1.1 The Membrane Bilayer Flashcards Preview

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Flashcards in 1.1 The Membrane Bilayer Deck (15)
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0
Q

What is the composition of the dry weight of the membrane?

A

40% lipid
60% protein
1-10% carbohydrate

1
Q

What are the five main functions of membranes?

A
  • continuous, highly selective permeability barrier
  • control of the enclosed chemical environments
  • communication
  • recognition
  • signal generation in response to stimuli
2
Q

What are amphipathic molecules?

A

Have hydrophilic and hydrophobic regions

3
Q

What is the structure of a phospholipid?

A

Glycerol backbone
Very long fatty acid chains
Small head group

4
Q

What are the four different head groups?

A

Choline
Amines
Amino acids
Sugars

5
Q

The fatty acid chains are roughly the same length. What is the advantage of this?

A

The bilayer will be roughly the same thickness all the way along

6
Q

What are the features of sphingomyelin?

A

Not based on glycerol but resembles other phospholipids

Has a phosphate group and a fatty acid chain

7
Q

What are the two classes of glycolipids?

A

Cerebroside - glycolipid with single carbohydrate

Ganglioside - glycolipid with complex carbohydrates

8
Q

Describe bilayer formation

A

When phospholipids are put in water the Van Der Waals attraction between the hydrophobic tails drives formation of a bilayer

9
Q

What forces maintain the bilayer structure?

A

Hydrogen bonds between hydrophilic moieties
Interactions between the hydrophilic groups and water
Electrostatic attractions

10
Q

What are the four different motions of phospholipids?

A

Flexion = vibration
Rotation
Lateral diffusion
Flip-flop

11
Q

How do the cis double bonds between fatty acid molecules create fluidity?

A

Reduce phospholipid packing by separating the phospholipid molecules

12
Q

What are the modes of motion of proteins in the bilayer?

A

Conformational change
Rotational
Lateral

13
Q

What restricts the mobility of the membrane?

A

Lipid mediated effects
Membrane protein associations
Extra-membranous protein association - e.g. Cytoskeleton

14
Q

What is the importance of cholesterol in the plasma membrane?

A

Stabilises the plasma membrane as it’s presence means less energy is needed to melt the crystalline phospholipid into fluid membrane
Binding reduces motion of the membrane but increases space between phospholipid molecules so overall increases fluidity