M&R 1.2 - Membrane Proteins, Membrane Asymmetry and the Cytoskeleton Flashcards Preview

ESA 2 > M&R 1.2 - Membrane Proteins, Membrane Asymmetry and the Cytoskeleton > Flashcards

Flashcards in M&R 1.2 - Membrane Proteins, Membrane Asymmetry and the Cytoskeleton Deck (21):
1

What are the functions of membrane proteins?

- Facilitated diffusion
- Maintain ion gradients
- Specificity (responses)
(Functional evidence)

2

What are the biochemical evidences for membrane proteins?

- Membrane fractionation and gel electrophoresis
- Freeze Fracture

3

How can proteins be mobile in bilayers? (4)

- Conformational changes
- Rotation
- Lateral Diffusion
- NO FLIP FLOP DUE TO LARGE HYDROPHILIC MOIETIES

4

How is the mobility of proteins restricted in the membrane? (4)

- Aggregates of proteins form together which decreases movement
- Tethering
- Interactions with other cells (stick together)
- Lipid mediated effects

5

What is tethering?

Membrane proteins hold on to the basement membrane

6

What is meant by lipid mediated effects?

Membrane proteins separate into cholesterol poor regions/ fluid phase

7

Where can membrane proteins be located in the membrane?

- Peripheral
- Integral

8

Describe peripheral membrane proteins (3)

- Surface bound by ionic or hydrogen bonds
- Associated, not integral
- Removed from bilayer by a change in pH or ionic strength

9

Describe integral membrane proteins (2)

- Interact with hydrophobic areas
- Have to be removed by aggressive means e.g. Detergents/ organic solvents as they compete for non-polar interactions.

10

How are membrane proteins inserted into the bilayer?

- Secretory pathway
- Stop transfer signal reached
- Protein is translated in cytoplasm and leaves stop transfer signal in endoplasmic reticulum therefore spanning the membrane

11

Describe the stop transfer signal

18-22 highly hydrophobic amino acids

12

Describe the amino acids that make up transmembrane proteins (4)

SHUP
- Small
- Hydrophobic
- Uncharged
- Polar

13

What happens if there are no signal peptidase sites?

- No cleavage
- N-terminal remains outside
- C-terminal remains inside

14

What is topology?

- N-terminal = in cytoplasm
- C-terminal = outside cell

15

What is the cytoskeleton?

A cage structure grafted on to the inside of the plasma membrane

16

Which proteins make up the cytoskeleton in an erythrocyte? (3 parts)

- Actin and Spectrin

- Attached to basement membrane by Ankyrin and Glycophorin

- Bound to Band 3 and Band 4.1 respectively

17

What are Ankyrin and Glycophorin?

Adaptor proteins

18

What are the two types of haemolytic anaemias?

- Hereditary Spherocytosis
- Hereditary Elliptocytosis

19

What causes haemolytic anaemias?

A mutation in the gene for Spectrin

20

Describe Hereditary Spherocytosis (4)

- Depletes Spectrin coverage by 40-50%
- Red Blood Cells become round
- Increases cell lysis
- Decreases cell lifespan

21

Describe Hereditary Elliptocytosis (3)

- Defect in the Spectrin molecule
- Can't form stable heterotetramers
- Fragile cells

Decks in ESA 2 Class (63):