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Biology AS Rafa > 2.5 Biological Membranes > Flashcards

2.5 Biological Membranes Flashcards

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1
Q

What is the fluid mosaic model?

A

Theory of cell membrane structure with proteins embedded in a sea of phospholipids

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2
Q

What is a glycolipid?

A

A lipid /phospholipid with a chain of carbohydrate molecules attached.

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3
Q

What is a glycoprotein?

A

A protein with a chain of carbohydrate molecules attached.

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4
Q

What is the plasma membrane?

A

Cell surface membrane.

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5
Q

How can substances get into the cell?

A
  • small = diffuse
  • some substances dissolve in lipid layer and pass through
  • protein channels and carrier proteins.
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6
Q

What are the roles of the plasma membrane?

A
  • separates from external environment
  • regulates transport of materials
  • contain enzymes
  • has antigens so immune system recognises as self
  • chemical signals to other cells
  • receptors for chemical signals
  • site of chemical reactions
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7
Q

What are the inner membranes of mitochondria called?

A

Cristae

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8
Q

What are Cristae used for?

A

Large surface area for aerobic respiration and localise enzymes for respiration.

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9
Q

What are the inner membranes of chloroplasts called?

A

Thylakoid membranes.

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10
Q

What do thylakoid membranes do?

A

House chlorophyll and some photosynthesis.

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11
Q

What are there on the plasma membranes of epithelial cells that line the small intestine?

A

Digestive enzymes that catalyse the final stages of the breakdown of certain sugars.

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12
Q

What makes the fluid mosaic model fluid?

A

The lipid molecules can change places with each other.

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13
Q

How thick is the phospholipid bilayer?

A

7nm

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14
Q

What do carbohydrate molecules on the outside of the membrane do?

A

Attract water with dissolved solutes.

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15
Q

What is another name for the outside of the membrane?

A

Glycocalyx

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16
Q

What does cholesterol do?

A

Gives mechanical stability and flexibility and resist the effects of temperature changes.

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17
Q

What are channel and carrier proteins?

A

Integral proteins.

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18
Q

How is that glycocalyx formed?

A

From carbohydrate chains attached either to lipids or proteins on the membrane.

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19
Q

How are the membranes of neurones specialised?

A

Protein channels and carriers in the long axon allow ions to bring the conduction of electrical impulses.

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20
Q

How are the plasma membranes of white blood cells specialised?

A

Have special proteins receptors that enable them to recognise the antigens on foreign cells.

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21
Q

Define diffusion.

A

The net movement of molecules from and area of high concentration of that molecule to an area of low concentration.
May or may not be across a membrane
Is passive

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22
Q

Define facilitated diffusion.

A

The net movement of molecules from an area of high concentration of that molecule to an area of low concentration, across a partially permeable membrane via protein channels or carriers
Is passive

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23
Q

Why is water a special case for diffusion?

A

Molecules are polar and insoluble in the lipid in the phospholipid bilayer.

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24
Q

Why is water able to diffuse through cell membranes?

A

It is present in great concentrations.

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25
Q

What are specific water channel proteins called?

A

Aquaporins

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26
Q

How is the concentration gradient maintained?

A

The molecules that enter the cells are used for metabolic reactions.

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27
Q

What factors affect the rate of simple diffusion?

A
  • temperature
  • diffusion distance
  • surface area
  • size of diffusing molecule
  • concentration gradient
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28
Q

What molecules undergo facilitated diffusion?

A

Small molecules that have polarity are insoluble in lipid as they cannot interact with the hydrophobic tails of the lipid bilayer.

29
Q

Define osmosis.

A

Passage of molecules down their water potential gradient, across a partially permeable membrane.

30
Q

Define water potential.

A

Measure of the tendency of water molecules to diffuse from one region to another.

31
Q

What is the unit of water potential.

A

KPa

32
Q

What is the water potential of pure water?

A

0kPa

33
Q

What is it called when a cell swells and bursts due to too much water?

A

Cytolysis

34
Q

What is it called when animal cells shrivel?

A

Crenated

35
Q

What is it called when the cytoplasm of plant cells shrinks and the membrane pulls away from the cell wall?

A

Plasmolysed

36
Q

What is plant tissue with Plasmolysed cells called?

A

Flaccid

37
Q

Define active transport.

A

The movement of substances against their concentration gradient across a cell membrane, using ATP and carrier proteins.

