Fluid Mosaic Model

Question 1

What is the function of the plasma membrane?

Answer 1

It defines the borders of cells and most organelles. The plasma membrane is selectively permeable.

Question 2

What does Permeable mean?

Answer 2

This means that the membrane allows some materials to freely enter or leave the cell/organelle while other materials cannot move freely.

Question 3

What is the stucture of Phospholipids?

Answer 3

A phospholipid is a molecule consisting of glycerol, two fatty acids, and a phosphate-linked head group.
The molecules arrange themselves into a bilayer which
The hydrophilic phospholipid head faces outwards and the hydrophobic fatty acids faces inwards.

Question 4

What is the role of cholesterol?

Answer 4

Cholesterol is a lipid that sits with phospholipids in the core of the membrane.
Cholesterol molecules make the membrane more rigid. Also, waterproofs the membrane.

Question 5

What factors influence the permeability of cell membranes?

Answer 5

• The more easily the phospholipid bilayer is dissolved, the more permeable the membrane is.
  Solvent concentration can be controlled by using the same solvent at the same concentration for each trial.
• pH affects the protein structure in the cell membrane.
  Buffer solutions can be used to control the pH.
• Higher temperatures increase the fluidity of the membrane, increasing its permeability.
  Using a water bath can help keep temperature constant.

Question 6

What does hydrophilic mean?

Answer 6

This associates with water molecules easily.
Slightly charged, forms hydrogen bonds with water so can dissolve in water.

Question 7

What does hydrophobic mean?

Answer 7

Repels water uncharged, does not from hydrogen bonds with water so cannot dissolve.