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Cell and Molec > Membrane Structure > Flashcards

Membrane Structure Flashcards

1
Q

Where are hydrophobic tails in the cell membrane?

A

The middle

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2
Q

Where are polar head groups in the cell membrane?

A

The outside

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3
Q

How much of the membrane is proteins?

A

~50%

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4
Q

What is an amphiphilic molecule?

A

Has both hydrophobic and hydrophilic properties

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5
Q

What are polar head groups made of?

A

Choline, phosphate, glycerol at the top

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6
Q

What are hydrophobic tails of the lipid bilayer made of?

A

Fatty acids (unsaturated, saturated)

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7
Q

Difference between unsaturated and saturated?

A 
Saturated = no double bonds
Unsaturated = double bonds

Unsaturated less likely to freeze

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8
Q

How many common phospholipids are there?

A

Four

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9
Q

What’s different between the phospholipids?

A

Charge, tail length, what’s on the head

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10
Q

How many sections are there of the polar head and which is most charged?

A

3, they could all be charged

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11
Q

What is the purpose of cholesterol?

A

Stops hydrocarbon chains from freezing, makes membrane less permeable

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12
Q

How does cholesterol attach to lipids?

A

Polar head group of cholesterol lines up with lipids

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13
Q

What happens if there’s too much cholesterol?

A

Things can’t get in and out of the cell

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14
Q

Why can the membrane act as a fluid?

A

Lipids can rotate, diffuse, or flex (twist)

But they barely ever flip-flop

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15
Q

Is there the same amount of lipid in each cell membrane?

A

No, composition varies a ton depending on the membrane

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16
Q

How much cholesterol do bacteria have?

A

None

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17
Q

If you do in situ hybridization on a membrane, will the components be distributed randomly?

A

No, components of lipids are organized

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18
Q

What is a lipid raft?

A

Microdomain in membrane that concentrates membrane proteins

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19
Q

What are glycolipids useful for?

A

Attaching cells together

Can be charged (alter electrical field)

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20
Q

You fuse a mouse and human membrane together with mouse in one area. What happens?

A

Membrane proteins diffuse, and all the membrane proteins are intermixed

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21
Q

How do you measure protein diffusion?

A

FRAP

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22
Q

What does FRAP stand for?

A

Fluorescent recovery after photobleaching

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23
Q

How does FRAP work?

A

Destroy (bleach) area with laser > measure how long it takes to recover

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24
Q

How can membrane proteins interact with the membrane?

A

Interact with protein embedded in membrane

Go through membrane

Get stuck in membrane

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25
Q

What are integral membrane proteins?

A

They go through membrane

26
Q

What are lipid-anchored proteins?

A

They bind to lipid molecules

27
Q

What are lipid-anchored proteins?

A

They bind to lipid molecules

28
Q

What do you need to see on a hydropathy plot to determine if a protein is an integral membrane protein?

A

Hydrophilic properties - many transmembrane domains

29
Q

Is + or - on a hydropathy plot hydrophilic?

A

+ (Going up)

30
Q

What’s in an aquaporin?

A

2 alpha helices go halfway through lipid bilayer

31
Q

What common domain does an integral membrane protein have?

A

Alpha helix, has hydrophilic amino acids which go through hydrophobic core

32
Q

What does ‘multipass’ in multipass transmembrane protein mean?

A

The protein passes through the membrane multiple times

33
Q

What happens as a multipass transmembrane protein fold?

A

Lipid molecules get displaced as protein folds in closer to itself

34
Q

What are porins?

A

Structures beta barrels create that let things through membrane

35
Q

What does a beta barrel look like?

A

A bunch of beta sheets overlapping

36
Q

What is the periplasm?

A

Space in between inner and outer membrane

37
Q

Where are carbohydrates?

A

Coat the extracellular side of the cell membrane

38
Q

What’s the function of the carbohydrate layer?

A

Protect it from mechanical forces, chemicals, etc

Cell recognition

39
Q

What’s the function of the carbohydrate layer?

A

Protect it from mechanical forces, chemicals, etc

Cell recognition

40
Q

What are detergents?

A

Small amphiphilic molecules

41
Q

What are micelles?

A

Heteromeric vesicle-like structures that detergents form

42
Q

Why use detergents to study membrane proteins?

A

Detergents grab proteins, mess with the lipid bilayer, and bring the proteins into solution

43
Q

How would you study a Na+/K+ pump?

A

Solubilize membrane proteins with detergent

Remove detergent

Make your own membrane outside of the cell

44
Q

What properties does a detergent need to be to grab a transmembrane protein without hurting it?

A

Nonionic, mild

45
Q

How were ATP synthases first studied?

A

Using mild detergents to bring them out of membrane

46
Q

How many domains do sperm cells have? why relevant?

A
  1. Shows there are distinct domains with distinct proteins
47
Q

What (generally) laterally immobilizes membrane proteins?

A

Protein-protein interactions (e.g. stick them there)

interactions with other cells,

48
Q

What types of molecules get across the membrane easily?

A

e.g. CO2, O2, N2 (hydrophobic molecules)

49
Q

How easily can water get across?

A

Kinda

50
Q

Can glucose/sucrose get across easily?

A

No, but a few do

51
Q

Can ions get through a cell membrane?

A

absolutely not

52
Q

What generally guides how easily a molecule crosses a membrane?

A

hydrophilicity

53
Q

How do membrane-impermeable molecules get across a membrane?

A

Solute transporter proteins

54
Q

What is the difference between transporter vs channel proteins?

A

Transporter = impermeable molecules bind, then they change conformation

Channel = they’re just tunnels for impermable molecules

55
Q

What sources of energy can drive active transport?

A

ATP, light, coupled molecules

56
Q

What’s a coupled transporter?

A

e.g. 3na+ with 2 K+

57
Q

What’s a uniporter?

A

One molecule goes through one direction

58
Q

What’s a symporter? (coupled transport)

A

A molecule and co-transported ion go through membrane the same way

59
Q

What’s an antiporter? (coupled transport)

A

Two molecules go through membrane the opposite way

60
Q

Take-home message for transport proteins?

A

They can be asymmetrically distributed in the membrane to cause specific planned movement

Cell and Molec (21 decks)

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