U1L8: Fluid Mosaic Model

Question 1

Define the term “Fluid Mosaic Model”

Answer 1

the cell membrane is a “mosaic” of protein molecules bobbing in a fluid phospholipid bilayer

Question 2

What are the two major types of proteins in the cell membrane?

Answer 2

• Integral Membrane Proteins: penetrate far enough into the cell membrane for their hydrophobic regions to be surrounded by hydrophobic tails of phospholipids
• Peripheral Proteins: not embedded in the lipid bilayer. They are appendages attached to the surface of the membrane.

Question 3

Carbohydrates play a role in….

Answer 3

cell-cell recognition (a cell’s ability to distinguish one type of neighbouring cell from another). This is important when sorting cells into tissues and organs during embryo development.
EX: An example of a carbohydrate marker include the four human blood groups (A, B, AB, and O – reflect variation in the oligosaccharides on the surfaces of red blood cells)

Question 4

Cholesterol plays a role in….

Answer 4

adding more stability to to the structure of the membrane. Membranes embedded with more cholesterol are generally firmer at room temperature, but at lower temps, cholesterol molecules break up the packing of phospholipids and makes them more fluid at low temps.

Question 5

Explain the Cell Membrane Function

Answer 5

• The cell membrane is a selectively permeable membrane – this means it allows the passage of some substances through the membrane
• The hydrophobic core of the membrane stops the transport of ions and polar molecules which are hydrophilic. Hydrophobic molecules like oxygen and hydrocarbons can diffuse through the membrane and cross it with ease.
• Very small molecules (like water and carbon dioxide) can also pass through the membrane as they are tiny enough to “shuttle” through the lipids of the membrane

Question 6

How does protein play a part in Cell Membrane Function?

Answer 6

• Cell membrane proteins (e.g. integral proteins) play a role in transporting substances through the membrane