Cell membrane structure Flashcards
1
Q
What are plasma membranes made of?
A
- A double layer of phospholipids- bilayer
- Contains proteins, cholesterol, glycoproteins, and glycolipids
2
Q
What is the structure of a phospholipid?
A
- 1 phosphate group- hydrophilic
- 1 glycerol
- 2 fatty acids- hydrophobic
3
Q
How do phospholipids arrange themselves in water?
A
- Hydrophilic heads face outwards towards water
- Hydrophobic tails face inwards away from water
4
Q
What is diffusion?
A
- Net movement of particles from high to low concentration
- Moves down a concentration gradient
- Passive process
5
Q
What molecules can diffuse directly through the bilayer?
A
- Non-polar
- Uncharged molecules
- Small polar molecules
6
Q
What molecules cannot diffuse through the bilayer?
A
- Large polar molecules and ions
- They are rejected by the hydrophobic fatty acid tails
7
Q
How do charged ions pass through the membrane?
A
- Through ion channel proteins
- Bind to a specific binding site
- Move down their concentration gradient- facilitated diffusion
8
Q
What is facilitated diffusion?
A
- Passive process
- Moves molecules down a concentration gradient
- Uses channel proteins or carrier proteins
9
Q
How do carrier proteins work in facilitated diffusion?
A
- Molecule binds to carrier protein
- Carrier protein changes shape
- Molecule is released on the other side
10
Q
What are intrinsic proteins?
A
- Span the entire bilayer
- Hydrophobic R groups face outwards
- Hydrophilic R groups face inwards- allow diffusion of molecules
11
Q
What are the functions of membrane proteins?
A
- Glycoproteins: Cell recognition, communication, tissue formation
- Extrinsic proteins: Act as receptors for hormones or messengers
- Channel proteins: Facilitate diffusion of charged ions
- Carrier proteins: Transport molecules across the membrane
12
Q
What is the function of cholesterol in the membrane?
A
- Sits between phospholipid tails
- Maintains stability and fluidity of the membrane
- Prevents the membrane from becoming too rigid or too fluid
- Prevents crystallization at cold temperatures
- Holds fatty acid tails together at warm temperatures
13
Q
What increases membrane fluidity at low temperatures?
A
- Double bonds between carbon atoms in fatty acid chains
- Shorter fatty acid chains
14
Q
What is the fluid mosaic model?
A
- Fluid: Phospholipids and proteins move within the bilayer
- Mosaic: Scattered proteins form a pattern
15
Q
Why is it called the fluid mosaic model?
A
- Phospholipids move within the membrane
- Contains different types of proteins (e.g., glycoproteins, carriers, channels)
- Based on experimental evidence
