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Cell Biology Topic C > Membrane Structure & Function > Flashcards

Membrane Structure & Function Flashcards

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1
Q

How thin are membranes?

A

8nm.

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2
Q

What are membranes made of?

A

Lipids, proteins and sometimes carbohydrates.

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3
Q

What do plasma membranes do?

A

Separate cells from the environment and allow them to respond to the environment.

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4
Q

What do internal membranes do?

A

Segregate functional compartments within cells and create organelles.

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5
Q

What to membranes allow for?

A

Controlled transport of materials across permeability barriers.

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6
Q

What are the most abundant membrane lipids?

A

Phospholipids.

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7
Q

What are the two characteristics of phospholipids?

A

They have both hydrophilic and hydrophobic regions.

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8
Q

What does amphipathic mean?

A

Its both hydrophobic and hydrophilic.

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9
Q

What do phospholipids for together?

A

A fluid mosaic lipid bilayer.

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10
Q

How often do phospholipids form membranes?

A

Spontaneously.

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11
Q

What do the amphipathic properties of phospholipids lead to?

A

The spontaneous formation of bilayers.

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12
Q

Hydrophobic tails contact…

A

Each other.

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13
Q

Hydrophilic heads point in…

A

Opposite directions.

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14
Q

What do the phospholipids contact on each side of the membrane?

A

Aqueous Solutions.

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15
Q

Are the components of the fluid mosaic model static?

A

No, everything moves about and is capable of lateral diffusion.

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16
Q

Where can proteins be found within the mosaic?

A

Spanning the whole membrane or just on either of the sides.

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17
Q

What is freeze-thaw?

A

An EM technique that rapidly freezes cells and then they are slip along the middle.

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18
Q

Lateral movement of phospholipids is…

A

Very frequent.

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19
Q

Flip-flop movement of phospholipids is…

A

Exceedingly rare.

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20
Q

When do phospholipids flip-flop?

A

When carried by a protein.

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21
Q

What influences phospholipid movement?

A

The composition of bilayers.

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22
Q

What prevents tight molecular packing?

A

High levels of fatty acid tails.

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23
Q

What increases phospholipid movement and membrane fluidity?

A

The lack of tight molecular packing due to the high level of fatty acid tails.

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24
Q

What will make a membrane more solid?

A

Cholesterol at physiological temperatures.

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25
Q

Where are phospholipids made?

A

Smooth ER.

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26
Q

What are the name of the proteins that flip-flop phospholipids?

A

Flippases.

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27
Q

What targets ribosomes to ER membrane?

A

The signal sequences of membrane proteins.

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28
Q

What is the protein pore that ribosomes dock on during membrane synthesis called?

A

Translocon.

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29
Q

During membrane synthesis, what happens after the ribosome has docked?

A

Protein synthesis continues and the protein is extruded into the ER lumen or a membrane.

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30
Q

What determines the specific functions of phospholipids?

A

Proteins.

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31
Q

Which proteins span the membrane?

A

Integral membrane proteins.

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32
Q

Which proteins can form pores?

A

Ones with amphipathic alpha-helices.

33
Q

What can protein functions be categorised into?

A

Transport, enzymatic activity, signal transduction, cell-cell/cell-solute recognition, intercellular connections and attachments to the cytoskeleton or ECM.

34
Q

In channels, materials can only pass which way with out energy?

A

Down the concentration gradient.

35
Q

To move a solute up a concentration gradient requires?

A

Energy in the for of ATP.

36
Q

What does a pore allow for?

A

Movement of material from one side to the other.

37
Q

Related enzymes can often be associated?

A

Together.

38
Q

In some cases, enzymes can be linked to proteins that…

A

Are involved in signal transduction.

39
Q

Binding of molecules activates what?

A

Signal transduction pathways.

40
Q

What happens when a signalling molecule binds to a receptor?

A

It changes its shape.

41
Q

What doe glycosylated molecules act as?

A

Cellular identity tags.

42
Q

Some viruses can entre cells by binding to?

A

Surface glycoproteins.

43
Q

How do viruses initially infect cells?

A

By binding to the plasma membrane.

44
Q

HIV invade CD4+T cells by?

A

Binding to CD4 and CCR5 proteins.

45
Q

What can prevent HIV and how to anti-HIV drugs use this?

A

A lack of CCR5 proteins prevents infection and anti-HIV drugs try to block these proteins.

46
Q

How do tight junctions work?

A

They prevent the movement of substances through gaps between the cells.

47
Q

Which type of junctions bind cells together?

A

Desmosomes.

48
Q

What do gap junctions permit?

A

Intercellular cytoplasmic continuity.

49
Q

What interaction is important in giving cells shape?

A

Interactions of cytoskeleton with membrane proteins.

50
Q

What do integrins do?

A

Integrate extracellular and intracellular environments.

51
Q

The orientation of proteins is determined by?

A

Amino acid sequences.

52
Q

Biological membranes are important barriers between what?

A

Different environments.

53
Q

Part of the membrane’s barrier function is to do with what?

A

The hydrophobic nature of the inner membrane.

54
Q

How can hydrophilic substances such as sugars or ions cross the membrane?

A

They need to be carried by something.

55
Q

What is passive transport?

A

Movement of solutes across a membrane with no energy input.

56
Q

How is passive transport driven?

A

Using concentration gradients.

57
Q

What is active transport?

A

Transport that moves solutes against their concentration gradients with energy from ATP.

58
Q

What is diffusion?

A

Passive transport aided by specific proteins to move solutes down their concentration gradients.

59
Q

If a membrane does not allow the movement of a solute, the solute can still?

A

Influence solution behaviour.

60
Q

Tonicity is defined as what?

A

As the ability of a solution to make a cell gain or lose water.

61
Q

What is a channel?

A

A protein that passes through the membrane which has a hole in it to allow the passage of materials.

62
Q

How to gated channels open and close?

A

In response to changes in membrane potential.

63
Q

How to gated channels open and close in the nervous system?

A

In response to neurotransmitters.

64
Q

Many molecules are transported across membrane by what?

A

Carriers.

65
Q

When the solute binds on one side of the channel, what is created?

A

A conformational change.

66
Q

What does the conformational change allow the solute to do?

A

Be taken across the membrane and released.

67
Q

All proteins in active transports are?

A

Carriers and not channels.

68
Q

In animal cells, sodium is…

A

High outside and low inside.

69
Q

In animal cells, potassium is…

A

Low inside and high outside.

70
Q

In cystic fibrosis thick mucus clogs up in certain areas due to what?

A

A defective Cl pump.

71
Q

What makes up an electrochemical gradient?

A

The combination of concentration and electrical gradients.

72
Q

What are the main generators of membrane potentials in plants, fungi and bacteria?

A

Proton pumps.

73
Q

What is used to import sucrose in plants?

A

H+ pumps.

74
Q

What is transported packed into membrane vesicles?

A

Most large molecules such as proteins or polysaccharides,.

75
Q

What happens in exocytosis?

A

Material is realised from the cell.

76
Q

What happens in endocytosis?

A

Material is taken up into cells.

77
Q

How many types of endocytosis are there?

A

3.

78
Q

What is familial hypercholesterolemia?

A

A defect of receptor-mediated endocytosis.

Cell Biology Topic C (7 decks)

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