Cell surface membrane Flashcards
Describe cholesterol and its role (in cell membranes)
- embedded in the bilayer
- acts as a buffer for membrane fluidity. (at high temperatures prevents fluidity from rising too high, and at low temperatures, prevents membrane becoming solid)
- prevent leakage of water
- reduce lateral movement of other molecules
What are 2 types of proteins found in cell membranes?
- integral; span the whole of the membrane (e.g transport proteins)
- extrinsic; only one side of the bilayer
(give support or act with glycolipids as cell receptors)
What are 6 functions of proteins in cell-surface membranes?
- structural support
- protein channels; transport water soluble substances
- allow active transport; through carrier proteins
- form cell-surface receptors for identifying cells
- help cells adhere together
- act as receptors
What are 3 functions of glycolipids in cell membranes?
- recognition sites
- maintain stability
- help cells attach to each other
What are the functions of phospholipids in cell-surface membranes?
- Lipid soluble substances to pass through
- Flexibility and self-sealing
- Stop water soluble substance entering and leaving cells
Describe the bilayer
formed from two layers of phospholipids. These molecules have hydrophilic heads which face out of the bilayer and hydrophobic tails which face into the bilayer, so they don’t come in to contact with water .
Why is the structure of cell membranes called the fluid mosaic model?
fluid- as the phospholipids allow movement
mosaic- as it is made up of many different components
How does temperature impact cell surface membranes?
an increase in temperature increases the fluidity of the membrane, as a result increasing it’s permeability
How does pH impact cell surface membranes?
it impacts the protein structure of the proteins in the cell membrane
How does solute concentration impact cell surface membranes?
Phsopholipid bilayer is dissolved more easily, increasing its permeability
How does colour indicate the permeability of membranes when investigating using beetroot?
The darker the solution of beetroot, the more pigment has been released because the membrane is more permeable. A darker solution will have a higher reading for absorbance
Why is fluidity an important characteristic of cell membranes?
It allows flexibility for the cell, increased motion needed in transport
What is a glycolipid?
phospholipid with a carbohydrate chain attached
What is a glycoprotein?
a protein with a carbohydrate group attached
