Membranes

Question 1

Roles of membranes within cells and at the surface of cells?

Answer 1

Plasma membranes:
Seperates cell contents from outside environment
Controls the passage of materials in and out of the cell
Recognition of other cells
Receptor sites for signalling molecules
Transmission of nerve impulses
Insulation of nerves

Inside cells:
Acts as a reaction surface
Acts as an intracellular transport system
Compartmentalises cells, isolating different chemical reactions
Can form vesicles to transport substances
Isolate potentially harmful enzymes eg. in lysosomes

Question 2

What is compartmentalisation?

Answer 2

The formation of cellular compartments

Question 3

Why is compartmentalisation useful?

Answer 3

Different processes require different environments, eg ph

Provides extra membrane surface area for reactions

Question 4

What is a partially permeable membrane?

Answer 4

Membrane which allows the passage of small molecules of water and certain solutes, but not large solute molecules

Question 5

What is cell signalling?

Answer 5

Processes that lead to communication and coordination between cells. Hormones binding to their receptors is an example

Question 6

What’s a phospholipid bilayer?

Answer 6

Glycerol bonded to 2 fatty acids and a phosphate (phospholipid), bonded in a 2 layer arrangement, phospholipid heads in at edges (hydrophilic), tails at centre (hydrophobic)

Question 7

What is meant by “fluid”, and “mosaic” in the fluid mosaic model?

Answer 7

Fluid= how some parts of the membrane can move around freely

Mosaic describes the patchwork of proteins in the membrane