1. The Membrane Bilayer Flashcards Preview

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Flashcards in 1. The Membrane Bilayer Deck (16)

What is the dry weight composition of membranes?

40% lipid, 60% protein and 1-10% carbohydrate.
20% of total weight is water.


Why are membrane lipids thought of as Amphipathic molecules?

They contain both a hydrophilic and a hydrophobic moiety (region).


What is the structure of phospholipids?

Glycerol backbone with two fatty acids and one phosphate-head group attached.


How are phospholipids named?

According to their head group.


How do phospholipids vary?

There are a range of possible polar head groups. Also the fatty acid chains differ, between 14 and 24 carbons long, some have cigs double bonds that cause a kink.


What is sphingomyelin?

Like phosphotidylcholine (a phospholipid) but it's not based on a glycerol backbone.


What are cerebrosides?

Glycolipids with one sugar attached.


What are gangliosides?

Glycolipids with the head group as an oligosaccharide.


What is a lipid micelle?

A sphere of lipids with the hydrophilic head groups on the outside and hydrophobic tails facing inside.


What are liposomes?

The lipid bilayer being made into a sphere for drug delivery to specific tissues.


What are the movements allowed in the phospholipid bilayer?

Flexion, rotation, lateral diffusion and, rarely, flip flop.


How do cis double bonds affect the motion of phospholipids in the bilayer?

They cause kinking of the chain so there is more space between phospholipids and more room for movement.


Why are polyunsaturated fats important to a healthy diet?

They increase the space between phospholipids in the bilayer by causing kinks in the fatty acid tails so the membrane fluidity is increased.


What is the structure of cholesterol?

Polar head group, rigid planar steroid ring structure, non-polar hydrocarbon tail. It's really rigid.


How can cholesterol act as a buffer in the phospholipid bilayer?

Cholesterol reduces phospholipid packaging, hence increasing fluidity. But also reduces phospholipid chain motion, reducing fluidity. So it can alter fluidity in both directions.


What are the function of biological membranes?

Continuous, highly selective permeability barrier.
Control of the enclosed chemical environment.
Recognition or signalling molecules, adhesion proteins and immune surveillance.
Signal generation in response to stimuli.