Ch. 22b Post-Translational Processing & Genetic Code (Final Exam)

Question 1

Why does post-translational processing occur?

Answer 1

The polypeptide coming from the ribosome is inactive

Question 2

What are the 4 structures of protein folding?

Answer 2

Primary, secondary, tertiary, and quarternary

Question 3

Protein folding is aided by molecular chaperons. Where do they bind?

Answer 3

Hydrophobic regions of proteins

Question 4

Why is chaperon binding important?

Answer 4

They keep protein in open conformation until it is ready to fold

Question 5

What are the 2 functions of proteolytic cleavage?

Answer 5

1) Trimming to remove pieces of the N and/or C terminal to provide a shortened active protein
2) Cutting polypeptides into active protein segments

Question 6

What drug is a common result of proteolytic cleavage?

Answer 6

Insulin

Question 7

Post-translational chemical modification involves the…

Answer 7

Addition of small chemical functional groups to animo acids

Question 8

What is the most common mode of chemical modification in animal cells?

Answer 8

Protein phosphorylation

Question 9

Chemical modification promotes…

Answer 9

Protein diversity

Question 10

What 3 amino acids are subjected to phosphorylation?

Answer 10

Serine, tyrosine, and theonine

Question 11

What is the premise of protein degradation/ubiquitination?

Answer 11

Adding ubiquitin to misfolded proteins

Question 12

What does the proteasome do once a protein is tagged with ubiquitin?

Answer 12

The proteasome recognizes the need for degradation into peptide subunits

Question 13

In sum, how do post-translational mods affect proteins?

Answer 13

They change the structure, dynamics, behavior, and characteristics of proteins to allow for full activity

Question 14

What do you call codons that code for the same amino acids?

Answer 14

Synonomous

Question 15

Out of the 64 possible codons, how many represent amino acids, and how many are stop codons?

Answer 15

61 - represent
3 - stop codons

Question 16

The tendency for identical or chemically similar amino acids to be represented by related codons minimizes…

Answer 16

The likelihood that a single base pair change will result in mutation

Question 17

Are codons with chemically similar amino acids similar or different in sequence?

Answer 17

Similar

Question 18

What is third-base degeneracy?

Answer 18

The insignificance of the base in a codon’s 3rd position (3’ end)

Question 19

Why is a codon’s 3rd base in a set of 4 codons insignificant?

Answer 19

Often, the 4 codons only differ in the 3rd base and represent the same amino acid

Question 20

What is the principle behind the wobbling hypothesis?

Answer 20

Multiple codons encoding the same amino acid most often differ at the 3rd base position

Question 21

Does each triplet codon require its own tRNA with a complementary anticodon, or can a single tRNA respond to related codons?

Answer 21

Often, 1 tRNA can recognize more than one codon

Question 22

An mRNA codon’s 3rd base position is a tRNA anticodon’s { } base position.

Answer 22

1st

Question 23

What explanation did Crick give for the wobble hypothesis?

Answer 23

The anticodon’s 5’ end doesn’t have strict base-pairing requirements, so it can form hydrogen bonds with several bases at the codon’s 3’ end

Question 24

Which ribosomal site permits the increased flexibility at the anticodon’s 1st base?

Answer 24

A

Question 25

What would happen if the genetic code was no degenerative (i.e. allow for wobbling)?

Answer 25

Only 20 codons would code amino acids, and 44 would be stop codons, resulting in mutation

Question 26

Anticodon 1st position base U corresponds to this codon 3rd position base(s).

Answer 26

A or G

Question 27

Anticodon 1st position base C corresponds to this codon 3rd position base.

Answer 27

G

Question 28

Anticodon 1st position base A corresponds to this codon 3rd position base.

Answer 28

U

Question 29

Anticodon 1st position base G corresponds to this codon 3rd position base(s).

Answer 29

C or U