2.1.5 Biological membranes Flashcards
What is compartmentalisation?
Formation of separate membrane bound organelles
Why is compartmentalisation needed?
Allows for specific conditions such as chemical gradients to be maintained as reactions are contained to specific parts
Explain the fluid mosaic structure
- Phospholipids free to move giving membrane flexibility
- Proteins embedded in a random arrangement
What are intrinsic proteins? Give examples
- Proteins embedded in both layers of membrane
- Hydrophobic R-groups to interact with hydrophobic core
- E.g. carrier and channel proteins
What type of transport do channel proteins allow?
Passive transport of polar molecules
What type of transport do carrier proteins allow?
Active and passive transport which often involves shape of protein changing
What are glycoproteins?
- Proteins with attached carbohydrate chain
- Role in cell signalling e.g. neurotransmitters or peptide hormones
What are glycolipids?
- Lipid with attached carbohydrate chain
- Role in cell signalling e.g. antigens in immune system
What are extrinsic proteins?
- Proteins embedded in one side of the membrane
- Hydrophilic R-groups to interact with hydrophilic heads
- E.g. glycolipid or enzymes
What is the role of cholesterol in the phospholipid bilayer?
- Binds to phosphate heads
- Increases packing
- Reduces fluidity
What happens to phospholipid bilayer when temperature is increased?
- More kinetic energy
- More fluid membrane
- Increased permeability
- Carrier and channel proteins denatured
What happens to phospholipid bilayer when solvent is added?
- Less polar solvent will dissolve membrane
- More fluid
- More permeable
What is needed for facilitated diffusion?
Channel proteins
What type of molecule can pass through he membrane via simple diffusion?
Non-polar molecules with no charges
(Polar water can pass through but verryyyy slowly)
A greater SA:V ratio means a _____ rate of diffusion
Greater
