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Membranes & Receptors > 1. Lipids, Proteins and Membrane Structure > Flashcards

1. Lipids, Proteins and Membrane Structure Flashcards

0
Q

What proportion of the dry weight of a membrane do lipids make up?

A

40%

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1
Q

Why would different regions of a cell membrane have different proteins?

A

Different regions can have different functions e.g. Adherence, secretion/absorption, synapses, interaction with basement membrane etc.

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2
Q

What proportion of the dry weight of the membrane do proteins make up?

A

60%

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3
Q

What else makes up the dry weight of the membrane bilayer.

A

Carbohydrates

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4
Q

When hydrated, how much of the total weight does water make up and how is water associated with the membrane?

A

20%

Hydrogen bonded to the cell membrane surface

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5
Q

What four groups make up a phospholipid molecule?

A

Polar head group
Phosphate group
Glycerol
Fatty acid chains

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6
Q

What are the most predominant lengths of fatty acid chains?

A

C16

C18

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7
Q

What can produce a kink in the phospholipid?

A

Cis orientated double bond in a fatty acid tail

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8
Q

What four chemicals can act as polar heads?

A

Choline
Amines
Amino acids
Sugars

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9
Q

What makes a glycolipid different to a phospholipid?

A

Carbohydrate molecule instead of a phosphate head

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10
Q

What are the two types of glycolipid?

A

Cerebrosides

Gangliosides

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11
Q

What type of head group is present on a ganglioside glycolipid?

A

Oligosaccharide

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12
Q

What type of head group is present on a cerebroside lipid?

A

Sugar monomer

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13
Q

What are the forces that interact between hydrophobic tails in a membrane?

A

Van der Wall’s forces

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14
Q

What are the two types of lipid bilayers that can form?

A

Phospholipid bilayer

Lipid mycelle

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15
Q

What 4 types of motion can phospholipids undergo?

A

Flexion (vibration)
Rotation
Lateral diffusion
Flip flop

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16
Q

Which type of phospholipid motion requires the most energy and why?

A

Flip flop as it is the least thermodynamically favourable

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17
Q

What do the Cis bonds in the fatty acid tails of phospholipids result in?

A

Reduced phospholipid packing
More movement
More fluidity of membrane

18
Q

What does our diet need to include for phospholipids and where can we get this from?

A

Polyunsaturated fats
Vegetable oils
Tuna/Salmon
Seeds

19
Q

What property does the planar ring in cholesterol have?

A

Rigidity

20
Q

What percentage of lipids in a phospholipid bilayer are cholesterol?

A

45%

21
Q

How does cholesterol interact with the phospholipid bilayer?

A

Locks onto adjacent phospholipid via a hydrogen bond

22
Q

How does cholesterol reduce fluidity of the membrane at high temperatures?

A

Reduces the phospholipid’s fatty acid chain’s motion

23
Q

How does cholesterol increase fluidity of the membrane at low temperatures?

A

Reduced phospholipid packing

24
Q

What is cholesterol’s overall effect on the membrane?

A

Maintains a constant fluidity at a wide range of temperatures

25
Q

What are the 3 functional pieces of evidence for proteins existence in the membrane?

A

Facilitated diffusion
Ion gradients
Specificity of cell responses

26
Q

What are the 2 biochemical pieces of evidence for protein existence in the membrane?

A

Membrane fractionation

Freeze fracture

27
Q

What type of mobility can proteins NOT do in membrane bilayers and why?

A

Flip flop
Requires too much energy as they have large hydrophilic moieties which associate with the polar heads and water on the outsides of the membrane

28
Q

What are the 3 types of mobility proteins can do in bilayers?

A

Conformational change
Rotation
Lateral diffusion

29
Q

What restricts protein movement in bilayers?

A

Protein aggregation
Tethering (e.g. Cytoskeleton)
Interaction with other cells

30
Q

What are peripheral membrane proteins and how do they bond?

A

Proteins bound to the surface of a membrane
Hydrogen bonds
Electrostatic bonds
Disulphide bonds

31
Q

How can peripheral proteins be removed from the membrane?

A

pH change

Ionic strength

32
Q

What are integral proteins?

A

Proteins that interact extensively with hydrophobic domains of the lipid bilayer (can be transmembrane proteins)

33
Q

How can integral proteins be removed from the membrane?

A

Detergents

Organic solvents

34
Q

What type of secondary structure do transmembrane domains often have and how many residues does it take to cross the membrane?

A

Alpha helix

18 - 22 amino acid residues

35
Q

What is a hydropathy plot?

A

Checking individual residues to check how hydrophobic/hydrophilic their R groups are
18-22 hydrophobic residues indicates a membrane cross hence a hydropathy plot can be used to tell how many times a protein crosses the membrane

36
Q

What forms the cytoskeleton network on the erythrocyte membrane?

A

Actin

Alpha and beta spectrin molecules wound together to form a heterotetramer

37
Q

Which adapter proteins do band 3 and glycophorin A attach to respectively?

A

Ankyrin and band 4.1

38
Q

Which integral proteins do ankyrin and band 4.1 bind to respectively?

A

Band 3 and glycophorin A

39
Q

What is hereditary spherocytosis and what is it’s cause?

A

Erythrocytes become more spherical hence are less resistant to lysis and get cleared by the spleen
Cause by a 50% depletion in spectrin due to one allele not being expressed

40
Q

What is hereditary eliptocytosis and what is its cause?

A

Erythrocytes are fragile eliptoid shaped cells

Caused by defect in spectrin molecule stopping heterotetramers from forming

41
Q

What are the main signs/symptoms of haemolytic anaemias?

A

Low erythrocyte count hence low Hb

Fatigue

42
Q

What is the treatment for haemolytic anaemias?

A

Blood transfusions

43
Q

What is the sequence of hydrophobic amino acids called which cause that section of the synthesised protein to stay in the membrane?

A

Stop transfer signal

Membranes & Receptors (10 decks)

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