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BCMB2002 > Membranes (wk 5 and 6) > Flashcards

Membranes (wk 5 and 6) Flashcards

1
Q

T/F:

Different compartments of the cells all have the same environments of the cytosol

A

False

They can have different environments than the cytosol

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2
Q

List some organelles that may have two membranes rather than one

A

Nucleus
Mitochondria
Chloroplast

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3
Q

In organelles that have two membranes, the inter-membrane is topologically equivalent to the ______ of the cell

A

Exterior

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4
Q

In organelles that have two membranes, the internal aqueous space is topologically equivalent to the _____ of the cell

A

Cytoplasm

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5
Q

List some functions of lipids

A 
Store energy
Insulation from the environment
Water repellent
Membrane structure
Cofactors for enzymes
Signalling molecules
Pigments
Antioxidants
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6
Q

What is the most important function of membranes?

A

Allows cells to exist and be unique

Allows differentiation of different cell types/organs

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7
Q

T/F:

Unsaturated fatty acids pack in a fairly orderly way because of favourable reactions

A

False

Saturated fatty acids

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8
Q

T/F:
Unsaturated cis fatty acids have a lower melting point resulting in less thermal energy to disrupt disordered packing of unsaturated fatty acids

A

True

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9
Q

Why do unsaturated fatty acids pack badly?

A

Double bonds cause kinks

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10
Q

What’s the benefit of having more saturated fats compared to unsaturated fats in the blood stream?

A

More thermostable, can survive heat better

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11
Q

How do trans fatty acids form?

A

Partial dehydrogenation of unsaturated fatty acids

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12
Q

T/F:

Trans fatty acids pack more regularly and show higher melting points than cis forms

A

True

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13
Q

T/F:

Consuming trans fatty acids decreases risk of cardiovascular disease

A

False

Increases

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14
Q

T/F:

The properties of the tail group in a lipid determines the surface properties of membranes

A

False

properties of the head groups will determine the surface properties of the membranes

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15
Q

Describe the net charge of the inner and outer side of the membrane and what this allows

A

The charges will be different
Allows polarization and depolarization
Allows for synapses
Life without this would not exist

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16
Q

Which lipid is the major constituent of eukaryotic cell membranes?

A

Phosphatidylcholine

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17
Q

T/F:

Bacterial cells can synthesise phosphatidylcholine

A

False

Therefore our immune system can recognise bacterial cells and remove them

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18
Q

T/F:

The backbone of sphingolipid is glycerol

A

False

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19
Q

T/F:

The backbone of sphingolipids is a long-chain amino alcohol sphingosine

A

True

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20
Q

Which phospholipid constitutes myelin that surrounds nerves?

A

Sphingomyelin

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21
Q

What confers flexibility to phosphatidylcholine rather than sphingomyelin?

A

Phosphatidylcholine has two saturated bones (double bonds)

22
Q

What is the physiological role of sterols in the cell?

A

Modulate fluidity and permeability
Thicken the plasma membrane
Most bacteria lack sterols

23
Q

How can you obtain cholesterol?

A

In food

Synthesize in the liver

24
Q

When do micelles form?

A

When in the presence of a solution of amphipatic molecules that have larger heads than tails

25
Q

T/F:

A vesicle has a single layer

A

False

Double layer

26
Q

How does sterol affect membranes?

A

Planar so makes the membranes rigid

27
Q

What type of components can the central aqueous cavity of a vesicle contain?

A

Dissolved molecules

28
Q

What shape are the individual units of the lipid monolayer

A

Cylindrical

29
Q

List some of the roles of membranes

A

• Define the boundaries of the cell
• Allow import and export
o Selective import of nutrients (e.g., lactose)
o Selective export of waste and toxins (e.g., antibiotics)
• Retain metabolites and ions within the cell
• Sense external signals and transmit information into the cell
• Provide compartmentalization within the cell
o separate energy-producing reactions from energy-consuming ones
o keep proteolytic enzymes away from important cellular proteins
• Produce and transmit nerve signals
• Store energy as a proton gradient
• Support synthesis of ATP

30
Q

What type of forces stabilise membranes?

A

Non-covalent forces

Especially the hydrophobic effect

31
Q

T/F:

Lipid bi layers in cells are symmetric

A

False

asymmetric

32
Q

T/F:

Carbohydrates are always intracellular to the membrane

A

False

always extracellular

33
Q

Are integrins firmly or weakly attached to the membrane?

A

Firmly attached

34
Q

Are proteins firmly or weakly attached to the membrane?

A

Weakly attached

Can be removed easily

35
Q

T/F:

Fatty acids can diffuse laterally in membranes

A

True

36
Q

T/F:

Glycolipids are mostly found on the inside of membranes

A

False
mostly on the outside
they are used as secondary markers for our immune response

37
Q

T/F:

Prokaryotes lack sterols

A

True

38
Q

T/F:

Plasma membranes have lots of cholesterol that confer flexibility

A

False

lots of cholesterol that confer rigidity

39
Q

Which side of the bilayer is more positively charged?

A

Outside leaflet

40
Q

T/F:

Membranes are permeable to polar molecules

A

False

non-polar

41
Q

Which part of the membrane does CO2 interact with when it passes easily through

A

Interacts with the fatty part

42
Q

What two phases can the membrane be in?

A

Gel phase= molecules do not move around

Fluid phase= molecules can move around

43
Q

Which phase are membranes most likely to be found in physiological conditions?

A

Fluid phase

44
Q

What mostly determines membrane fluidity?

A

Fatty acid composition

45
Q

What types of fatty acids are required for a membrane to maintain their fluidity?

A

Unsaturated fats
These have lower melting points
Need them to maintain the fluidity

46
Q

T/F:

Proteins move faster than lipids

A

False

47
Q

T/F:

Lateral diffusion of individual lipids is fast

A

True

48
Q

T/F:

‘flip flop’ rarely occurs

A

True

49
Q

Why are spontaneous flips from one leaflet to another rare (transverse diffusion)

A

The charged polar head must traverse the hydrophobic tail region of the membrane

50
Q

Floppases move individual lipids from the ___ to the ____

A

inside to outside

51
Q

Flippases move individual lipids from the outside to the inside

A

outside to the inside

52
Q

Scramblases move lipids in ____

A

either direction, towards equilibrium

BCMB2002 (9 decks)

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