Plasma Membranes Flashcards
Name 3 membrane-bound organelles
- mitochondria
- chloroplasts
- vacuole
What is the lipid bilayer composed of?
Phospholipids with cholesterol bedded inside
What is the structure of a phospholipid?
- Phosphate head
- Glycerol
- Fatty acid tails
Why do the phospholipids form a bilayer?
Because the phosphate heads are hydrophilic (water-loving), they go on the outside whereas the fatty acid tails are hydrophobic (water-hating) go on the inside. The phosphates form a barrier around the fatty acid tails.
What does the bilayer do?
- Gives the membrane flexibility
- Allows lipid soluble substances to enter and leave the cell
What else is in a cell membrane?
Proteins
What are the two types of protein
Extrinsic and Intrinsic
Define extrinsic proteins
Loosely bound proteins on the outside of a membrane. Also known as peripheral proteins.
Define intrinsic proteins
Embedded in a membrane. They may be partially embedded, or span the membrane.
What role do extrinsic proteins perform?
- Transport molecules through the bilayer
- Act as receptors for hormones
- Some are enzymes
What role do intrinsic proteins perform?
- Transport molecules through the bilayer
- Some are enzymes
What is the effect of ethanol on plasma membraes?
The phospholipids dissolve in it as it is a non-polar substance
What is the role of cholesterol?
Cholesterol gives the membrane stability by stopping fatty acid tails sticking together
What are the roles of glycoproteins and what is it?
A carbohydrate polymer
Used for adhesion and as antigens (for example T cells)
What are the roles of glycolipids and what is it?
A carbohydrate polymer
Used for cell recognition and antibodies
