Structure of the Cell Membranes Flashcards
What is the phospholipid head hydrophobic or hydrophilic?
Hydrophillic
Is the phospholipid tail hydrophobic or hydrophillic?
Hydrophobic
What is the phospholipid bilayer?
Two phospholipid molecules together with the heads facing out and the tails facing in.
What does it mean if the phospholipid head is hydrophilic?
The head is attracted to water
What does it mean if the phospholipid head is hydrophobic?
It is repelled by water
What are the functions of the phospholipid bilayer?
- Allow lipid soluble substances to enter and leave the cell.
- Prevent water soluble molecules from entering/leaving the cell.
- Makes the membrane flexible and self sealing.
What do protein channels do?
Allow water-soluble molecules to diffuse across the membrane.
How do carrier proteins work?
Bind to ions/molecules then change shape to move these molecules across the membrane.
Which proteins do you find on the cell-surface membrane?
- Structural proteins
- Channel proteins
- Carrier proteins
- Cell surface receptors
What does cholesterol do when it is in the cell-surface membrane?
- Add strength to the membrane making it less fluid at high temperatures.
- Limit movement of phospholipids and other molecules by pulling the fatty acid tails together. (Still doesn’t make it too rigid).
- Cholesterol is very hydrophobic, preventing the leakage of water and dissolved ions from the cell.
What does cholesterol allow the CSM to do when at high temperatures?
Stay less fluid
How does cholesterol limit movement of phospholipids and other molecules?
Pull together the fatty acid tails of the phospholipid molecules.
How does cholesterol prevent the leakage of water and dissolved ions from the cell?
As cholesterol is very hydrophobic
What are glycolipids made of?
Carbohydrates covalently bonded with a lipid.
What are the functions of glycolipids?
- Act as recognition sites
- Maintains stability of the membrane
- Helps cells to attach to each other to form tissues.
How do glycoproteins act as recognition sites?
The carbohydrate part extends outside the cell to act as a cell-surface receptor for specific chemicals.
What are glycoproteins?
Carbohydrate chains which extend from many extrinsic proteins on the outer surface of the cell membrane.
What are the functions of glycoproteins?
- Act as recognition sites, specifically for hormones and neurotransmitters.
- Help cells attach to one another to form tissues.
- Allows cells to recognise each other.
Which molecules can’t pass through the cell-surface membrane?
- Molecules which are insoluble in lipids.
- Molecules which are too large to diffuse through the membrane and too large to diffuse through the protein channels.
- Molecules which have the same charge as the protein molecules as they are repelled.
- Polar molecules due to the non-polar tails in the phospholipid bilayer.
What is the fluid-mosaic model of the cell surface membrane?
The way in which all the various proteins combine into the structure of the cell-surface membrane.
What does the “fluid” part of the fluid-mosaic model mean?
As the individual phospholipid molecules can move relative to one another, giving the membrane a flexible structure.
What does the “mosaic” part of the fluid-mosaic model mean?
The proteins embedded in the phospholipid bilayer vary in shape, size and pattern.
What are extrinsic proteins?
Proteins on the outside of the CSM
What are intrinsic proteins?
Proteins inside the CSM.
