Lecture 17: Membrane lipids and their proteins Flashcards
What are the functions of membrane proteins?
- Cell-cell contact
- Surface recognition
- Cytoskeleton contact
- Enzymes
- Transporters
- Receptors and signallign - signal transduction
How do membrane proteins interact with membranes?
- how are they situated in the membrane?
- Span the protein = involved in signal transduction
- Embedded in the membrane
- On the surface of the membrane
- Partially inserted into the membrane
What is membrane fluidity affected by?
- Temperature
- Type of fatty acid
- Presence of cholesterol
How does cholesterol affect membrane fluidity?
Cholesterol helps stiffen the membrane
- At high temperatures cholesterol reduces the fluidity
- At low temperatures cholesterol increases the fluidity as it stops if from packing together
How does the type of fatty acid affect membrane fluidity?
SATURATED tails pack together decreasing the fluidity = membrane is stiffer
UNSATURATED tails prevent packing together and increase the fluidity
The LONGER the chain is the more hydrophobic interactions so less fluid and more rigid
Why is compartmentation of cells by membranes important?
Creates compartment –> so specific processes can occur
- provide special conditions for specific processes
- keeps incompatible process apart
What are amphipathic molecules ?
Are molecules which form bilayers in aqueous environments
- both have polar head group and hydrophobic tails which interact with water and the lipid tails pack together
- Hydrophobic hydrocarbon trials are 16-22 carbon long fatty acids
- Saturated = No double bonds
- Unsaturated = Yes double bonds - introduces a kink and result in increased membrane fluidity
What do phosphate lipids consist of?
Consist of glycerol linked by ester bonds to two fatty acids, with the remaining glycerol hydroxyl linked to a phosphate
