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Biology > Transport across Membranes > Flashcards

Transport across Membranes Flashcards

1
Q

Define the term “simple diffusion”. (F)

A

Diffusion across a plasma membrane without the aid of membrane proteins.

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2
Q

Define the term “osmosis”. (F)

A

Diffusion of water through a partially permeable membrane down a water potential gradient. A passive process.

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3
Q

Define the term “passive transport”. (F)

A

Transport that is a passive process (does not require energy) and does not use energy from cellular respiration.

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4
Q

Define the term “active transport”. (F)

A

Movement of particles across a plasma membrane against a concentration gradient. Energy is required.

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5
Q

Define the term “endocytosis”. (F)

A

The bulk transport of materials into cells via invagination of the cell-surface membrane forming a vesicle.

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6
Q

Define the term “exocytosis”. (F)

A

The bulk transport of materials out of cells. Vesicles containing the material fuse with the cell-surface membrane and the contents are released to the outside of the cell.

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7
Q

Define the term “pinocytosis”. (F)

A

Endocytosis of liquid materials.

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8
Q

Define the term “phagocytosis”. (F)

A

Process by which white blood cells called phagocytes recognise non-self cells, engulf them and digest them within a vesicle called a phaolysosome.

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9
Q

Define the term “phagocytosis”. (F)

A

Endocytosis of solid materials.

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10
Q

Explain the difference between a channel protein and a carrier protein and link this to their functions

A
  • channel proteins provide a hydrophilic channel for passive diffusion of polar molecules and ions
  • carrier proteins change shape with ATP for active transport of molecules
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11
Q

Explain the importance of the structure of ATP in active transport.

A
  • hydrolysed into ADP and phosphate
  • phosphate molecule binds to carrier protein
  • carrier protein changes shape
  • phosphate molecule released from carrier protein and recombines with ADP to form ATP
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12
Q

List the factors affecting the rate of diffusion of a molecule. (F)

A
  • temperature
  • concentration difference
  • distance
  • surface area
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13
Q

Explain how substances can move across a membrane by simple diffusion.

A
  • particles have kinetic energy
  • particles can pass through phospholipid bilayer
  • move down the concentration gradient due to random movement of particles
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14
Q

State which types of molecule can move across a membrane by simple diffusion. (F)

A
  • small non-polar molecules

- small polar molecules

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15
Q

Explain how substances can move across a membrane by facilitated diffusion (include protein specificity). (F)

A
  • membranes contain channel proteins
  • hydrophilic so allow polar molecules and ions to pass through
  • down the concentration gradient and passive
  • limited by number of channel proteins present
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16
Q

Explain how substances can move across a membrane by active transport (include protein specificity). (F)

A
  • membranes contain carrier proteins
  • can transport molecules that can bind to its receptors
  • against concentration gradient
  • ATP binds to carrier protein and is hydrolysed
  • phosphate molecule binds to protein to make it change shape
  • molecule is released
  • phosphate ion recombines with ADP to form ATP
  • carrier protein returns to original shape
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17
Q

Explain how substances can move into a cell by endocytosis (using phagocytosis as an example). (F)

A
  • cell surface membrane invaginates when it comes into contact with pathogen
  • membrane enfolds material until membrane fuses to form a vesicle
  • vesicle pinches off and moves into cytoplasm
  • binds with lysosomes to form a phagolysosome to digest the pathogen
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18
Q

Explain how substances can move out of a cell by exocytosis (using secretion as an example). (F)

A
  • vesicles, usually formed by the Golgi apparatus, move to cell surface membrane
  • fuse with cell surface membrane
  • vesicle contents released outside of the cell
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19
Q

Identify which transport mechanisms require an input of energy from ATP. (F)

A
  • active transport
  • exocytosis
  • endocytosis
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20
Q

Explain why it is easier for an oxygen molecule to diffuse across a membrane than a water molecule.

A
  • oxygen molecule is non-polar
  • water molecule is polar
  • core of phospholipid bilayer is hydrophobic
  • oxygen molecule is not repelled by the core
  • water molecule is repelled by the core
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21
Q

Explain why steroid hormones can easily cross a membrane by simple diffusion.

