The Cell Surface

Question 1

Properties of phospholipids

Answer 1

Hydrophilic head - glycerol, phosphate, head group

Hydrophobic tail - fatty acid chains

Question 2

How does cholesterol affect membranes?

Answer 2

• Inserted between the membrane phospholipids
• Add rigidity by stabilising interactions between phospholipids so therefore effect membrane fluidity
• Makes membranes less permeable

Question 3

3 reasons why membranes being fluid structures is important

Answer 3

• allows signalling lipids and membrane proteins to diffuse in the lateral plane and interact with one another
• allows membranes to fuse, e.g. exocytosis
• ensures membranes are equally shared between daughter cells following cell division

Question 4

Are the transmembrane regions of proteins hydrophilic or hydrophobic?

Answer 4

• hydrophobic

Question 5

What drives active transport?

Answer 5

The electrochemical gradient