase

Question 4

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

Accepted Answer

Affinity chromatography

Answer

Size-exclusion chromatography

Answer

Ion-exchange chromatography

Answer

Reverse-phase HPLC

Question 5

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

Accepted Answer

Enzyme-conjugated antibodies producing a colorimetric signal

Answer

Radioactively labeled antibodies (RIA method)

Answer

Fluorescent dyes that stain all proteins nonspecifically

Answer

Electric current to detect protein migration

Question 6

Which technique is used to determine the three-dimensional structure of proteins at atomic resolution using X-rays?

Accepted Answer

X-ray crystallography

Answer

Nuclear magnetic resonance (NMR) spectroscopy

Answer

Cryo-electron microscopy (cryo-EM)

Answer

Circular dichroism (CD) spectroscopy