A
  • lipid derived
  • soluble in lipids
  • phospholipid bilayer is predominantly lipid
  • pass through easily
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22
Q

Explain why ions are only able to cross a membrane through a protein channel.

A
  • small molecules but have a significant charge
  • repelled by hydrophobic core of phospholipid bilayer
  • protein channel is hydrophilic
  • not repelled by protein channel
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23
Q

Describe how to carry out an investigation to investigate how the rate of diffusion is affected by surface area.

A
  • agar with phenolphthalein that turns pink in presence of alkali
  • cut into different sized blocks
  • immerse in solution of sodium hydroxide for 10 minutes
  • remove blocks and measure diffusion distance with a ruler
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24
Q

Describe and explain the results you would expect to see in an investigation into how the rate of diffusion is affected by surface area.

A

The larger the surface area, the faster the rate of diffusion.

More exchange surface available for diffusion to take place.

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25
Q

Describe how to carry out an experiment to investigate how the rate of diffusion is affected by temperature.

A
  • dialysis tubing
  • tie one end of section of tubing
  • fill with solution (starch and glucose) and tie the other end
  • place into a boiling tube with distilled water
  • place into water baths at different temperatures
  • test for presence of glucose in water
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26
Q

Describe and explain the results you would expect to see in an investigation into how the rate of diffusion is affected by temperature.

A

The higher the temperature, the faster the rate of diffusion.

  • molecules have more kinetic energy
  • move at higher speeds
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27
Q

Define the terms “solvent”. (F

A

A liquid in which substances are dissolved.

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28
Q

Define the terms “solute”. (F

A

A substance dissolved in a solvent.

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29
Q

Define the terms “solution”. (F

A

A substance formed from a solute dissolving in a solution.

30
Q

Define the term “water potential”. (F)

A

Measure of the quantity of water compared to solutes, measured as the pressure created by the water molecules in kilopascals (kPa)

31
Q

State the symbol for water potential. (F)

A

Ψ

32
Q

State the water potential of pure water. (F)

A

0kPa

33
Q

Explain why water potential cannot have a positive value. (F)

A

Pure water is 0kPa, which is the highest possible value, as the presence of solute in water lowers the water potential below zero.

34
Q

Define the term “water potential gradient”. (F)

A

The difference in water potential between two regions.

35
Q

Define the term “net movement of water”. (F)

A

The overall movement of water molecules from one area to another,

36
Q

Describe the effect of a hypertonic solution on an animal cell, including a description of the relative water potentials, osmosis and the overall effect on the cell. (F)

A
  • water potential of solution is lower than cell
  • net movement of water leaves cell
  • cell shrinks and shrivels
37
Q

Describe the effect of a isotonic solution on an animal cell, including a description of the relative water potentials, osmosis and the overall effect on the cell. (F)

A
  • water potential of solution is same as cell
  • net movement of water in and out at equal rates
  • no change on cell (normal)
38
Q

Describe the effect of a hypotonic solution on an animal cell, including a description of the relative water potentials, osmosis and the overall effect on the cell. (F)

A
  • water potential of solution is higher than cell
  • net movement of water enters cell
  • cell swells and bursts, releasing cellular contents
39
Q

Describe the effect of a hypertonic solution on a plant cell, including a description of the relative water potentials, osmosis and the overall effect on the cell. (F)

A
  • water potential of solution is lower than cell
  • net movement of water leaves cell
  • plasmolysis and contents shrink, so the protoplast pulls away from the cell wall
40
Q

Describe the effect of a isotonic solution on a plant cell, including a description of the relative water potentials, osmosis and the overall effect on the cell. (F)

A
  • water potential of solution is same as cell
  • net movement of water in and out at equal rates
  • protoplast begins to pull away from the cell wall
41
Q

Describe the effect of a hypotonic solution on a plant cell, including a description of the relative water potentials, osmosis and the overall effect on the cell. (F)

A
  • water potential of solution is higher than cell
  • net movement of water enters cell
  • the protoplast swells and becomes turgid (normal)
42
Q

Define the term “hypertonic”.

A

When an external solution has a more negative/lower water potential than the water potential of the cell solution.

43
Q

Define the term “hypotonic”.

A

When an external solution has a less negative/higher water potential than the water potential of the cell solution.

44
Q

Define the term “cytolysis”.

