Session 1 - Lipids, Proteins + Membrane Structure Flashcards

1
Q

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

A
  • 40% Lipid
  • 60% protein
  • 1-10% Carbohydrate
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2
Q

Describe the structure of a phospholipid molecule

A

Head group - range of polar molecules (aa’s, choline so, amines and sugars)
Fatty acid “tail” - Lots of variety (C16+18 most common), unsaturated, cis double bond creates a kink in chain

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3
Q

What are Glycolipids?

A

Sugar containing lipids

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4
Q

What is Sphingomyelin?

A

Only phospholipid not based on glycerol (when in membrane is very similar to others)

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5
Q

What are Cerebrosides?

A

Glycolipid with sugar monomers as head groups

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6
Q

What are Plasmalogens?

A

Non-classical Phospholipids

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7
Q

What are Gangliosides?

A

Glycolipids with sugar oligosaccharides for head groups

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8
Q

What does the distribution of lipids in the mebrane depend on?

A

Tissue type and function

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9
Q

What two structures do Amphipathic molecules readily form in water?

A

Micelles and Bilayers

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10
Q

What forces and between what regions drive Bilayer formation?

A

Vdws between the hydrophobic fatty acid chains

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11
Q

Name the four ways that lipids can move in a membrane?

A
  • intra-chain motion
  • Axial rotation
  • Lateral diffusion along same plane
  • Flip-Flop
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12
Q

Name the ways membrane proteins can move?

A
  • Lateral movement
  • Rotation
  • Conformational change
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13
Q

What restricts membrane protein movements?

A
  • Cholesterol levels in particular region
  • Associations with other membrane proteins
  • Association with extra-membranous proteins (e.g cytoskeleton)
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14
Q

How do Peripheral proteins bind to the membrane and how can they be removed?

A
  • Electrostatic forces and H-bonds

- pH changes or Ionic strength changes

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15
Q

How are integral membrane proteins bound to the membrane and how can they be removed?

A
  • Interact with hydrophobic region of bilayer

- Agents that compete for hydrophobic interactions (e.g detergents, organic solvents)

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16
Q

How is membrane protein synthesis different to secretory protein synthesis?

A

The protein has to span the membrane not sit solely within it

17
Q

How does a membrane protein achieve its spanning of the membrane in its synthesis?

A

Through the addition of a stop transfer signal which is a highly hydrophobic chain of around 20 aa’s

18
Q

What are Hydropathy plots used for?

A

To see how many transmembrane regions a protein has

19
Q

Why is membrane asymmetry important?

A

Important for biological function

I.e Ensure receptors are situated on the same side of the membrane that their substrate will be

20
Q

Why is the “kink” in the FA chain important?

A

It decreases phospholipid packing and hence increases fluidity of the membrane

21
Q

How does cholesterol increase packing in the membrane?

A

Forms H-bonds with FA chain

22
Q

How does cholesterol decrease membrane fluidity?

A

Decreases the packing by being a physical barrier between chains

23
Q

What is protein lateral diffusion affected by?

A
  • Size
  • Aggregation
  • Association with other proteins (intra or extracellular)
  • Amount of cholesterol in near vicinity
24
Q

What is the erythrocyte cytoskeleton composed of and why is it important?

A

Spectrin and Actin

Maintains shape of RBCs

25
Q

How does the cytoskeleton attach to the membrane?

A

Ankyrin and Glycophorin
Bound to
Band 3 and Band 4.1 respectively

26
Q

What are Haemolytic anaemias in general?

A

RBCs become spherical and are therefore subject to increased lysis due to shearing forces of capillary beds

27
Q

What is Hereditary Spherocytosis?

A

Spectrin levels depleted, RBCs round up, leads to increased lysis
Bone marrow cannot compensate and hence a haemolytic anaemia results

28
Q

What are Amphipathic molecules?

A

Molecules with both Hydrophobic and Hydrophilic moieties

29
Q

What is Hereditary Elliptocyosis?

A

Spectrin molecules are unable to form heterotetramers, RBCs form elliploid shape (rugby ball) and a Haemolytic anaemia results