Boundaries and membranes

Question 1

What do cell boundaries allow? (3)

Answer 1

The formation of a semi-fluid matrix for cell functions
The formation of specialised microenvironments where the cell can carry out processes
Segregation of harmful activities

Question 2

What is the size of a plasma membrane?

Answer 2

7nm

Question 3

What are membranes made of?

Answer 3

A lipid bilayer formed of amphipathic lipids. They have a hydrophilic head and hydrophobic tail

Question 4

What is the structure of a amphipathic lipid? (3)

Answer 4

Hydrophilic head: choline and phosphate
Glycerol link
Hydrophobic tail: hydrocarbon tail, one of the 2 has double bond

Question 5

What is the model called that describes the lipid membrane?

Answer 5

Fluid mosaic model

Question 6

What are the lipid anchored membrane proteins used for? (3)

Answer 6

Cell signalling, adhesiveness, communication

Question 7

What are 4 key structural features of the lipid membrane?

Answer 7

Self assembling
They are fluid, can move very quickly
Asymmetry - different compartments and composition
Integral proteins pass through the lipid bilayer

Question 8

Give 3 examples of cell walls

Answer 8

Bacteria have peptidoglycan cell walls for rigidity
Fungi - chitin cell walls for strength
Plants - Cellulose cell walls
Cell walls must have mechanisms for permeability

Question 9

What is the cell cortex?

Answer 9

A framework of proteins under the membrane which is attached to the PM via transmembrane proteins

Question 10

Give 3 examples and functions of extracellular components:

Answer 10

Glycocalyx - cell signalling
Collagen - highly insoluble and forms strong fibres
Partially anchored polysaccharides - recognition