Membranes I Flashcards
What are the 4 barrier functions of membranes?
> prevent metabolite loss
protect against unwanted outside molecules
capacitor - stores electrical chemical energy
- creates electrochemical gradient
important for energy production + electrical signalling
What do plasma membranes need to be able to allow cells to do?
Receive info
Import + export info
What are the functions of membrane proteins?
>selective permeability > maintain ionic composition > maintain cytoplasmic pH > control cytoplasmic osmotic pressure > sense enviro > anchor cytoskelton > mediate cell-cell + cell-ECM interactions > carry out membrane requiring enzymatic reactions
What pH are most cells at?
7.2
What are the specialised water channels in plasma membranes called?
aquaporins
What % of hepatocytes does the plasma membrane make up?
2%
What type of molecules are lipids?
Amphipathic
- have hydrophobic + hydrophilic regions
How large are most membranes?
How many can fit into 1mm?
5nm
200,000
It is energetically favourable for lipids to form what?
Why is this?
Sealed compartments
No hydrophobic edges in contact w/ water
Describe the structure of glycerophospholipds
3 C glycerol
- 2 C ester linked to fatty acids
- 1 C linked to P
What can vary on lipids?
What do these variations give?
The head group
Different properties to the lipid e.g. charge
What are the other types of lipids found in membranes? Give examples.
Glycoplipids - sphingolipids
Sterols - cholesterol
Phospholipids -Glycerophospholipids + sphingolipids
Why isn’t it energetically favourable for a polar head to flip to the other leaflet?
Requires a polar molecule to move through a hydrophobic environment
Why is membrane fluidity important?
NOT energetically favourable for poor head to flip between leaflets
Allows for interactions to occur
- receptors need to move for dimerisation + signalling
What are the 4 factors that affect membrane fluidity?
> Temp
Saturation of acyl chains
Length of acyl chains
Cholesterol
