Chapter 9

Question 1

What is the primary structure of a protein?

Answer 1

The linear sequence of amino acids linked by peptide bonds.

Question 2

Which end of a protein corresponds to the 5′ end of mRNA?

Answer 2

The N-terminus (amino group).

Question 3

What are two common secondary structures in proteins?

Answer 3

Alpha helix and beta sheet (formed by hydrogen bonding)

Question 4

How do codon and anticodon relate in orientation?

Answer 4

Codon on mRNA (5′→3′), anticodon on tRNA (3′→5′, complementary).

Question 5

Why does a specific tRNA carry a specific amino acid?

Answer 5

Aminoacyl-tRNA synthetase recognizes both the tRNA and its amino acid.

Question 6

What is the function of 16S rRNA in bacteria?

Answer 6

It recognizes the Shine-Dalgarno sequence for translation initiation.

Question 7

What happens at the A, P, and E sites of the ribosome?

Answer 7

A site: Incoming aminoacyl-tRNA binds.
P site: Peptidyl-tRNA holds growing chain.
E site: Exit for uncharged tRNA.

Question 8

What are the three stop codons?

Answer 8

UAA, UAG, UGA.

Question 9

What is the pathway for secreted proteins?

Answer 9

Ribosome → Rough ER → Golgi → Vesicles → Membrane/secretion.

Question 10

What does the wobble hypothesis explain?

Answer 10

Flexibility at the third base of the codon allows multiple codons to code for the same amino acid.

Question 11

What sequence context helps AUG recognition in eukaryotes?

Answer 11

Kozak sequence.

Question 12

What sequence does 16S rRNA recognize in prokaryotes?

Answer 12

Shine-Dalgarno sequence.

Question 13

Define phosphorylation in one sentence

Answer 13

Phosphorylation: Adds phosphate group to regulate activity.

Question 14

Define glycosylation in one sentence

Answer 14

Glycosylation: Adds sugar chains for stability and recognition.

Question 15

Define ubiquitination in one sentence

Answer 15

Ubiquitination: Tags proteins for degradation or alters function.

Question 16

If the mRNA codon is 5′ AUG 3′, what is the anticodon?

Answer 16

3′ UAC 5′ (complementary and antiparallel).

Question 17

Why is the anticodon written 3′ → 5′?

Answer 17

Because it pairs antiparallel to the mRNA codon (which is 5′ → 3′).

Question 18

If the DNA template strand is 3′ TAC 5′, what is the mRNA codon?

Answer 18

5′ AUG 3′ (replace T with U).

Question 19

If the DNA coding strand is 5′ ATG 3′, what is the mRNA codon?

Answer 19

5′ AUG 3′ (same sequence except U replaces T).

Question 20

If the stop codon is UAG, what is the anticodon and DNA template?

Answer 20

Anticodon: 3′ AUC 5′
DNA template: 3′ ATC 5′.

Question 21

Which strand is complementary to mRNA?

Answer 21

DNA template strand (3′ → 5′).