Protein Structure and Function

Question 1

What is a protein?

Answer 1

Polymer of Amino Acids linked via Peptide bonds.

Question 2

What is a peptide bond?

Answer 2

Dehydration reaction between Amino (Basic) group of one amino acid and the Carboxylic (Acidic) group of another amino acid.

Question 3

Are peptide bonds able to rotate? if not where can rotation occur?

Answer 3

No, rotation can occur at the single bonds between the C-R atom and it’s neighbours.

Question 4

Are the ‘R’ groups of amino acids more likely to be cis or trans? and why?

Answer 4

Trans, there is repulsion between cis side chains meaning cis is less stable.

Question 5

What marks the start of a polypeptide?

Answer 5

N-terminus

Question 6

What does N-terminus stand for?

Answer 6

N indicates the Amino group which contains Nitrogen.

Question 7

What marks the start of a polypeptide?

Answer 7

C-Terminus

Question 8

What does C-terminus stand for?

Answer 8

C Indicates Carboxylic group which contains Carbon

Question 9

What defines the shape that a polypeptide will have?

Answer 9

The chemical properties of the amino acids and their sequence.

Question 10

Name the 2 types of secondary structures?

Answer 10

Beta sheets and Alpha Helices

Question 11

What is the formation of secondary structures driven by?

Answer 11

Hydrogen bonds forming between the polypeptide backbone.

Question 12

Which 2 types of ‘R’ groups have more affinity for beta sheet structures?

Answer 12

large aromatic rings and beta-branched ‘R’ groups.

Question 13

What are the 3 bonds/interactions involved in the forming of a quaternary structure?

Answer 13

1. Ionic interactions
2. hydrogen bonding
3. hydrophobic interactions

Question 14

Can quaternary structures be dynamic?

Answer 14

yes

Question 15

What are the 3 protein structural categories mentioned in the lecture?

Answer 15

1. Globular
2. Fibrous
3. Membrane Proteins

Question 16

Are globular proteins soluble?

Answer 16

yes

Question 17

Are fibrous proteins soluble?

Answer 17

no

Question 18

How would you differentiate the primary and secondary structure of globular vs. fibrous proteins?

Answer 18

Globular have irregular seq. and structure

Fibrous is often repetitive at the primary and secondary level

Question 19

Are globular proteins stable??

Answer 19

they have a lower stability

Question 20

Are fibrous proteins stable??

Answer 20

yes, highly.

Question 21

Give 3 examples of globular proteins

Answer 21

1. enzymes
2. hemoglobin
3. antibodies

Question 22

Give 3 examples of fibrous proteins

Answer 22

1. Keratin
2. Actin
3. Collagen

Question 23

Contrast Globular and fibrous proteins in terms of quaternary structure

Answer 23

Globular proteins of have little to no structure on the quaternary level.

Fibrous proteins have a high level of quaternary structure

Question 24

List 4 functions of (trans) Membrane Proteins

Answer 24

1. Transport
2. signalling
3. adhesion
4. Reception

Question 25

What (secondary) structure do the TM section of Membrane Proteins often have?

Answer 25

Alpha Helix (single or bundle)

Question 26

Whats another organelle specific (secondary) structure that the TM section of Membrane Proteins can have? (name the organelle also)

Answer 26

Beta-barrel, found in the mitochondria