biological membranes

Question 1

cell membranes are partially permeable. what does this mean?

Answer 1

needs to allow some molecules through, into or out of the cell. Does not let all types of molecule through.

Question 2

3 ways molecules + substances go through the partially permeable membrane

Answer 2

• some small molecules diffuse through the cell, in between its structural molecules
• some substances dissolve in the lipid layer + pass through
• pass through special protein channels or carried by carrier proteins

Question 3

4 roles of the membrane at the surface of cells

Answer 3

• separates cell’s components from external environment
• allows cell communication / cell signalling - contains receptors for chemical signals
• allow recognition by other cells
• regulates transport of materials in + out of the cell.

Question 4

3 roles of the membrane with cells

Answer 4

• compartmentalisation = separation of different parts of the cell with different functions
• site of chemical reactions
• can form vesicles too transport substances between different areas of the cell.

Question 5

why is the bilayer ‘fluid’

Answer 5

the phospholipids are constantly moving

Question 6

what year was the fluid mosaic model proposed

Answer 6

1972

Question 7

how thick is the phospholipid bilayer

Answer 7

7nm

Question 8

what do intracellular membranes form

Answer 8

compartments with the cell, such as organelles

Question 9

what does the fluid mosaic model explain

Answer 9

how molecules are arranged to form cell membranes.
- passive and active movement between cells and their surroundings
- cell-to-cell interactions
- cell signalling