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BGS Bio AS1 > U1T5 - Cell Physiology > Flashcards

U1T5 - Cell Physiology Flashcards

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Biology 101 flashcards
1
Q

What are all living cells surrounded by?

What are they bathed in?

A

Water.

Tissue Fluid.

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2
Q

Where does the energy for diffusion come from?

A

Kinetic energy of the particles.

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3
Q

What affects the rate of diffusion?

A

Concentration gradient, size of particles, thickness of membrane, surface area + temperature.

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4
Q

How might you summarise Fick’s law?

A

Rate of diffusion Is proportional to: (surface area x difference in concentration) / length of diffusion pathway.

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5
Q

What substances will simple diffusion allow to pass through?

A

Non polar substances (hydrophobic, fat soluble) + small molecules e.g. Vitamins ADEK, O2, CO2 in solution and water.

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6
Q

Where do substances diffuse through in simple diffusion?

A

Spaces in the phospholipid bilayer.

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7
Q

Which substances will facilitated diffusion allow to pass through?

A

Water soluble substances (hydrophobic, polar), large molecules. e.g. glucose, amino acids + ions.

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8
Q

How does facilitated diffusion work?

A

Protein carriers matching specific molecules’ binding sites help them to move across the membrane.

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9
Q

What are the 2 types of protein which are used in facilitated diffusion?

A

Carrier proteins + ion (channel) proteins

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10
Q

How do carrier proteins work in facilitated diffusion?

A

Allow larger polar molecules to diffuse across membrane (glucose, amino acids). Protein attaches to particular molecules’ binding site, causing protein to change shape enabling it to deliver molecule through membrane. Number of carriers affects rate of uptake.

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11
Q

How do channel proteins work in facilitated diffusion?

A

Enable polar particles (ions) to pass through. Some are always open whilst some are gated. Gated channels open + close allowing control of ion movement depending on cell needs.

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12
Q

What is the speed difference between facilitated and simple diffusion?

A

Simple diffusion is faster.

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13
Q

What is the natural tendency of ions in terms of movement?

A

They move from high to low concentration.

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14
Q

What molecules can be transported by way of active transport?

A

Highly specific. e.g. glucose, sodium.

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15
Q

What does the cytosol hold?

A

Reserves of molecules valuable to cell’s metabolism. (e.g. nitrate ions in plant root hair cells for amino acids for proteins for plant growth, calcium ions in muscle fibres for muscle contraction + Na+ for nerve impulse transmission)

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16
Q

What happens with reserve ions held in cytosol?

A

Reserves don’t escape. Cell membrane retains them inside cell. When more ions available for uptake, actively absorbed into cell.

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17
Q

What do cells which are involved in active transport need?

A

Many mitochondria (aerobic respiration) + high respiration rate to produce ATP.

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18
Q

What factors affect cells’ ability to perform active transport?

A

Temperature, oxygen concentration + presence of poisons (cyanide).

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19
Q

Why do factors that affect respiration rate affect active transport?
(Temp, o2 conc, poisons)

A

Higher temp, more kinetic energy, more resp, more ATP, more active transport.
More o2, more resp, more ATP, more active transport.
No resp, no ATP, no active transport.

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20
Q

What is cytosis important for transporting?

A

Large molecules which are too big for protein carriers + bulk transport of smaller molecules (water)

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21
Q

What happens during endocytosis?

A

Cell surface membrane invaginates (infolds) around substances entering cell. Forms membrane bound sac/vesicle which pinches off inside of membrane.

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22
Q

What are the 2 types of endocytosis?

A

Phagocytosis + pinocytosis.

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23
Q

How does amoeba get its nutrients?

A

It engulfs its food by phagocytosis. Food is taken into cytoplasm inside food vacuole. Lysosomes release digestive enzymes into vacuole + soluble products absorbed.

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24
Q

How might a human egg cell get its nutrients?

