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

topic 6 - plant structures and their functions Flashcards

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
how are water and mineral ions transported through the plant?
via transpiration through the stomata
22
what is transpiration?
loss of water from leaves and stems of the plants -> consequence of gas exchange
23
what is translocation?
movement of food substances (eg sucrose) made in leaves up or down phloem for use or storage
24
where does translocation ONLY occur?
phloem
25
how does translocation occur?
from sources (where its made) to the sinks (where its used) -> can depend on season
26
what are stomata?
small openings on a leaf where oxygen, carbon dioxide and water can move/exchange
27
how are stomata adapted in leaves?
able to close to minimise water loss and open to increase evaporation
28
what are guard cells?
cells that open and close the stomata
29
describe guard cells
- kidney shaped - thin outer walls and thick inner walls - light sensitive
30
what do guard cells do when lots of water is available?
cells fill and change shape - open stomata and allow gases to be exchanged and more water to leave the plant
31
where is most stomata found?
bottom of leaf, allowing gases to be exchanged which minimising water loss by evaporation
32
how are chlorophyll adapted in leaves?
green = most efficient colour for absorbing light
33
why are leaves thin?
so CO2 has a short diffusion distance to enter leave and O2 has a short diffusion distance to exit
34
why do leaves have large surface areas?
means leaf can absorb more light at once maximising rate of photosynthesis
35
what environmental factors affect the rate of water uptake?
- temperature increase - increase in humidity - increase in air movement - increase in light intensity
36
how does temperature affect the rate of water uptake?
- 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
how does an increase in humidity affect rate of water uptake?
- if high then the concentration gradient is reduced between concentration of water vapour inside and outside the leaf
38
how does an increase in air movement affect rate of water uptake?
- more air moving from leaf means concentration of water surrounding leaf will be lower - steeper concentration gradient
39
how does an increase in light intensity affect rate of water uptake?
- increased rate of photosynthesis so more stomata open
40
how do you do the rate calculations for transpiration?
using a potometer and measuring how far the bubble moves in capillary tube
41
how does extreme environments affect the cuticle?
many leaves have a waxy cuticle on top = preventing evaporation of water when water is scarce
42
how does extreme environments affect leaves stomata?
can close to prevent evaporation of water or opened when CO2 is needed for photosynthesis
43
what is a phototropism?
response to light
44
what is a gravitropism?
response to gravity
45
what do auxins stimulate?
growth of shoots by cell elongation
46
what do auxins do to growth in the roots and shoots?
shoots = promote growth roots = inhibit growth
47
where are auxins produced?
- tips of shoots and roots - diffuse backwards to stimulate cell elongation
48
are shoots positively or negatively phototropic?
positively - grow towards light
49
what happens when one side of a shoot is exposed to light, in relation to auxins?
- 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
are shoots positively or negatively gravitropic?
negatively - they grow upwards, away from gravity
51
what happens when a shoot is growing sideways, in relation to auxins?
- more auxins accumulate on the lower side - cells on that side grow more quicky, so the shoot bends upwards
52
are roots positively or negatively gravitropic?
positively - grow downwards towards gravity
53
what happens if a root is growing sideways, in relation to auxins?
- more auxins accumulate on the lower side - inhibits growth there, meaning the top side grows more quickly and the root bends downwards
54
are roots positively or negatively phototropic?
negatively - they grow away from light
55
what happens if a root is exposed to light, in relation to auxins?
- more auxins accumulate on the shaded side, meaning that this side grows more slowly, and the root bends downwards into the ground.
56
how can you investigate plant growth in response to light?
- 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
how can auxins be used commercially?
- weed killers - rooting powders - promote growth in tissue culture
58
how can auxins be week killers?
- 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
how can auxins be used as rooting powders?
- plants w/ desirable features cloned - from cutting from original plant
60
how can auxins be used to promote growth in tissue culture?
- cells taken from plant put into growth medium containing nutrients and auxins are added
61
what can gibberellins be used commercially?
in germination for fruit and flower
62
why can gibberellins be used?
- allow seed germination to occur by breaking dormancy - allows fruits to grow heavier and larger (increases yields) - encourage flowering plants to flower faster
63
what can ethene be used commercially?
ripening in the food industry
64
how can ethene be used commercially?
- 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
why is using ethene commercially good?
reduces wastage so fruit is suitable to be sold + doesn't ripen too early

biology gcse (6 decks)

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