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biology gcse > topic 6 - plant structures and their functions > Flashcards

topic 6 - plant structures and their functions Flashcards

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1
Q

is photosynthesis exothermic or endothermic?

A

endothermic

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2
Q

what are the main producers of food?

A

algae and plants

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3
Q

what are the algae and plants also the primary producers off in food webs/chains?

A

biomass

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4
Q

where is light energy transferred to in plants?

A

chloroplasts in leaves

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5
Q

what is the photosynthesis word equation?

A

carbon dioxide + water -light-> glucose + oxygen

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6
Q

what is the photosynthesis symbol equation?

A

6CO2 + 6H2O —-> C6H12O6 + 6O2

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7
Q

what are the 3 limiting factors which affect the rate of photosynthesis?

A

CO2 concentration, light intensity and temperature

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8
Q

how does temperature affect the rate of photosynthesis?

A
  • if too low - rate is slow as far from enzymes optimum
  • if is at optimum rate will be fast
  • if above optimum the enzymes active site denatures
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9
Q

how does light intensity affect the rate of photosynthesis?

A
  • as light intensity increases, as does the rate, as more light can be used in photosynthesis.
  • the graph (with rate against light intensity) will then flatten out - even as light intensity increases, rate won’t, as temperature or CO2 concentration must be the new limiting factor.
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10
Q

how does carbon dioxide concentration affect the rate of photosynthesis?

A
  • CO2 concentration increases, as does rate, - until a limiting factor interferes
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10
Q

what is the light intensity equation?

A

= 1/(distance from light)^2

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10
Q

what is a limiting factor?

A

factor that means the rate of photosynthesis will increase with one factor until another limiting factor gets involved in photosynthesis

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10
Q

what apparatus is needed to investigate light intensity’s effect on photosynthesis?

A

need sealed 100ml flask with water at room temp, gas syringe, pondweed, small lamp and ruler

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10
Q

what is light intensity directly proportional to?

A

rate of photosynthesis

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11
Q

what is the method for the core practical to investigate light intensity’s effect on photosynthesis?

A
  1. use ruler to place flask + pondweed 15cm from lamp
  2. leave for around 15 mins
  3. connect gas syringe to flask + record change in volume
  4. move lamp further away and see change in volume
  5. repeat
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12
Q

why is light intensity directly proportional to the rate of photosynthesis?

A

more photons hit the chloroplasts in leaf so more photosynthesis can occur at once

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13
Q

what is the rate of photosynthesis inversely proportional to?

A

distance from the light source

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14
Q

what is the inverse square law?

A

light intensity = 1 ÷ (d)^2

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15
Q

what are root hair cells specialised to do?

A

take up water by osmosis and mineral ions by active transport from the soil as found in root tips

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16
Q

how are root hair cells adapted?

A
  • large surface area due to root hairs - more water can move in
  • large permanent vacuole - affects speed of movement
  • lots of mitochondria provide energy for active transport
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17
Q

what does xylem do?

A

transports water and minerals from roots to shoots

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18
Q

what does phloem do?

A

transports products of photosynthesis (food) to all parts of plant

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19
Q

how are xylem adapted to their function?

A
  • lignin deposited causing them to die
    (lignified)
  • become hollow + joined end-to-end to form continuous tube
  • lignin deposited in spirals = helps cell withstand pressure
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20
Q

how are phloem adapted to their function?

A
  • sieve plates - when break down allowing movement of substances
  • alive
  • energy supplied by mitochondria of companion cells
  • use energy to transport sucrose
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21
Q

how are water and mineral ions transported through the plant?

A

via transpiration through the stomata

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22
Q

what is transpiration?

A

loss of water from leaves and stems of the plants
-> consequence of gas exchange

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23
Q

what is translocation?

A

movement of food substances (eg sucrose) made in leaves up or down phloem for use or storage

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24
Q

where does translocation ONLY occur?

A

phloem

25
Q

how does translocation occur?

A

from sources (where its made) to the sinks (where its used)
-> can depend on season

26
Q

what are stomata?

A

small openings on a leaf where oxygen, carbon dioxide and water can move/exchange

27
Q

how are stomata adapted in leaves?

A

able to close to minimise water loss and open to increase evaporation

28
Q

what are guard cells?

A

cells that open and close the stomata

29
Q

describe guard cells

A
  • kidney shaped
  • thin outer walls and thick inner walls
  • light sensitive
30
Q

what do guard cells do when lots of water is available?

A

cells fill and change shape - open stomata and allow gases to be exchanged and more water to leave the plant

31
Q

where is most stomata found?

A

bottom of leaf, allowing gases to be exchanged which minimising water loss by evaporation

32
Q

how are chlorophyll adapted in leaves?

