Membrane Structure

Question 1

Describe water in terms of membranes

Answer 1

Most abundant substance in organisms > Cytosol and extracellular medium
Polarised molecule with partial neg charge on O2

Question 2

Describe lipids in terms of membranes

Answer 2

No net charge, non polarised molecule

Form barrier in cell membranes separating cytosol and extracellular medium

Question 3

What are the differen membrane functions?

Answer 3

Protect cell
Compartmentalise cell
Control movement of molecules
Transmit signals
Cell recognition
Communication with surrounding cells

Question 4

Describe the role of cholestrol in the membrane

Answer 4

Maintain fluidity

Question 5

Describe the function of carbs in the membrane and the 3 classes of lipids

Answer 5

Binds to lipids/proteins for communication/signalling

Phosphoglycerides, Sphingolipids, Sterols (eg Cholesterol)

Question 6

Describe the phospholipid structure

Answer 6

It’s amphipathic - Has both hydrophilic and phobic parts

Question 7

Describe sterols

Answer 7

Smaller than other membrane lipids
Single polar head attached to steroid ring and short non
polar tail
Common in EK cells not PK

Question 8

What are the factors affecting fluidity

Answer 8

Saturation
Temperature
Cholesterol

Question 9

Describe the effect of temperature on the membrane

Answer 9

Low temp - Low energy fluidity low (*If phospholipids so close = Crystalised)
Warm temp - More energy/more distance/more fluidity

Question 10

Describe the effect of cholesterol on the membrane

Answer 10

Acts as temp buffer
In cold temp, keep phospholipids apart - Increasing fluidity
In warm temp, chol binds to lipids tighter - Decreasing fluidity

Question 11

Give an example of the effect of cholesterol on the membrane

Answer 11

RBC plasma membrane has high number of cholesterol due to various temp changes across the body to give o2 at a constant rate and also to keep its biconcave shape

Question 12

Describe lipid rafts

Answer 12

Have high conc of cholesterol and glycosphinogolipids
Organise plasma membranes into groups
Involved in cell movement and signalling

Question 13

What are the different types of membrane proteins and name an example?

Answer 13

Peripheral proteins - Glycoprotein
Integral proteins - Span across entire protein
Membrane bound proteins

Question 14

Name an example of transport proteins

Answer 14

Channel/ Carrier proteins

Question 15

Describe the movement of phospholipids laterally

Answer 15

Frequent, little energy needed

Question 16

Describe the movement of phospholipids across the membrane

Answer 16

Slow without catalyst
Cat. Flipase - Moves phos out to in
Cat. Floppase - Moves phos in to out
Cat. Scramblase flip flop at same time
Energy via ATP provided