The Cell Surface Membrane

Question 1

What is the role of membranes?

Answer 1

-creates an enclosed space separating internal cell environment from external environment
-siteof chemical reactions

Question 2

What do intracellular membranes do?

Answer 2

-form compartments within the cell + vacuoles
-control exchange of materials passing through
-substances cross by diffusion, facilitated, osmosis and active transport

Question 3

What is the fluid mosaic model of membranes?

Answer 3

-all cells + organelles are surrounded by a partially permeable membrane composed of a sea of phospholipids
-phospholipids mainly move sideways - in their own layers
-diff types of proteins interspersed throughout the bilayer

Question 4

What are phospholipids?

Answer 4

-form basic structure of the membrane
-tail = hydrophobic
-bilayer acts as barrier to soluble substances
-non-polar acid tails prevent polar ions passing through
-sugars + amino acids can’t leak out

Question 5

What does cholesterol do?

Answer 5

-increases fluidity of the membrane
-occurs as it stops phospho tails packing too closely together
-stabilises from becoming too liquid
-increases strength + stability

Question 6

What are glycolipids and glycoproteins?

Answer 6

-contains carb chains - on surface - act as receptor molecules
-bind with certain substances at surface
-act as cell markers or antigens for cell to cell recognition

Question 7

What are the 3 types of receptors?

Answer 7

-signalling for hormones
-endocytosis
-adhesion and stabilisation

Question 8

What are transport proteins?

Answer 8

-create hydrophilic channels to allow ions + polar molecules to travel through membrane

Question 9

What are the 2 types of transport proteins?

Answer 9

-carrier + channel
-carrier - change shape to transport substances