Intro to protein biochemistry

Question 1

Function of protein (6)

Answer 1

Transport
Catalyse
Communication
Defence e.g. antibodies
Control
Structural

Question 2

Structure of amino acid (draw)

Answer 2

(h3n+) (R) c (coo-)(H)

Question 3

What happens when proteins in solution + physical pH 7

Answer 3

Assume zwitterion state

Question 4

What causes a zwitterion

Answer 4

Charged/ ionised + amino and - carboxyl group

Question 5

Primary structure

Answer 5

Covalent structure of amino acids w/ peptide bonds

Question 6

Secondary structure characteristics (3)

Answer 6

Alpha helix
Beta pleated sheets
Beta loop regions

Question 7

What causes the folding in the secondary structure

Answer 7

Hydrogen bonds between peptide bonds cO + nH

Question 8

Which part of the secondary structure is hydrophobic and which is hydrophilic

Answer 8

Beta loop region = hydrophilic therefore on exterior

Alpha helices + beta sheet folded interior to avoid watery environment

Question 9

Define hydrophilic

Answer 9

Can interact with water

lone pair of electron on electronegative oxygen interact w/ electropositive H group

Question 10

Define hydrophobic

Answer 10

Cannot interact w/ water

Polar

Question 11

Define amphipathic

Answer 11

Regions that are polar + non polar

Question 12

Characteristics of unfolded protein (3)

Answer 12

Sticky
Prone to aggregation
Prone to degradation

Question 13

Characteristic of folded 3D protein form

Answer 13

More stable

bc more bonds + more thermostable so need more energy to break

Question 14

Non covalent bonds in tertiary structure (3)

Answer 14

Hydrogen bonds
Van der Waals forces (dipole-dipole interactions)
Electrostatic interactions (salt bridges) between charged residues

Question 15

Covalent bonds in tertiary structure (2)

Answer 15

Peptide 
Disulphide bridges (s-s)

Question 16

Where disulphide bridges found + why

Answer 16

Only in secretory pathway, mitochondria, lumenal ER

bc cytoplasm v reducing which will break down bridge

Question 17

Define native structure

Answer 17

Folded, active form

Question 18

Define random coil

Answer 18

Unfolded structure w/ no secondary structure

Question 19

Define conformation

Answer 19

Change in 3D structure through rotation of bonds (no breakage)

Question 20

Define denaturation

Answer 20

Destruction of native structure by change of conformation

breaks peptide bonds but can return to active conformation

Question 21

Define degradation

Answer 21

Breaking of covalent bonds to smaller molecules

Question 22

Aim of protein homeostasis

Answer 22

Ensure correct amount of functional protein at all times

Important in diseases

Question 23

What ensures protein homeostasis (3)

Answer 23

Production (protein translation)
Folding (controls if protein functional
Trafficking (correct amount functional protein to correct part of cell, where needed)
Degradation

Question 24

What happens when protein homeostasis goes wrong

Answer 24

Chaos in cell
Stress response
Cell death