A

Takes up nutrients from surrounding cells by pinocytosis.

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25
Q

What different things can occur by pinocytosis?

A

Movement of lipids between cells + surrounding tissue after digestion of food.

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26
Q

Explain the process of phagocytosis.

A

Solid material taken into cell in vesicle. Lysosomes fuse with vesicle, emptying enzymes inside. Enzymes digest material + products absorbed into cytoplasm.

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27
Q

Why are the digestive enzymes contained within a lysosome?

A

They’re transporting digestive enzymes which could digest valuable substances within cell cytoplasm so must be kept separate.

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28
Q

What is exocytosis important in?

A

Secretion of many cell proteins, including digestive enzymes + hormones.

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29
Q

What do you call a solution with high water conc?

Low water conc?

A

Dilute

Concentrated

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30
Q

What would happen if a bag containing conc sucrose was placed in water?

A

Water molecules move from water into bag as in conc sucrose solution, most water molecules are attracted to dissolved sucrose. Dissolved substance therefore has cloud of polar water molecules around its molecules held by weak hydrogen bonds, these can’t move freely.

31
Q

How can water pass through phospholipid bilayer?

A

Aquaporins, a type of channel protein.

32
Q

What types of substances do water molecules have an effect on?

A

Sugars (Na+), amino acids (K+), polypeptides (Cl-) + proteins (NO3-)

33
Q

How does solution strength compare to number of water molecules?

A

Stronger solution (more solute), larger number of water molecules which are slowed up + held. In very conc solution, water molecules restricted in movement compared to pure water where free to move randomly.

34
Q

How are hydration shells formed?

A

Water molecules clustering around a solute.

35
Q

How does number of hydration shells compare to movement of water molecules?

A

More hydration shells formed by increase in solute conc, less water molecules can move.

36
Q

What substance has the highest water potential + what does this mean?

A

Pure water. Value of 0. Unable to take in any more water by osmosis.

37
Q

What might lower the water potential of a solution?

A

Once a solute has dissolved in the water, the water molecules are less likely to move/diffuse so this lowers potential, making it more negative.

38
Q

True or false:

Solutions always have a positive value of water potential.

A

False. They always have a negative value.

39
Q

The more concentrated a solution, the more ___ its water potential. Why is this?

A

Negative. Water molecules have a lower potential to move.

40
Q

What is water potential measured in?

A

Kilopascals (kPA)

41
Q

Will solute potential be the same as water potential?

A

Not always.

42
Q

True or false:
Solutions always have a negative value of solute potential.
Why?

A

True.
The forces of attraction between the solute molecules + water molecules reduce movement of water molecules (hydration shells)

43
Q

The more solute molecules present, the ___ the water potential.
The ____ solute molecules present, the higher the water potential.

A

Lower.

Fewer.

44
Q

How does pressure in the cell increase?

A

In cytoplasm, water molecules move around at random. Some collide with membrane surrounding membrane and exert pressure on it.

45
Q

What effect does pressure have on the cell?

A

Pressure produced pushes against membrane from inside whilst pressure potential pushes against membrane from outside. These 2 act In opposite directions.

46
Q

True or false:

Pressure potential is always negative.

A

False, it is usually positive, if not 0.

47
Q

What is the equation for water potential?

A

Water potential = solute potential + pressure potential.

48
Q

What might happen if an animal cell is placed in pure water?

A

It would disintegrate from pressure potential generated as they’re easily damaged by changes in external solution due to the lack of cell wall.

49
Q

How do unicellular animals which live in water survive?

A

Surroundings have much higher water potential than cell solution and so contain tiny water pump to avoid lysis.

50
Q

If a cell is placed in a concentrated sugar solution, what might happen + why?

A

Concentration of water molecules inside cell is higher than outside. Water moves out by osmosis from higher to lower water potential outside. Contents shrinks away from cell wall except where adjacent protoplasts are joined by plasmodesmata+ becomes plasmolysed.