38
Q

Define endocytosis.

A

Bulk transport of molecules, too large to pass through a cell membrane even via channel or carrier proteins, into a cell.

39
Q

Define exocytosis.

A

Bulk transport of molecules, too large to pass through a cell membrane even via channel or carrier proteins, out of a cell.

40
Q

What ions are actively transported?

A

Sodium and potassium ions.

41
Q

How many sodium ions bind to the site on active transport?

A

3

42
Q

What is ATP hydrolysed to form?

A

ADP + P

43
Q

How many potassium ions bind to their site with active transport?

A

2

44
Q

What is phagocytosis?

A

When one cell engulfs another.

45
Q

What is pino(endo)cytosis?

A

Cells ingesting liquids.

46
Q

Is ATP needed for endocytosis?

A

Yes, to move vesicles using molecular motor proteins along cytoskeleton threads.

47
Q

What determines membrane fluidity at cold temperatures?

A

The proportions of unsaturated and saturated fatty acids within a cell membrane.

48
Q

What also buffers the effect of lowered temperature?

A

Cholesterol prevents phospholipid molecules from packing together too closely.

49
Q

How do solvents, such as acetone and ethanol, damage membranes?

A

They dissolve lipids.

50
Q

What is broken by strong reducing agents?

A

Disulfide bonds.

51
Q

Roles of membranes

A
  • partially permeable barriers between the cell and its environment, between organelles and the cytoplasm and within organelles
  • sites of chemical reactions
  • sites of cell communication (cell signalling).
52
Q

What is cell signalling?

A

communication between cells

53
Q

Why can’t water soluble substance pass through the membrane?

A

The centre of the bilayer is hydrophobic

54
Q

Functions of membranes within cells

A

Forms vesicles
Isolation of ontents from cytoplasm
Site of processes/ reaction
Surface for attachment (of enzymes/ribosomes)
Control what substances enter and leave organelles- selective permeability
Creation of concentration gradients

55
Q

Functions of membranes within cells

A

Forms vesicles
Isolation of ontents from cytoplasm
Site of processes/ reaction
Surface for attachment (of enzymes/ribosomes)
Control what substances enter and leave organelles- selective permeability
Creation of concentration gradients

56
Q

What molecule can easily pass through the phospholipid bilayer?

A

fat-soluble substances

57
Q

What membranes do not have cholesterol?

A

Bacterial membranes

58
Q

What is the function of glycolipids and glycoproteins?

A
  • stabilise the membrane by forming hydrogen bonds with surrounding water molecules
  • where drugs, hormones and antibodies bind
  • receptors for cell signalling
  • antigens
59
Q

Describe the role of membrane bound receptors

A
  • proteins
  • specific shapes
  • drugs use them to trigger a response from the cell or block the receptor and prevent it from working
60
Q

How can you investigate factors affecting membrane fluidity?

A

BEETROOT

  • cut five pieces and rinse
  • place in test tubes containing water
  • different temperatures for known time
  • remove beetroot, leaving coloured water
  • colorimeter
  • higher permeability = more pigment released = more absorbance
61
Q

How does temperature affect membrane permeability?

A
  • <0 degrees, packed together, proteins deform, memrbane more permable, ice crystals may form + pierce membrane
  • 0-45 degrees - can move around and arnt packed = partially permeable
  • > 0 bilayer breaks down, water expands inside and puts pressure, proteins deform
62
Q

How does changing the solvent affect membrane permeability?

A
  • ethanol dissolves lipids so increases
63
Q

How can you investigate diffusion in model cells?

A

1) make agar jelly with phenolphthalein and dilute sodium hydroxide (it will be a LOVELY shade of pink)
2) fill beaker with dilute HCl
3) Cut cubes of jelly and put them in the acid
4) the cubes will go colourless

64
Q

How can you investigate water potential in the lab?

A

POTATO

  • different conc sucrose solutions
  • put potato in and weigh
  • calculate % change in mass
65
Q

What molecules do facilitated diffusion?

A

polar and charged
carbohydrates
amino acids
ions

66
Q

Examples of hydrophobic molecules that can enter membranes?

A

O2
CO2
N2
steroids

67
Q

Examples of small uncharged polar molecules that can enter membranes

A

H2O
glycerol
urea
ethanol

68
Q

Examples of large uncharged polar molecules that cant enter membranes

A

glucose and sucrose

Biology AS Rafa (13 decks)

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