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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

diffusion

A

net random movement of substances from an area of high to low concentration

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2
Q

osmosis

A

net random movement of water from an area of high to low water potential across a partially permeable membrane

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3
Q

active transport

A

movement of substances from an area of low to high concentration, using energy from ATP

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4
Q

What is the function of the transport system in plants?

A

leaves can receive water and
mineral ions, both for photosynthesis

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5
Q

What is the xylem?

A

tissue that transports water and mineral ions from the roots to the leaves

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6
Q

Describe the structure of the xylem

A
  • made of thick walled dead cells without any cytoplasm
  • cell wall with lignin
  • upwards movement
  • no end walls
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7
Q

Why doesn’t the xylem have organelles?

A

to prevent obstruction to flow of water and minerals

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8
Q

Why does the xylem have cell walls stiffened with lignin?

A

waterproof
strength
stops cell collapsing in

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9
Q

Why doesn’t the xylem have end walls?

A

cells join together form long tubes to make complete tissue

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10
Q

Give examples of mineral ions needed for photosynthesis

A

magnesium ions
nitrate ions

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11
Q

What is the use of magnesium ions in plants?

A

make chlorophyll for photosynthesis

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12
Q

What is the use of nitrate ions in plants?

A

make amino acids and proteins

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13
Q

What is the phloem?

A

tissue in plants that transports sugars and amino acids both up and down the plant from the leaves to respiring tissues

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14
Q

translocation

A

movement of sugars and amino acids through the phloem that uses energy

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15
Q

Describe the structure of the phloem

A
  • companion cells
  • sieve plates (thin layer of cytoplasm)
  • cell walls of cellulose
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16
Q

Why does the phloem have companion cells?

A

keeps phloem alive
has ribosomes and cytoplasm to do this

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17
Q

Why does the phloem have sieve plates?

A

allows contents to flow through

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18
Q

How does translocation work?

A
  • companion cells have mitochondria
  • sucrose moved into sieve tubes by active transport
  • low water potential in sieve tubes
  • water moves via osmosis into sieve tubes
  • high pressure created
  • sucrose and water removed from phloem
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19
Q

Why is translocation called an active process?

A

energy needed

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20
Q

Why is the process of translocation so important?

A

sugars needed in growing points
- roots
- leaves

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21
Q

How is water transported around the plant?

A
  • enters by root hair cells
  • high surface areas
  • short diffusion distance
  • water potential outside plant is higher than inside cells
  • via osmosis
  • water moves from cell to cell down concentration gradient
  • via osmosis
  • water reaches xylem vessel - carried to all parts of plant
22
Q

How are mineral ions transported around the plant?

A
  • enters by root hair cells
  • concentration of the solutes outside is lower than inside
  • move into the roots from the soil
  • via active transport
  • reaches phloem vessel
  • carried to all part of plant
23
Q

Which direction does the water and mineral ions move in the xylem?

A

upwards towards leaves

24
Q

Which direction do the amino acids and proteins move in the phloem?

A

upwards and downwards to leaves and roots

25
Q

transpiration

A

water loss via evaporation through the stomata

26
Q

What is the transpiration stream?

A

upwards movement of water through the xylem from roots to leaves

27
Q

What are the functions of the transpiration stream?

A
  • carry mineral ions
  • keep turgor pressure high
  • supplies water
  • evaporation cools leaf
28
Q

Describe the process of transpiration

A
  • water leaves
    cells of the mesophyll
  • evaporates
    into air spaces in
    spongy mesophyll
  • water diffuses out through stomata
  • loss of water from mesophyll cells
    makes lower
    water potential
  • water moves into them by osmosis
  • water leaves xylem to replace water lost
29
Q

How does temperature affect transpiration?

A
  • increase in kinetic energy
  • faster rate at higher temps
  • more transpiration
30
Q

How does light intensity affect transpiration?

A
  • more light
  • more photosynthesis
  • more co2 needed
  • stomata open
  • more transpiration
31
Q

How does wind speed affect transpiration?

A
  • water molecules blown away faster
  • higher water potential in leaf
  • more transpiration
32
Q

How does humidity affect transpiration?

A

transpiration increases when humidity decreases
due to concentration gradient

33
Q

How does water supply affect transpiration?

A

lower water supply is caused by more transpiration than supply
- plant wilts
- guard cells around stomata become turgid - stops transpiration

34
Q

What is an isotonic solution?

A

solution outside cell has same water potential as inside cell - no net movement

35
Q

What is a hypertonic solution?

A

solution outside cell has lower water potential then inside cell - net movement of water molecules out of cell

36
Q

What is a hypotonic solution?

A

solution outside cell has higher water potential then inside cell - net movement of water molecules into cell

37
Q

What happens to an animal cell in an hypotonic solution?

A

lysed
bursts - no cell wall

38
Q

What happens to plant cell in an hypotonic solution?

A

turgid (normal)

39
Q

What happens to an animal cell in an isotonic solution?

A

normal

40
Q

What happens to a plant cell in an isotonic solution?

A

flaccid

41
Q

What happens to an animal cell in an hypertonic solution?

A

shrivels

42
Q

What happens to a plant cell in an hypertonic solution?

A

plasmolyzed
wilts - not enough water to fill cells
- cytoplasm shrinks

43
Q

What are the stomata?

A

holes in the surface of the leaf, mainly on bottom

44
Q

What is the function of the stomata?

A

gas exchange
CO2 in (photosynthesis)
O2 out (respiration)

45
Q

What is the function of the guard cells in relation to stomata?

A

control the opening and closing of stomata
two guard cells on either side of a stomata

46
Q

Describe the structure of a guard cell

A

thickened, inflexible inner cell wall

47
Q

How do guard cells complete the function in relation to stomata?

A
  • photosynthesise in light
  • concentration of sugars increases
  • water potential in guard cells lowers
  • water moves into guard cells
  • via osmosis
  • become turgid and stomata open
    (opposite to close ; dark etc.)
48
Q

What is a potometer?

A

device used to measure rate of transpiration

49
Q

How do you set up a potometer?

A
  • cut stem of shoot
  • put shoot stem into bung
  • put bung into potometer
  • make sure tap is closed and is full of water (no bubbles)
  • lift potometer out of water
  • leave end of capillary tube out of water until air bubble forms then put end
    into beaker of water
  • measure transpiration rate as distance bubble travels in five minutes
50
Q

What are some things to ensure when setting up a potometer?

A
  • potometer set up under water - prevents air bubbles from entering
    system and blocking xylem
  • grease joint with petroleum jelly - this prevents
    water loss and air entry
  • take multiple readings to find average

iGCSE Biology (20 decks)

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