Question 1

Which statement best describes the difference between B-DNA and Z-DNA?

Accepted Answer

B-DNA is right-handed with 10 base pairs per turn, while Z-DNA is left-handed with 12 base pairs per turn.

Question 2

According to Chargaff's rule, if a DNA molecule contains 30% adenine, what percentage of guanine does it contain?

Accepted Answer

20%

Question 3

Which of the following is NOT a component of a nucleotide in DNA?

Accepted Answer

A ribose sugar

Question 4

What is the main role of hydrogen bonds in the stabilization of DNA structure?

Accepted Answer

They stabilize the pairing between complementary bases (A-T and G-C).

Question 5

Which type of RNA contains an anticodon and is directly involved in protein synthesis by delivering amino acids to the ribosome?

Accepted Answer

tRNA (transfer RNA)

Question 6

A protein’s tertiary structure is primarily stabilized by which types of interactions?

Accepted Answer

Ionic, hydrophobic, hydrogen bonds, and disulfide bridges

Question 7

Which of the following amino acids is classified as nonpolar and hydrophobic?

Accepted Answer

Valine

Question 8

What is the function of the 5' cap (7-methylguanosine) in eukaryotic mRNA?

Accepted Answer

It stabilizes mRNA and assists in its recognition by ribosomes.

Question 9

Which experiment would you use to determine the sequence of amino acids in a protein?

Accepted Answer

Enzymatic cleavage using trypsin and carboxypeptidase

Question 10

Which bioelement is essential for respiration and metabolism in living organisms?

Accepted Answer

Oxygen (O)

Question 11

What is the isoelectric point ($pI$) of a protein?

Accepted Answer

The pH at which the protein has a net zero charge

Question 12

Which of the following is a macromineral important for bone structure?

Accepted Answer

Calcium (Ca)

Question 13

Which protein structure level involves the combination of multiple polypeptide chains?

Accepted Answer

Quaternary structure

Question 14

Which of the following is a role of hemoglobin in the human body?

Accepted Answer

Transporting oxygen

Question 15

Which type of chemical bond is primarily responsible for the primary structure of proteins?

Accepted Answer

Peptide (covalent) bonds

Question 16

Which amino acid is an intermediate in the synthesis of catecholamines such as adrenaline?

Accepted Answer

Tyrosine

Question 17

What is the main difference between simple and complex proteins?

Accepted Answer

Simple proteins contain only amino acids, while complex proteins contain additional groups such as heme.

Question 18

Which of the following best describes the secondary structure of proteins?

Accepted Answer

It includes alpha-helix and beta-sheet structures stabilized by hydrogen bonds.

Question 19

Which of the following is a microelement essential for enzyme function?

Accepted Answer

Zinc (Zn)

Question 20

A mutation causes the replacement of a polar amino acid with a nonpolar one in the active site of an enzyme. What is the most likely effect?

Accepted Answer

The enzyme’s activity may decrease due to altered substrate binding.

Molecular Foundations: DNA, RNA, Proteins, and Bioelements in Organic Chemistry

Study Guide - Practice Questions