A

The bursting of an animal cell caused by increasing hydrostatic pressure as water enters by osmosis.

45
Q

Define the term “plasmolysis”.

A

The pulling away of the cytoplasm and plasma membrane from the cell wall due to lack of water.

46
Q

Define the term “protoplast”.

A

The whole plant cell excluding the cell wall.

47
Q

Define the term “turgid”.

A

Plant cells that are swollen due to water entry by osmosis.

48
Q

Define the term “haemolysis”.

A

The bursting or rupture of a red blood cell.

49
Q

Describe how to carry out an experiment to investigate the effects of solutions of different water potential on plant cells.

A
  • cut out some pieces of potato of the same size
  • weigh and record mass
  • place in sugar solutions of different concentrations
  • leave in for 5 minutes and weigh
  • calculate mass change
50
Q

Describe and explain the results you would expect to see from an experiment to investigate the effects of solutions of different water potential on plant cells.

A

Where there is no mass change, the solution is isotonic to the plant cells.

When the mass increases, the solution is hypotonic to the plant cells.

When the mass decreases, the solution is hypertonic to the plant cells.

51
Q

Describe how to carry out an experiment to investigate the effects of solutions of different water potential on plant and animal cells.

A
  • hard boil an egg
  • weigh and record mass
  • place in different concentrations of sugar syrup for 5 minutes
  • record final weight and calculate mass change
52
Q

Describe and explain the results you would expect to see from an experiment to investigate the effects of solutions of different water potential on animal cells.

A

Where there is no mass change, the solution is isotonic to the animal cells.

When the mass increases, the solution is hypotonic to the animal cells.

When the mass decreases, the solution is animal to the plant cells.

53
Q

Describe the meaning of the symbol =

A

Equals

54
Q

Describe the meaning of the symbol

A

Lesser than

55
Q

Describe the meaning of the symbol <

A

Significantly lesser than

56
Q

Describe the meaning of the symbol&raquo_space;

A

Greater than

57
Q

Describe the meaning of the symbol >

A

Significantly greater than

58
Q

Explain why plant cells don’t burst by osmosis.

A
  • strong cellulose walls
  • when water enters, increased hydrostatic pressure pushes membrane against cell walls (turgor)
  • as turgor pressure increases it resists the entry of further water
59
Q

Write an equation to link the water potential of a cell with its pressure potential and its solute potential.

A

water potential = pressure potential x solute potential

60
Q

Define the term by “absolute uncertainty”.

A

The extent by which the measurement could be out

61
Q

State the equation for a straight line.

A

y = mx + c

62
Q

Describe how to find where a straight line intercepts the x-axis both from a graph and from the equation for the straight line.

A
  • the value where the line intercepts the horizontal line

- set y = 0 and solve the equation

63
Q

Define the term “relative uncertainty or percentage error”.

A

A measure of how inaccurate a measurement could be standardised for it’s size.

64
Q

Explain how to calculate the percentage error of a measurement (and when data are combined e.g. to obtain data on the change of a particular value over time).

A

absolute uncertainty of measurement/measurement x 100%

65
Q

Define the term “precision” in relation to experimental design and scientific equipment.

A

The closeness of agreement between independent measurements obtained under the same conditions.

66
Q

Define the term “accuracy” in relation to experimental design and scientific equipment.

A

The measure of the closeness of agreement between an individual test result and the true value.

67
Q

Define the term “repeatability” in relation to experimental design and scientific equipment.

A

The precision obtained when measurement results are produced over a short timescale by one person using the same equipment in the same place.

68
Q

Define the term “reproducibility” in relation to experimental design and scientific equipment.

A

The precision obtained when measurement results are produced over a wider timescale by different people using equivalent equipment in different but equivalent places.

69
Q

Define the term “resolution” in relation to experimental design and scientific equipment.

A

The smallest change in quantity being measured that can be detected by an instrument.

70
Q

Define the term “validity” in relation to experimental design and scientific equipment.

A

It measures what it is supposed to be measuring. an investigation procedure is valid if it is suitable to answer the question being asked.

71
Q

Define the term “validity” in relation to experimental design and scientific equipment.

A

It measures what it is supposed to be measuring. An investigation procedure is valid if it is suitable to answer the question being asked.

Biology (23 decks)

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