Medical Physics Wk 1

Question 1

Describe the structure of phospholipids

Answer 1

The polar head groups face the water and the hydrocarbon fatty acid tails face the hydrophobic core

Question 2

What is the function of the lipid bilayer

Answer 2

Serves as a selective permeability barrier separating cellular compartments and the inside from the outside

Question 3

What is cholesterol and what is its function

Answer 3

It intercalates between the phospholipids with its hydroxyl group near the polar head groups and its steroid ring parallel to the fatty acid chains of the phospholipids and perpendicular to the membrane surfaces and modulates the membrane phospholipid structure

FUNCTION:
Restricts movement of phospholipids- reduces membrane fluidity
Disrupts regular packing of hydrocarbon chains - increases flexibility
Reduces permeability of membranes to hydrophilic, water soluble molecules - ions of sodium, hydrogen
Reduces the segregation of different phospholipids- makes membrane lipid composition more heterogenous

Question 4

Describe how membranes undergo continuous turnover

Answer 4

The breakdown and reassembly may be important for structural rearrangements or maybe induced as a repair process.

For example, endocytosis or exocytosis processes that involve fusion and processes of membranes that affect the structure of cellular plasma membranes