A

green = most efficient colour for absorbing light

33
Q

why are leaves thin?

A

so CO2 has a short diffusion distance to enter leave and O2 has a short diffusion distance to exit

34
Q

why do leaves have large surface areas?

A

means leaf can absorb more light at once maximising rate of photosynthesis

35
Q

what environmental factors affect the rate of water uptake?

A
  • temperature increase
  • increase in humidity
  • increase in air movement
  • increase in light intensity
36
Q

how does temperature affect the rate of water uptake?

A
  • increase means molecules move faster and evaporation occurs at a faster rate
  • increases rate of photosynthesis and more stomata is open so water evaporates more
37
Q

how does an increase in humidity affect rate of water uptake?

A
  • if high then the concentration gradient is reduced between concentration of water vapour inside and outside the leaf
38
Q

how does an increase in air movement affect rate of water uptake?

A
  • more air moving from leaf means concentration of water surrounding leaf will be lower
  • steeper concentration gradient
39
Q

how does an increase in light intensity affect rate of water uptake?

A
  • increased rate of photosynthesis so more stomata open
40
Q

how do you do the rate calculations for transpiration?

A

using a potometer and measuring how far the bubble moves in capillary tube

41
Q

how does extreme environments affect the cuticle?

A

many leaves have a waxy cuticle on top = preventing evaporation of water when water is scarce

42
Q

how does extreme environments affect leaves stomata?

A

can close to prevent evaporation of water or opened when CO2 is needed for photosynthesis

43
Q

what is a phototropism?

A

response to light

44
Q

what is a gravitropism?

A

response to gravity

45
Q

what do auxins stimulate?

A

growth of shoots by cell elongation

46
Q

what do auxins do to growth in the roots and shoots?

A

shoots = promote growth
roots = inhibit growth

47
Q

where are auxins produced?

A
  • tips of shoots and roots
  • diffuse backwards to stimulate cell elongation
48
Q

are shoots positively or negatively phototropic?

A

positively - grow towards light

49
Q

what happens when one side of a shoot is exposed to light, in relation to auxins?

A
  • more auxins accumulate on the shaded side
  • cells elongate more quickly on that side, so the shoot bends toward the light
  • allows it to absorb more light for photosynthesis, allowing the plant to grow. (taller shoots have better chances of finding light)
50
Q

are shoots positively or negatively gravitropic?

A

negatively - they grow upwards, away from gravity

51
Q

what happens when a shoot is growing sideways, in relation to auxins?

A
  • more auxins accumulate on the lower side
  • cells on that side grow more quicky, so the shoot bends upwards
52
Q

are roots positively or negatively gravitropic?

A

positively - grow downwards towards gravity

53
Q

what happens if a root is growing sideways, in relation to auxins?

A
  • more auxins accumulate on the lower side
  • inhibits growth there, meaning the top side grows more quickly and the root bends downwards
54
Q

are roots positively or negatively phototropic?

A

negatively - they grow away from light

55
Q

what happens if a root is exposed to light, in relation to auxins?

A
  • more auxins accumulate on the shaded side, meaning that this side grows more slowly, and the root bends downwards into the ground.
56
Q

how can you investigate plant growth in response to light?

A
  • put cress seeds in a petri dish lined with damp filter paper
  • place inside of a black card box, with a hole in one side only.
  • shine a light through the hole, and leave for one week before seeing their response - they should have grown towards the light.
57
Q

how can auxins be used commercially?

A
  • weed killers
  • rooting powders
  • promote growth in tissue culture
58
Q

how can auxins be week killers?

A
  • most weeds are broad leaved and the weed killer can be synthesised so they only affect these
  • increased amount of auxins causes cell to grow too rapidly and die
59
Q

how can auxins be used as rooting powders?

A
  • plants w/ desirable features cloned
  • from cutting from original plant
60
Q

how can auxins be used to promote growth in tissue culture?

A
  • cells taken from plant put into growth medium containing nutrients and auxins are added
61
Q

what can gibberellins be used commercially?

A

in germination for fruit and flower

62
Q

why can gibberellins be used?

A
  • allow seed germination to occur by breaking dormancy
  • allows fruits to grow heavier and larger (increases yields)
  • encourage flowering plants to flower faster
63
Q

what can ethene be used commercially?

A

ripening in the food industry

64
Q

how can ethene be used commercially?

A
  • fruit picked when not ripe
  • firm meaning during transport it gets less bruised / damaged
  • when needed to be sold ethene exposed in warm temperatures
  • controls cell division so stimulates enzymes that result in fruit ripening
65
Q

why is using ethene commercially good?

A

reduces wastage so fruit is suitable to be sold + doesn’t ripen too early

biology gcse (6 decks)

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