Cell Membrane Structure

Question 1

What is the currently accepted model of the cell membrane?

Answer 1

The fluid mosaic model, proposed by Singer and Nicolson in 1972.

Question 2

Describe a phospholipid molecule.

Answer 2

Has a hydrophilic phosphate head, which will face the internal and external environment of the cell. Has two hydrophobic, fatty acid tails. Glycerol connects the two components. The molecules can move past each other but not vertically.

Question 3

Describe what happens when phospholipids make a bilayer, such as in the cell membrane.

Answer 3

The water attracting heads are positioned facing outwards, and the water repelling tails face inwards. This occurs due to the molecules’ emergent property, where they self organise in water.

Question 4

Describe the position of proteins the cell membrane.

Answer 4

Protein molecules are dispersed and embedded in the membrane. Some penetrate all the way through the layer, while others are partly embedded.

Question 5

Describe the role of glycoproteins in the cell membrane

Answer 5

They are proteins that allow cell recognition in immune system and hormones.

Question 6

Describe the role of transport proteins in the cell membrane

Answer 6

Act as passage ways to allow specific substances to move across the membrane

Question 7

Identify some other functions of proteins in the cell membrane.

Answer 7

receptors, anchorage, intercellular joining, enzymatic activity.

Question 8

What is the role of cholesterol molecules in the cell membrane?

Answer 8

Makes the phospholipids pack more tightly, decreases fluidity, increases flexibility and reduces permeability to water soluble molecules.