Chapter 5 - Biological Membranes Flashcards
Roles of membranes within cells
- selective permeability
- surface for enzyme attachment
- form vesicles
- compartmentalisation
- create concentration gradients
Roles of membranes at cell surfaces
- Plasma membranes are partially permeable
- Create barriers to substances
- cell recognition and signalling
Three. Intrinsic proteins.
Carrier channel, Glyco
Channel proteins
Diffusion of polar molecules or ions through membranes
Carrier proteins
Active transport of molecules into cells
Glycoproteins
Cell adhesion and receptors for cell signalling
Glycolipids
Cell markers, or antigen is to be recognised by the immune system
Cholesterol
Regulates membrane, fluidity and stability by preventing phospholipids, grouping and crystallising
What factors affect membrane permeability
Solvent and temperature
How to solvents affect membrane permeability
Organic solvents, dissolve membranes and disrupt cells creating gaps in membranes, which increases fluidity and permeability
How does temperature affect membrane permeability
Increasing temperature increases, kinetic energy of phospholipids increases fluidity, so the membrane loses structure
The effect of extreme temperatures on membrane permeability
Membrane breaks down completely channel, proteins, denature, so transport is limited
Define diffusion
The net movement of particles down a concentration gradient
What factors affect the rate of diffusion?
Temperature
concentration difference,
surface area
membrane thickness
Simple diffusion
Diffusion across a membrane without using channel proteins
