CH5 membranes Flashcards
What are membranes
Structures that seperate the contents of cells from their environment
What is compartmentalisation
The formation of seperate membrane-bound areas within a cell
Why is compartmentalisation important
Metabolism includes many different and often incompatible reactions
What is the plasma membrane
The cell surface membrane that seperate cell from external environment
What are membranes formed of
Phospholipid bilayer
Why is a phospholipid bilayer suited to function
As the outer part is hydrophilic so is able to interact with water
When were membranes first seen
- 1950
- shown as two parallel black lines
What model was proposed in 1972
Fluid mosaic model where phospholipids are free to move within membrane relative to eachother
What is an intrinsic protein
Proteins that are embedded through both layers of the membrane
How are intrinsic proteins held in place
They have amino acids with hydrophobic r groups on external surface which interact with hydrophobic core of membrane
What are channel proteins
- Intrinsic protein
- provide a hydrophilic channel that allows passive movement of polar molecules
What are carrier proteins
- Intrinsic protein
- have role in active and passive transport
What are glycoproteins
- Intrinsic protein
- have an attached carbohydrate chain
- plays a role in cell adhesion and as a receptor of chemical signals
What are glycolipids
- Lipids with an attached carbohydrate chain
- cell markers as recognised by cells of immune system
What is an extrinsic protein
Proteins present on one side of the bilayer
How are extrinsic proteins held in place
Have amino acids with hydrophilic r groups on the surfaces and interact with polar heads of phospholipids or intrinsic proteins
How is cholesterol held in place
Hydrophilic end interacts with phosphate heads and hydrophobic end interacts with fatty acid core
How does temperature affect membrane structure
- Increased temperature means phospholipids have more kinetic energy and move more which makes membrane more fluid
- Loss of structure increases permeability
- Proteins can be denatured
How does solvent affect membrane structure
Organic solvents dissolve membranes and disrupt cells
