Question 1

Which of the following best describes a zwitterion at physiological pH?

Accepted Answer

A molecule with both positive and negative charges, resulting in a net neutral charge.

Question 2

Which of the following amino acids is classified as non-polar and aliphatic?

Accepted Answer

Leucine

Question 3

A peptide bond is formed between which two groups of adjacent amino acids?

Accepted Answer

The carboxyl group of one amino acid and the amino group of the next amino acid

Question 4

Which technique is most appropriate for separating proteins based on their size?

Accepted Answer

Size exclusion chromatography

Question 5

Given a protein with a theoretical isoelectric point ($$pI) of 5.5$$, at which pH would the protein carry a net negative charge?

Accepted Answer

At pH 7.0

Question 6

Which of the following mutations is considered conservative?

Accepted Answer

Replacing glutamic acid with aspartic acid

Question 7

A gene sequence contains the following open reading frame (ORF): ATG-GCC-TAA. What is the corresponding amino acid sequence?

Accepted Answer

Methionine-Alanine

Question 8

Which of the following best describes the main chain of a polypeptide?

Accepted Answer

The repeating backbone of peptide bonds, excluding side chains

Question 9

In ion exchange chromatography, which factor most directly affects the elution order of proteins?

Accepted Answer

The net charge of the protein at the buffer pH

Question 10

Which of the following statements about Fischer projections is correct?

Accepted Answer

Horizontal bonds are assumed to project toward the viewer, and vertical bonds are assumed to project away from the viewer.

Question 11

A protein is purified using affinity chromatography. What property of the protein is most critical for its retention on the column?

Accepted Answer

Its ability to bind specifically to the immobilized ligand

Question 12

Which of the following amino acids contains an aromatic side chain?

Accepted Answer

Phenylalanine

Question 13

If a mutation changes a codon from $$	ext{GAA} to$$ $$	ext{GAG}$$, what type of mutation has occurred?

Accepted Answer

A silent mutation

Question 14

Which of the following best describes a non-coding strand in DNA?

Accepted Answer

The strand that serves as a template for RNA synthesis

Question 15

Which of the following is the correct one-letter code for the amino acid tryptophan?

Accepted Answer

W

Question 16

A peptide has the sequence Ala-Gly-Ser. Which terminus is the amino group located on?

Accepted Answer

N-terminus

Question 17

Which of the following best explains why SDS-PAGE separates proteins primarily by size?

Accepted Answer

SDS denatures proteins and coats them with negative charge, minimizing differences in shape and charge.

Question 18

Which of the following is true about chiral carbon atoms in amino acids?

Accepted Answer

They can exist as left- or right-handed mirror images (enantiomers).

Question 19

A protein sample is loaded onto a cation exchange column at pH 6.0. The protein has a $$pI of 8.0. $$What will happen?

Accepted Answer

The protein will bind to the column because it is positively charged at pH 6.0.

Question 20

Which of the following best describes the role of an open reading frame (ORF) in gene expression?

Accepted Answer

It is a section of DNA that contains a continuous sequence between a start and stop codon, coding for a protein.

Fundamental Concepts in Biochemistry: Amino Acids, Protein Structure, and Purification Techniques

Study Guide - Practice Questions