1
Q
Necessity of movement of substances across a plasma membrane (2)
A
- carry out living processes
- metabolic processes in cells produce waste that need to be disposed
2
Q
Structure of plasma membrane (6)
A
- phospholipid bilayer
- channel protein
- carrier protein
- cholesterol
- glycoprotein
- glycolipid
3
Q
Phospholipid bilayer structure (4)
A
- polar head which is hydrophilic (attracted to water)
- nonpolar tail which is hydrophobic (repels water)
- heads in outer layer face extracellular fluid whereas head in inner layer faces cytoplasm
- tails of the phospholipid molecule of the 2 layers face each other
4
Q
Protein molecules (2)
A
- channel protein (has channels/canals)
- carrier protein (functions as carrier)
5
Q
Glycoprotein & Glycolipid functions (3)
A
- act as receptors to hormones (insulin)
- stabilise the membrane by forming hydrogen bonds with water
- act as antigens for cell identification
6
Q
Cholesterols location & functions (3)
A
- found between phospholipid molecules make phospholipid bilayer: - stronger - more flexible - less permeable to water-soluble substances (ions)
7
Q
What contributes to the ‘fluid’ characteristic of the plasma membrane? (2)
A
- phospholipid bilayer, protein & cholesterols are not static but form a dynamic & flexible structure
- makes the plasma membrane more flexible
8
Q
What does a permeable membrane mean?
A
- membrane that allows the substances to pass through it freely
9
Q
What does an impermeable membrane mean?
A
- A membrane is impermeable if a substance is unable to move across it.
10
Q
The plasma membrane is selectively permeable. What does selectively permeable mean?
A
- Selectively permeable membrane only allows free movement of certain molecules across it, & prevent or limit the movement of other substances
11
Q
Why does the plasma membrane have a selectively permeable membrane? (2)
A
- due to its building structure
- phospholipid bilayer and protein determine the membrane permeability towards specific substances
