Plasma Membranes Flashcards
1
Q
Functions of membranes? (5)
A
- Keeps components inside
- Selected molecules can move in and out
- Isolating organelles
- Site for reactions
- Allows a change in cell shape
2
Q
How does the phospholipid bilayer work? (2)
A
- Hydrophilic heads make outer and inner lining to interact with aqueous surroundings
- Double layer (bilayer)
3
Q
What are intrinsic proteins? (4)
A
- Embedded in the membrane
- Amino acids with hydrophobic R-Groups
- On external surfaces
- Interacts to hydrophobic cores
4
Q
What are channel proteins? (2)
A
- Hydrophilic channel
- Passive movement of polar molecules
5
Q
What are carrier proteins? (2)
A
- Passive and active transport
- Involves the shape of the proteins changing
6
Q
What are glycolipids? (2)
A
- Lipids with attached carbohydrate
- Cell markers - recognised by immune system
7
Q
What are extrinsic proteins? (3)
A
- Hydrophilic R-Group
- Interact with polar head of bilayer
- Can be present in both layers and some can move between layers
8
Q
What is cholesterol and its function? (5)
A
- Lipid with a hydrophilic end and hydrophobic end
- Positioned between phospholipids in bilayer
- Hydrophobic reacts with tails and hydrophilic interacts with heads (pulls them together)
- Provides stability without making it too rigid
- Prevents membrane from becoming too solid- stopping the phospholipid molecules from grouping too closely and crystallising
9
Q
How does temperature affect membrane structure? (3)
A
- Phospholipids are always moving
- Higher temp. means more kinetic energy so more movement
- Begins to lose its structure and will eventually break down completely if temperature continues to rise
10
Q
How do solvents affect membrane structure? (4)
A
- Water (polar solvent) helps keep the bilayer together
- Alcohols dissolve membrane in bacteria
- As alcohol is nonpolar, it can pass through membrane - causes damage and disruption in the membrane
- Affects neurons in brain when people are intoxicated
