Membrane biology and transport

Question 1

What model is used for the cell membrane?

Answer 1

Fluid mosaic model

Question 2

What are phospholipids?

Answer 2

The basic component of cell membranes
Hydrophillic Head
Hydrophobic tail

Question 3

What is cholesterol’s role in the membrane?

Answer 3

To regulate fluidity

Question 4

How much of the membrane volume is protein?

Answer 4

Around 50%

Question 5

What protein % does mitochondrial membranes have?

Answer 5

80%

Question 6

What are the three types of integral proteins?

Answer 6

Single, Multipass and Polytopic

Question 7

What are single transmembrane proteins?

Answer 7

Only passes through the membrane once

Question 8

What are Multipass transmembrane proteins?

Answer 8

The protein passes through the membrane multiple times

Question 9

What are polytopic transmembrane proteins?

Answer 9

Passes through the membrane multiple times but as a beta-sheet

Question 10

What is a Amphipathic protein?

Answer 10

Passes through the extracellular side of the membrane once

Question 11

What is a Hydrophobic loop protein?

Answer 11

The protein enters the extracellular side of the membrane multiple times

Question 12

What does a electrostatic protein do?

Answer 12

Binds to the hydrophillic parts of the membrane

Question 13

What do anchored proteins do?

Answer 13

Covalently bond to the lipid “anchor” Glycosylphosphatidylinositol (GPI)

Question 14

How is fluidity affected?

Answer 14

Cholesterol - More cholesterol = less fluid
Temperature - Lower temp = less fluid
Phospholipids - Longer chains = less fluid
Saturated chains = less fluid

Question 15

What is a lipid raft?

Answer 15

An area that’s rich in cholesterol and sphingomyelin

Question 16

How does membrane permeability change?

Answer 16

Charge
Polarity
Size

Question 17

How does facilitated diffusion work?

Answer 17

High -> low concentration
Uses channels/carriers
e.g. Ion channels, Water via aquaporins

Question 18

How does active transport work?

Answer 18

Low -> high concentration
Uses ATP
e.g. Ion pumps

Question 19

How are channels/carriers controlled?

Answer 19

Ligand gated
Mechanically gated
Always open
Voltage gated

Question 20

How do voltage-gated ion channels work?

Answer 20

They detect changes in membrane potential
Na+, K+, Ca2+ channels
Inactivation causes refractory period

Question 21

What do amino acids do in ion channels?

Answer 21

They selectively filter different ions

Question 22

What do amino acids do in voltage channels?

Answer 22

They have a voltage sensing helix

Question 23

What is endocytosis?

Answer 23

The cell engulfs an external substance and contains it within a vesicle

Question 24

What is exocytosis?

Answer 24

Cell secretes a substance contained within a vesicle

Question 25

How are ion gradients established?

Answer 25

Through precise control of which ions enter/exit

Question 26

What do membrane potentials allow?

Answer 26

Electrical signalling and excitability
Energy production

Question 27

What is the purpose of receptors?

Answer 27

Allows a molecule to affect the cell without entering

Question 28

What is the largest and most diverse group of receptors?

Answer 28

G-Protein coupled receptors

Question 29

What does an activated G protein activate?

Answer 29

A second messenger