51
Q

How is plasmolysis most easily seen?

A

Using a microscope in cells with coloured solution in vacuoles (onion, beetroot). in plasmolysed cell, no pressure potential. As it begins to take up water, contents enlarge. When cytoplasm pushes against wall, slight pressure potential produced. As uptake continues, water potential becomes 0 and It stops.

52
Q

What do plant cells rely on for support?

A

Turgor. Cell wall’s strength limits expansion of cell membrane as water enters plant by osmosis. Opposing forces of cell membrane + wall create turgor.

53
Q

What happens if a plant suffers a shortage of water?

A

Cells cease to be turgid + tissue becomes flaccid. If lots of cells are flaccid, wilting occurs.

54
Q

What are the carrier proteins in active transport referred to as?

A

Pumps

55
Q

What does the relative abundance of different carrier proteins influence in active transport?

A

The relative abundance of different substances able to pass through the membrane.

56
Q

When might plasmolysis occur in nature?

A

Plants growing in field with too much fertiliser, seed from woodland tree growing in salt marsh.

57
Q

On a graph of substance entry rate vs external substance conc, the rate of substance entry levels off, why might this be?

A

This is using facilitated diffusion, it uses carrier proteins to move substances across the membrane. Here, all the proteins are saturated (in use) so the rate levels off.

58
Q

Why might scientists use a control group in an experiment to determine the effectiveness of an antacid tablet?

A

This allows us to compare the normal acid secreted in a certain time period vs those using the tablet.

59
Q

How might a control group have been treated in an experiment testing an antacid tablet?

A

They may have been given a placebo drug which they weren’t told was fake but treated exactly the same as the main group otherwise. This tells us whether the drug simply produces a placebo effect.

60
Q

Why might percentage change in mass be better to se than change in mass?

A

Percentage change will ensure there is no confusion due to different starting weights so we can compare fairly.

61
Q

What happens if you put a plant cell into a hypotonic solution?

A

Water moves into cell by osmosis until it is in equilibrium where water potential is 0. No more water will now enter the cell so the cell is turgid. The influx of water caused the cell to swell and the cytoplasm put pressure on the cell wall, increasing pressure potential.

62
Q

Why might there be a different pressure potentials in 2 cells?

A

They may have more internal pressure due to water molecules pushing against membrane so it’s more turgid + full of water.

63
Q

When a plant cell has a pressure potential of 0, what is the term used?

A

Plasmolysed.

64
Q

What is the weighing method?

A

Weigh the substance on a mass balance, add to sucrose solution, surface dry + calculate percentage change.

65
Q

What might the addition of solutes to a solution cause?

A

Lower solute potential due to restriction of movement of free water molecules + creating hydration shells so water potential is decreased.

66
Q

In terms of water potential, what effect do hydration shells have?

A

They lower the water potential of a solution.

67
Q

In animal cells, what contributes to water potential?

A

Dissolved solutes.

68
Q

What creates pressure potential in plant cells?

A

The presence of the cell wall.

69
Q

When a cell is plasmolysed, can it recover?

A

Yes, if it can gain water.

70
Q

When drawing a diagram of a plasmolysed cell, what should you include?

A

Vacuole, cell wall, cell membrane, plasmodesmata.

71
Q

If a single celled organism is placed in a freshwater environment, and it takes in water, how does the water potential inside the cell compare to outside?

A

It has a lower water potential inside the cell.

72
Q

What might reduce the light passing through onion tissue when viewed under a microscope?

A

Diaphragm, dimmer switch or staining with iodine.

73
Q

Why might there be chloroplasts clumped in the centre of a plasmolysed cell?

A

Vacuole/cytoplasm has shrunk.

74
Q

What causes the change in shape of the plates during closure of a trap which has water moving into it?

A

Cells of lower mesophyll become more turgid + lower mesophyll increases in size + becomes more convex.

BGS Bio AS1 (14 decks)

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