2.5 Flashcards
What is the role of membranes on the cell surface?
Plasma membrane
Regulates the movement of materials in and out the cell
Maybe the site of chemical reactions
Separate the cell’s components from the external environment
What is the role is membranes within a cell?
Separate the organelle contents from the cell cytoplasm
Describe the fluid mosaic model
It was suggested that the fabric of the membrane consisted of a phospholipid bilayer made of fluid.
It had protein molecules scattered across the bilayer as well as cholesterol within the bilayer
What is the role of phospholipids?
Form a barrier to dissolved substances as it has a hydrophilic head and hydrophobic tail which doesn’t allow water soluble substances through
What is the role of cholesterol?
Gives the membrane stability by making it less fluid and more rigid
What is the role of proteins?
Controls what enters and leaves the cell
What is the role of glycolipids and glycoproteins?
Acts as receptors for messenger molecules as well as stabilise the membrane by forming hydrogen bonds with surrounding water molecules
What two factors affect the permeability of membranes?
Temperature
And
Solvent used
How does temperature affect membrane permeability?
Increasing the temperature increase membrane permeability
0C - not enough energy for phospholipids to move
0-45C - phospholipid can move and membrane is partially permeable as temp increase as does permeability
Above 45C - phospholipid bilayer starts to melt and membrane becomes more permeable
How does a solvent affect membrane permeability?
Different solvents and concentrations can affect the permeability
Increasing the concentration of a solvent will increase the permeability
