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PSA712 Biochemistry > Membranes > Flashcards

Membranes Flashcards

1
Q

State 3 structures cellular membranes can be found in.

A
  1. Mitochondria
  2. ER
  3. Nucleus
  4. Golgi
  5. Vesicles
  6. Lysosome
  7. Plasma membrane
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2
Q

What model can be used to describe the movement of a cellular membrane?

A

Fluid mosaic model.

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3
Q

The phospholipid bilayers are held together by non-covalent bonds. It forms an impermeable barrier to what molecules?

A

Water-soluble (polar) molecules.

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4
Q

Fatty acids are long hydrocarbon chains with what functional groups found on either side?

A

Carboxyl end (COOH)

Methyl end (CH3)

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5
Q

The combination of a fatty acids and a glycerol molecule, via an ester bond, forms what molecule?

A

Triacylglycerol

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6
Q

Fatty acids have double bonds in their hydrocarbon chain, making them what?

A

Unsaturated fatty acids.

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7
Q

2 fatty acids and a phosphate molecule covalently bonded to a glycerol molecule form what molecule?

A

Phospholipid.

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8
Q

The phosphate molecule in a phospholipid bilayer is bonded to one of three molecules. What are these?

A

Choline
Ethanol amine
Serine

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9
Q

Sphingomyelin is a type of phospholipid found in what structures?

A

Myelinated neurones.

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10
Q

A cis double bond in a fatty acid chain forms what shape?

A

A kink.

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11
Q

A molecule having both hydrophobic and hydrophilic parts is described as what?

A

Amphipathic.

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12
Q

State whether the polar head and non-polar tails of a phospholipid bilayer are hydrophobic or hydrophilic.

A
  1. Polar head - hydrophilic

2. Non-polar tail - hydrophobic.

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13
Q

Define polarity including the use of electrons.

A

Polarity refers how equally two atoms share electrons.

Non-polar molecules share electrons equally.

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14
Q

Polar molecule dissolve easily. What does this have to do with entropy?

A

Polar molecules will dissolve meaning they are more energetically favourable and so entropy increases.

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15
Q

Non-polar molecule do not dissolve. What does this have to do with entropy?

A

Non-polar molecules do not dissolve and so are not energetically favourable, entropy decreases.

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16
Q

The amphipathic nature of phospholipid causes what to form?

A

Bilayers and micelles.

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17
Q

The edges of the bilayer in a micelle form what structure?

A

A continuous spheroid.

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18
Q

If membranes become damaged, how will they heal to ensure water doesn’t encounter the hydrophobic tails?

A

Formation of a continuous spheroid.

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19
Q

Membrane fluidity refers to the what of the membrane?

A

Viscosity.

20
Q

What 3 ways can bilayers move?

A
  1. Flex
  2. Rotate
    3 Move laterally across the outer leaflet

CANNOT FLIP FLOP BETWEEN OUTER AND INNER LEAFLETS

21
Q

At low temperatures, the bilayer can undergo a phase transition and become rigid as the phospholipids pack together. What two things help to prevent this?

A
  1. Cis double bonds.

2. Cholesterol

22
Q

How do cis double bonds prevent phospholipids from packing closely together?

A

Makes the membrane thinner.

Creates a characteristic ‘kink’, preventing phospholipids from packing together.

23
Q

How does cholesterol prevent the phospholipid from packing closely together?

A

The orientation of cholesterol means that the steroid ring region of the cholesterol stiffens the upper region of the fatty acid chain.

24
Q

The stiffening of the upper region of the fatty acid chain does what to the phospholipid?

A
  1. Prevents the phospholipid from packing together.
  2. Less able to move laterally.
  3. Less fluid.
25
Q

What are lipid rafts?

A

Cholesterol-rich plasma membrane domains.

26
Q

Sphingolipids have long and saturated fatty acid chain and the attractive forces are strong enough to do what?

A

Hold adjacent molecules together in lipid rafts.

27
Q

Glycoproteins and glycolipids are found on membranes, acting as protective mechanisms. This is known as what?

A

Glycocalyx

28
Q

List four types of proteins found in cellular membranes.

A
  1. Integral/transmembrane proteins
  2. Peripheral membrane proteins
  3. Single pass proteins
  4. Multi pass proteins
  5. Alpha helix proteins
  6. Beta-sheet barrel
  7. Embedded in the membrane
  8. Covalently bonded to lipids
  9. Non-covalently attached to integral membrane proteins
29
Q

In what two ways can proteins be bonded to the cellular membrane?

A
  1. Covalently

2. Non-covalently

30
Q

The lipid bilayer is an impermeable barrier to polar molecules. State 2 things that this contributes to for the cell.

A
  1. Enables a cell to maintain a different environment to the outside.
  2. Transport molecules across membranes (requires specialised proteins).
31
Q

What does the term glycosylated mean?

A

Carbohydrate is attached to a hydroxyl or another functional group.

32
Q

All transport proteins are transmembrane, multi-pass proteins. What does this mean?

A

There is not contact with the hydrophobic core - solutes can pass without meeting hydrophobic fatty acid tails.

33
Q

State two types of membrane transport proteins?

A
  1. Carrier

2. Channel

34
Q

How do carrier proteins transport solutes across the membrane?

A

Solute binds to carrier proteins and undergoes a conformational change which allows solute to enter the cell.

35
Q

How do channel proteins transport solutes across phospholipid bilayers?

A

Interact weakly with solutes, forms aqueous pore that solutes pass through.

36
Q

Which types of membrane transport proteins are more selective, channel or carriers?

A

Channel proteins.

37
Q

Active transport is the process used to describe the pumping of solutes across a membrane, against their concentration gradient. What membrane transport protein facilitates this?

A

Carrier proteins.

38
Q

Eukaryotes carry out active transport via what two mechanisms?

A
  1. Coupled carriers

2. ATP driven pumps

39
Q

State 2 types of coupled carriers.

A
  1. Symporters

2. Antiporters

40
Q

How do coupled carriers function?

A

Energy from the electrochemical gradient could be used to transport another ion against its concentration.

41
Q

State the function of antiporters.

A

Antiporters transport ions along their concentration gradients, releasing free energy to transport another molecule against its concentration gradient.

OPPOSITE DIRECTIONS

42
Q

TRUE OR FALSE:

Coupled carriers participate in secondary active transport.

A

TRUE

43
Q

What is the function of symporters?

A

Transport ions down their concentration gradient alongside wanted molecules, against their concentration (same transmembrane protein).

SAME DIRECTION

44
Q

Give an example of an antiporter.

A

Malate aspartate shuttle.

45
Q

ATP driven pumps are termed as primary transport. Describe how the sodium-potassium pump functions?

A
  1. Sodium ions enter ATPase pump
  2. Release of energy from ATP hydrolysis forms a conformational change. Pi remains bound to carrier protein.
  3. Allow sodium to move out of the cell.
  4. Potassium binds to binding site on ATPase pump and ions move into the pump.
  5. Phosphate group leaves the ATPase pump.
  6. This changed the carrier protein shape and reverts back to its original shape.
  7. Potassium released into cell.
46
Q

The V-ATPase pump in a lysosome helps to maintain the acidity how?

A

Maintained through pumping H+ ions across the membrane via the V-ATPase pump.

47
Q

Channels are narrow and highly selective pores - more commonly referred to as what?

A

Gated channels.

PSA712 Biochemistry (11 decks)

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