Biological membranes (spec) Flashcards
What are the roles of membranes?
Separate components
Regulate transport
Contain enzymes in metabolic pathways
Antigens for the immune system
Cellular communication - chemical signals
Receptors for chemical signals
Site of chemical reactions
Describe the fluid mosaic model
Phospholipid bilayer with floating proteins
Lipid molecules can change spaces
Proteins move and give fluidity
Phospholipid bilayer creates the main fabric with hydrophilic phosphate head on the outside and hydrophobic fatty acid tail on the outside
What are glycoproteins?
Carbohydrate chain attached to a protein molecule
What are carbohydrates?
Hydrophilic and attract water with dissolved solutes allowing the cell to interact with the environment
What is cholestrol?
Gives mechanical stability and flexibility
What are glycolipids?
Carbohydrates attached to the lipid
What are channel and carrier proteins?
Integral - interact with the hydrophobic regions
Span whole bilayer
How does temperature affect structure and permeability when it drops?
- Fatty acids compress - kinked tails maintain fluidity
- Proportion of saturated to unsaturated fatty acids determines fluidity at cold temperatures
- Cholesterol gives a buffer effect as spaces out phospholipids and stops from becoming too compact
How does temperature affect membrane structure and permeability when it rises?
- Phospholipids have more energy and increases fluidity
- Permeability increases
- Alters position of embedded proteins
- Increases of fluidity can cause infolding of the membrane and change ability to signal
- Cholesterol reduces increase in fluidity
How do solvents affect the structure and permeability of the membrane?
- Organic solvents (acetone and ethanol) damage cell membranes by dissolving lipids
What are the two kinds of passive transport?
Simple and faciliated diffusion
Osmosis
Describe simple diffusion
- Fat soluble and small molecules
- All molecules have kinetic energy
- Move down concentration gradient
- Want equilibrium and no net diffusion
- Pass through gaps in membrane
Describe facilitated diffusion
- Small molecules with polarity (opposite charges at either end of the molecule) - diffuse through pores
- Molecules that are too big (glucose) bind to transmembrane carrier proteins (specific to molecules)
What are the 3 kinds of active transport?
Active transport
Endocytosis
Exocytosis
(they all need ATP)
Describe active transport
- Against concentration gradient
- Needs energy (provided by hydrolysis of ATP)
