what is the structure of the membrane called?
the fluid mosaic model
why is the cell membrane described as fluid and mosaic?
- fluid because the sea phospholipids have the ability to move
- mosaic as it contains a variety of different molecules
what molecules are found within the cell membrane?
- phospholipids
- exterior proteins
- interior proteins
- cholesterol
- glycolipids
- glycoproteins
Describe the structure of phospholipids.
- hydrophilic, polar, phosphate head
- hydrophobic, non-polar, fatty acid tail
- tail faces inward (creates bilayer) and heads facing outwards
how does the structure of phospholipids affect the cell membrane?
- means that only small, non-polar lipid soluble molecules to pass through the membrane via diffusion
- means that the membrane is fluid/flexible
what are extrinsic proteins (with examples)?
1.proteins on the surface of the membrane
2. enzymes
what is an intrinsic protein (with examples)?
- proteins that go all the way through the cell membrane
- carrier and channel proteins
what is the function of extrinsic protein?
- enzymes catalyse chemical reactions
- they act as receptor
- act as structural support
what is the function of intrinsic proteins?
- carrier proteins allow molecules to pass through via active transport and facilitated diffusion
- channel proteins allow polar, large, water soluble molecules into the cell
- aquaporins allow water to entre the cell (osmosis)
what are glycoproteins?
they are carbohydrates attached to extrinsic proteins
what is the function of glycoproteins?
they act as a neurotransmitter and receptor as they allow cells to be recognised by each other and attach to form tissue
what is a glycolipid?
carbohydrates bound to lipids
what is the function of a glycolipid?
- extends from the cell surface acting like a receptor
- allows cells to form tissues
what is the function of cholesterol?
- it makes it more rigid which reduces lateral movement
- prevents leakage of water and dissolved ions as it’s very hydrophobic
