ICPP 1 Membrane Bilayer - Lipids

Question 1

What are functions of the membrane?

Answer 1

Highly selective barrier
Control of enclosed electrochemical environment
Communication
Recognition
Signalling
Adhesion protein
Immune surveillance - communication
Signal generation to response to stimuli

Question 2

What is the membrane composition by dry weight?

Answer 2

40% lipid
60% protein
1-10% carbs

Question 3

How much of membrane weight is water?

Answer 3

20%

Question 4

Role of water in membranes

Answer 4

Interacts with charged/polar regions + stabilises lipid head regions

Question 5

What are the types of lipids?

Answer 5

Glycolipids
Cholesterol
Phospholipids - saturated + unsaturated

Question 6

Types of unsaturated chains

Answer 6

Cis - kink
Trans - straight leg

Question 7

What type of chain will make the membrane more fluid and why?

Answer 7

Cis unsaturated chain
Less tightly packed together due to kinks

Question 8

Amphipathic meaning

Answer 8

Includes both hydrophobic + hydrophilic parts

Question 9

Composition of phospholipid

Answer 9

Hydrophilic phosphate head + polar group
Glycerol backbone
Hydrophobic fatty acid tails

Question 10

What type of reaction is between the fatty acid tails + glycerol back bone in phospholipids?

Answer 10

Esterification reaction

Question 11

What enables phospholipid head + tails to rotate?

Answer 11

Glycerol residual has single bonds

Question 12

Types of polar groups attached to the phosphate head in phospholipids

Answer 12

Amines
Amino acids
Choline - most common
Inositol - source of secondary messanger

Question 13

What makes phospholipids optimally energetically stable?

Answer 13

External hydrophilic head
Internal hydrophilic tails

Question 14

What is a sphinogomyelin?

Answer 14

Phospholipid without glycerol backbone
Has a sphingosine molecule instead

Question 15

How are sphinogomyelin synthesised?

Answer 15

Bringing together a fatty acid chain + sphingosine molecule

Question 16

What do sphingosine molecules have?

Answer 16

Serine residual -NH group

Question 17

What can be the head group in sphinogomyelins?

Answer 17

Choline
Ethanolamine

Question 18

What are the fatty acid chains mainly in sphinogomyelins?

Answer 18

Mainly saturated FA
If unsaturated FA > trans > no kink > closer packing

Question 19

Function of sphinogomyelins

Answer 19

Membrane protein orientation
Formation of lipid rafts

Question 20

Composition of sphinogomyelins

Answer 20

Head group - choline or ethanolamine
Sphingosine molecule
Fatty acids - mainly saturated

Question 21

Composition of glycolipids

Answer 21

No phosphate had
No glycerol backbone - sphingosine molecule instead
Fatty acid chains

Question 22

Where are glycolipids located?
What for?

Answer 22

Only on external membrane for signalling

Question 23

Classes of glycolipids

Answer 23

Cerebrosides
Gangliosides

Question 24

Head group in cerebroside

Answer 24

Glucose
Galactose

Question 25

Where is there a high concentration of sphinogomyelins?

Answer 25

Myelin sheath

Question 26

Where is there a high concentration of cerebrosides?

Answer 26

Myelin sheath Nervous system

Question 27

Function of cerebrosides

Answer 27

Stabilises membrane Cell to cell recognition Form basis of blood group - antigens on RBCs Lipid raft formation

Question 28

What is connected to the head group in gangliosides?

Answer 28

Oligosaccharide chain

Question 29

Function of gangliosides

Answer 29

Cell-cell signalling Immune system - important in CNS Lipid raft formation

Question 30

Where are gangliosides on membranes?

Answer 30

Extend out from cell surface

Question 31

What are steroids derived from?

Answer 31

Cholesterol

Question 32

Composition of cholesterol

Answer 32

-OH head - hydrophilic Non-polar hydrocarbon tail - hydrophobic

Question 33

Function of cholesterol

Answer 33

Membrane fluidity control Lipid raft formation Extending temp rang of membrane

Question 34

Relationship between permeability of membrane + structural integrity

Answer 34

**Reciprocal** Increase in permeability = decreased in structural integrity + vice versa

Question 35

List the ways lipids can move

Answer 35

Fast axial rotation Fast lateral diffusion Protrusion Wave 3D undulations Flip flop

Question 36

Describe fast axial rotation

Answer 36

Whole lipid spins on head-tail axis In circles

Question 37

Describe fast lateral diffusion

Answer 37

Lipids move randomly side to side through bilayer

Question 38

Describe protrusion

Answer 38

Bobbing up + down on vertical axis

Question 39

Describe wave 3D undulations

Answer 39

Like Mexican wave

Question 40

Describe flip flop movement

Answer 40

Lipid flips upside down

Question 41

What does adding unsaturated phospholipids to the membrane do?

Answer 41

Increases fluid using due to cis chains Less close packing Gel/fluid state

Question 42

What does adding unsaturated phospholipids to the membrane do?

Answer 42

Increased membrane stability Acts as a buffering molecule - extends temp. range

Question 43

What are lipid rafts?

Answer 43

Areas of organised/specialised distribution of lipids

Question 44

Components of lipid rafts

Answer 44

Cholesterol Sphinogomyelins Saturated glycolipids

Question 45

Function of lipid rafts

Answer 45

- Provides more stable environment for signalling proteins - Stabilises + organises proteins - Acts as organising domain for receptors or signalling molecules - Optimises kinetic interaction for signal transduction

Question 46

What features does the components of lipid rafts allow?

Answer 46

Strong interaction > tight packing > decreased movement + fluidity

Question 47

What is there a reduced amount of in lipid rafts?

Answer 47

Unsaturated chain phospholipids