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IGCSE - Biology > Movement of substances in and out of cells > Flashcards

Movement of substances in and out of cells Flashcards

1
Q

What are the three movements of substances in and out of cells?

A
  • Diffusion
  • Osmosis
  • Active transport
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2
Q

What is diffusion?

A

The net movement of particles from an area of high concentration to an area of lower concentration until a uniform concentration is achieved

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3
Q

Why does diffusion happen in both liquids and gases but not solids?

A

The particles in these substances are free to move randomly

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4
Q

The bigger the different in concentration in diffusion….

A

The faster the rate of diffusion

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5
Q

What type of molecules can diffuse through cell membranes?

A

Small molecules like glucose, amino acids, water and oxygen. Big molecules like starch and protein cant fit through!

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6
Q

Particles in a cell membrane move from an area of…

A

Higher concentration to an area of lower concentration

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7
Q

If there are more particles on one side of the membrane…

A

Theres a net movement from that side

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8
Q

What is osmosis?

A

The net movement of water molecules across a partially permeable membrane from a region of higher water concentration to an area of lower concentration until a uniform water concentration is achieved.

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9
Q

Is osmosis a type of diffusion?

A

Yes

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10
Q

What is a partially permeable membrane?

A

A membrane with lots of very small holes in it - stops big molecules flowing through

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11
Q

Why can water molecules flow both ways through the membrane is osmosis?

A

Because the water molecules move around randomly all the time

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12
Q

If there is a net flow of water into a region with fewer water molecules in osmosis…

A

That solution becomes more dilute as the water tries to even up the concentration on both sides

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13
Q

What does the tissue fluid around our cells contain?

A

Water, oxygen and glucose that is squeezed out of the blood capillaries to supply the cell with everything they need.

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14
Q

Why is the concentration in a tissue fluid different to the fluid outside the cell?

A

So water can move into the cell from the tissue fluid, or out of the cell by osmosis

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15
Q

If a cell is short of water…

A

It becomes concentrated - the solution outside is more dilute so water moves into the cell by osmosis

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16
Q

If a cell has lots of water…

A

The solution inside is more dilute - water is drawn out of the cell into the fluid outside by osmosis

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17
Q

What are plants supported by?

A

Turgid cells

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18
Q

When a plant is well watered…

A

The cells will draw water in by osmosis, and become plump and swollen (turgid)

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19
Q

What is turgid pressure?

A

The contents of the cell pushing against the cell wall supporting the plant tissue

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20
Q

What happens to a plant if theres no water in the soil?

A

The plant starts to wilt (droop) - the cells loose water therefore loose turgid pressure making them flaccid

21
Q

Why doesn’t a plant totally lose its shape when it becomes flaccid?

A

The inelastic cell wall keeps things in position - it droops just a bit

22
Q

What are plants supported by?

A

Turgid cells

23
Q

When a plant is well watered…

A

The cells will draw water in by osmosis, and become plump and swollen (turgid)

24
Q

What is turgid pressure?

A

The contents of the cell pushing against the cell wall supporting the plant tissue

25
Q

What happens to a plant if theres no water in the soil?

A

The plant starts to wilt (droop) - the cells loose water therefore loose turgid pressure making them flaccid

26
Q

Why doesn’t a plant totally lose its shape when it becomes flaccid?

A

The inelastic cell wall keeps things in position - it droops just a bit

27
Q

What can you use to investigate diffusion in a non-living system?

A

Phenolphthalein - pH indicator. It is pink in alkaline solutions and colourless in acidic solutions and can be used with agar jelly

28
Q

What is the method in the experiment for using the agar jelly?

A
  • Make up agar jelly with phenolphthalein and dilute sodium hydroxide - jelly turns pink.
  • Fill a beaker up with some dilute hydrochloric acid and cut out cubes using a scalpel.
  • Put them into beaker of acid
29
Q

What happens if you leave the agar cubes in the water for a while?

A

They eventually turn colourless as the acid diffuses into the agar jelly and neutralises the sodium hydroxide

30
Q

How can you investigate the rate of diffusion with the agar jelly?

A

Change size of cubes - largest SA:VR will lose colour the quickest

31
Q

How can you investigate osmosis in a living system?

A

Use potato cylinders

32
Q

What is the method for using potato cylinders to investigate osmosis?

A
  • Cut potatoes into equal cylinders
  • Get two beakers: one should be very concentrated sugar solution and the other pure water
  • Measure length of cylinders then leave for half an hour/an hour
  • Measure length after time and compare the start and end results
33
Q

If the cylinders have drawn water in by osmosis…

A

They should be a bit longer

34
Q

If the cylinders have drawn water out…

A

They should have drunk a bit

35
Q

How can you investigate osmosis in a non-living system?

A

Use visking tube

36
Q

What is the method for the visking tube investigating osmosis?

A
  • Tie one end of the visking tube and in the other put a glass tube in it
  • Pour sugar solution down tube
  • Put visking tube in pure water - measure where sugar solution comes up to on the glass tube
  • Leave tube overnight and measure where liquid is on glass tube
37
Q

Water should be drawn into the visking tube…

A

By osmosis - it will force liquid up the glass tube

38
Q

What does the visking tube act as?

A

A partially permeable membrane

39
Q

What is active transport?

A

The movement of particles against a concentration gradient from an area of lower concentration to an area of higher concentration using energy released during respiration

40
Q

Give an example of when active transport is used in the body

A

In our digestive system - there is a low concentration of nutrients in the gut but a high concentration of nutrients in the blood

41
Q

If the concentration gradient is wrong…

A

Nutrients go the other way - if they follow the rules of diffusion

42
Q

What does active transport allow?

A

For all the nutrients to be taken in by the blood, despite the concentration gradient being the wrong way. It is essential to stop us from starving

43
Q

How do plants use active transport?

A

They get minerals from the soil (lower concentration) into the root hair cells (higher concentration)

44
Q

What three main factors affect the movement of substances?

A
  • SA:VR
  • Temperature
  • Concentration gradient
45
Q

Is the rate of diffusion in diffusion, osmosis and active transport higher or lower in cells with a larger SA:VR?

A

Higher

46
Q

Does a smaller cube have a larger or smaller SA:VR? And does it affect the rate of movement?

A

Larger SA:VR meaning that substances move in and out the cube faster

47
Q

As temperature increases…

A

Substances move in and out of cells faster because they get warmer so have more energy and move faster

48
Q

If there is a big difference in concentration gradient…

A

Substances move in and out faster between the inside and outside of the cell.

49
Q

Does a big difference in concentration gradient affect active transport?

A

No becuase active transport is against its concentration gradient

IGCSE - Biology (20 decks)

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