1.1 The Membrane Bilayer Flashcards
Describe the general composition of the dry weight of the membrane bilayer
40% lipid
60% protein
1-10% carbohydrate
List the functions of the membrane bilayer (5)
Continuous, highly selective permeability barrier Control of the enclosed environment Communication Recognition Signal generation
What % of the total membrane weight is water?
20%
What are phospholipids made up of?
Fatty acids
Glycerol
Phosphate
Head group
Define ‘amphipathic’
Both hydrophilic and hydrophobic
Give examples of species that can act as head groups in a phospholipid (4)
Choline
Amines
Amino acids
Sugars
What length of carbon chain is most prevalent in a phospholipid?
16-18
How does sphingomyelin differ from a normal phospholipid?
Sphingomyelin does not use glycerol
Describe a glycolipid
No phosphate joining group
Sugar containing lipids
Define a ‘cerebroside’
A phospholipid with a sugar monomer as the head group
Define a ‘ganglioside’
A phospholipid with an oligosaccharide as the head group
Describe a lipid micelle
A ring of phospholipids with the hydrophilic heads facing outwards and the hydrophobic heads facing inwards
Describe a lipid bilayer structure
2 layers of phospholipids. The hydrophobic tails face each other and the hydrophilic heads face outwards
Describe the movement of ‘flexion’
Side to side movement
Describe the movement of ‘rotation’
Stationary movement in a circle
Describe the movement of ‘lateral diffusion’
Phospholipids move along the chain laterally
Describe the movement of ‘flip-flop’
Moves from the inner layer to the outer layer
Explain the function of a cis double bond in a phospholipid carbon chain. Where do the unsaturated chains come from?
Double bonds cause the chains to kink. This results in the chains being more spaced out which reduces phospholipid packing. The unsaturated chains are required from the diet.
Describe the structure of cholesterol
Cholesterol has a rigid planar steroid ring structure with a polar head group. It also has a more flexible non-polar hydrocarbon chain.
How does cholesterol affect the fluidity of the bilayer
Reduces: rigid structure causes reduced chain motion
Increases: reduces phospholipid packing