3 TAM - Factors affecting membranes Flashcards
What are the main factors affecting membrane permeability?
- Solvents
- Temperature
How do solvents affect membrane permeability?
- NON-POLAR solvents can insert themselves into the bilayer, forming H bonds with phospholipids near the ester bonds
- This results in the displacement of the usual order of the phospholipid bilayer and can denature channel + carrier proteins
- Overall = this increases membrane permeability
- (this is how alcohol breakes down bacterial cell membranes, killing them)
How does a temperature of below 0°c affect membrane permeability?
- Phospholipids packed closely together, makes membrane rigid
- Channel + carrier proteins = denatured (increases permeability)
- Ice crystals form, these pierce the membrane and cause permeability to increase when the cell is thawed.
Hoe does a temperature of 0°c - 45°c affect a membrane?
- Phospholipids move around freely, keeping to gel like consistency and holding as a bilayer
- As kinetic energy increases so does membrane permeability
How does a temperature of above 45°c affect membrane permeability?
- Phospholipids begin to melt
- Water inside the cell expands, exerting more pressure on the cell membrane
- Channel + carrier proteins denature
- Overall = membrane permeability increases
What is the experiment that can be done to prove that membrane permeability increases due to certain factors?
Beetroot cells contain a pigment in the cell vacuole, betalains, when cooked, betalains escape the cells due to the increased membrane permeability as the phospholipids have increased kinetic energy.
How does a colourimeter work?
Machine passes light of a specific wavelegnth through a sample and the amount of light received on the other side of the sample is recorded, the more concentrated a solution is, more light is absorbed by it.
How is a colourimeter calibrated?
- solutions of a known concentration are used to create a graph in order to test solutions of an unknown concentration
