Topic 2 -Cell Membranes Flashcards
What are the functions of phospholipids in the phospholipid bilayer
Cell membranes
it allows lipid soluble substances to pass through but prevents water soluble substances from moving through. It also allows the membrane to be flexible and self sealing.
Describe a cell surface membrane’s permeability
Cell membranes
Its selectively permeable as it allows lipid soluble substances to pass through but prevents water soluble substances from moving through
What’s the model used for cell surface membranes ?
Cell membranes
The fluid mosaic model - its fluid because phospholipids are constantly moving and the size and pattern of the bilayer is mosaic like and proteins are scattered through like a mosiac.
what are extrinsic proteins ?
Cell membranes
Proteins that do not span the whole bilayer, e.g. receptor proteins
What are intrinsic proteins ?
Cell membranes
Proteins that span the whole bilayer, e.g. channel proteins/ carrier proteins
What are channel proteins function ?
Cell membranes
They form pores in the membrane to allow small ions to pass through
What are carrier proteins functions ?
Cell membranes
Bind to larger molecules or ions like glucose and amino acids , then change shape in order to move these across the membrane.
What are the functions of cholesterol in the cell membrane ?
Cell membranes
Adds strength. They’re very hydrophobic so prevent loss of water and dissolved ions from the cell. They fit in between the phospholipids and bind to the tails causing them to pack more closely together, making the membrane more rigid and less fluid by restricting movement. Maintains the shape animal cells (with no cell wall).
What are the functions and structure of glycolipids ?
Cell membranes
Contain a carbohydrate chain covalently bonded with a lipid. This acts as a cell surface receptor for chemical. They help maintain the stability of the membrane. They act as recognition sites. Help cells attach to each other to form tissues.
What’s the function and structure of glycoproteins ?
Cell membranes
Carbohydrate chains attached to extrinsic proteins covalently. Thy act as cell surface receptors, more specifically for hormones and neurotransmitters. They act as recognition sites, help cells attach to form tissues, and allow cells to recognise each other
What happens to a cell surface membranes permeability in temperatures below 0 degrees ?
Cell membranes
Phospholipidss dont have much kinetc enegery so they cn’t move very much, they’re packed cloely together making the membrane rigid. Channel and carrier proteins deform, increasing permeability. Ice crystals may form and peirce the membrane, making permeability increase when it thaws.
What happens to a cell surface membranes permeability in temperatures between 0 and 45 degrees ?
Cell membranes
Phospholipids can move around more as they aren’t packed as closely together-the membrane is partially permeable. As temperature increases, the phospholipids move more as they’re given more energy. This increases the permeability of the membrane.
What happens to a cell surface membranes permeability in temperatures above 45 degrees ?
Cell membranes
The phospholipid bilayer begins to melt and the membrane becomes permeable. Water in the cell expands, putting pressure on the membrane. Channel and carrier proteins deform-they cannot control what enters of exits the cell so the permability increases.
How would you investigate the permability of beetroot at different temperatures ?
Cell membranes
- use a scapel to cut 5 identical peicies of beetroot and rinse them.
- Place them each in their own test tube with 5cm3 of water (using a measuring cylinder).
- Place each test tube in a different water bath of doffernt temperaures (10,20,30,40 and 50 degrees) for 20 minutes (using a stopwatch).
- Remove the beetroot.
- Use a colorimeter - a machine that passes light thorugh liquid and measures how much light is aborped, the more absorption, the more pigment, the more permeable the membrane.
- connect the colorimetre to a computer to collect the data.
What’s the definnitoin of diffusion ?
Cell membranes
The net movement of molecules or ions from an area of higher concentration to an area of lower concentation down the concentration graident.