Week 1b: Cell Membrane

Question 1

Where is cell membrane found?

Answer 1

Around the outside of all living cells.

Question 2

What does the cell membrane do?

Answer 2

Controls the movement of substances into and out of the cell.

Question 3

What does FLUID in the ‘fluid mosaic model’ refer to?

Answer 3

• The ability of both the lipids and proteins to move laterally (sideways) within the membrane structure)
• The membrane relies on it’s fluid nature to carry out it’s functions.

Question 4

What does MOSAIC in the ‘fluid mosaic model’ refer to?

Answer 4

The variety of protein molecules attached/embedded in the phospholipid bilayer

Question 5

What is contained in the cell membrane? (5)

Answer 5

• Two layers of phospholipid molecules
• Two kinds of membrane proteins
• Cholesterol
• Glycoproteins
• Glycolipids

Question 6

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

Answer 6

Integral proteins: permanently in the bilayer

Peripheral proteins: tend to move temporarily and are not a permanent part of the membrane

Question 7

In which type of cell is cholesterol present?

Answer 7

Animal cells

Question 8

Where is cholesterol positioned within the cell membrane?

Answer 8

Between the phospholipids

Question 9

What are glycoproteins?

Answer 9

Membrane proteins with carbohydrate chains attached

Question 10

What are glycolipids?

Answer 10

Phospholipids with carbohydrate chains attached

Question 11

What are the structural characteristics of the cell membrane? (4)

Answer 11

• Very thin
• Fluid-mosaic
• Two layers of phospholipids
• Proteins molecules embedded or attached

Question 12

What are the functional characteristics of the cell membrane (4)

Answer 12

• Separate contents of cell from external environment
• Regulate passage of substances in/out of the cell
• Cell recognition (eg: other cells and hormones)
• Enable attachment of cytoskeleton

Question 13

What does ‘hydrophobic’ mean?

Answer 13

Does not dissolve in water (non-polar lipid)

Question 14

What does ‘hydrophillic’ mean?

Answer 14

Does dissolve in water (polar phosphate group)

Question 15

What are channel proteins?

Answer 15

Proteins which either allow movement of molecules by diffusion, or use energy to ACTIVELY move molecules in and out of cells.

Question 16

In the cell membrane, what is the purpose of cholesterol?

Answer 16

Cholesterol regulates the fluid nature of the phospholipids. The cell membrane separates the cell from its surroundings and controls the exchange of nutrients and wastes in and out of the cell.

Question 17

Proteins involved in cell communication:

Answer 17

Receptor proteins - cell communication can occur via direct contact between cell membrane proteins of adjacent cells or via hormones or neurotransmitters.

Question 18

Proteins involved with cell adhesion -

Answer 18

Integral proteins can stick out and bind to specific protein molecules on adjacent cells or attach to the cytoskeleton.

Question 19

What is the cytoskeleton?

Answer 19

A framework of tiny protein tubules and filaments that extends throughout the cytosol. Its function includes attachment and movement of organelles, and movements of the cell membrane and chromosomes.