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nutrition (plants) Flashcards

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1
Q

photosynthesis definition + features

A

the process by which plants manufacture carbohydrates from raw materials using the energy from light
it is the opposite of respiration and is endothermic meaning that it requires the absorption of heat

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2
Q

photosynthesis process

A

energy from sunlight is absorbed by chlorophyll (green pigment found in chloroplasts), green plants use this energy to make carbohydrates from raw materials (carbon dioxide and water), at the same time oxygen is made and released as a waste product

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3
Q

features of plants

A

autotrophs - they can make complex organic molecules (eg glucose) from simple inorganic molecules (carbon dioxide and water) (plants are specifically photoautotrophs)
producers - they can make their own food and so are the first organisms at the start of all food chains

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4
Q

word equation

A

carbon dioxide + water —> glucose + oxygen

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5
Q

symbol equation

A

6CO2 + 6H2O —> C6H12O6 + 6O2

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6
Q

how does carbon dioxide come into the leaf

A

diffuses into the leaf through the stomata

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7
Q

how does water come into the leaf

A

it is taken up through the roots and transported through the xylem to the leaves

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8
Q

what is glucose used for in the leaf

A

used to carry out processes
- source of energy in respiration
- produces starch for storage
- synthesises lipids (converted into fats or oils) for an energy source in seeds
- forms cellulose to make cell walls
- produces amino acids (used to make proteins) when combined with nitrogen and other mineral ions absorbed by roots

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9
Q

how does oxygen leave the leaf

A

diffuses out of the leaf through the stomata or used in respiration

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10
Q

factors affecting the rate of photosynthesis

A

temperature, light intensity and carbon dioxide concentration (limiting factors) and the amount of chloroplasts

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11
Q

limiting factor

A

something present in the environment in such short supply that it restricts life processes

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12
Q

other factor that may impact the rate of photosynthesis

A

water, but there is hardly a situation where there is not enough water for photosynthesis to occur

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13
Q

how does temperature affect photosynthesis

A
  • affects how much kinetic energy the particles have, therefore the speed that CO2 and H2O move through a plant
  • lower temperature = less kinetic energy = fewer successful collisions occur over time between the reactants and enzymes
  • higher temperatures increase the likelihood of successful collisions between reactants and enzymes, this results in the formation of products
  • really high temperatures can cause the enzymes controlling photosynthesis to be denatured (heat causes bonds to break, causing the active site to change shape so that it is no longer complimentary to the substrate) reducing the overall rate of photosynthesis
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14
Q

how does light intensity affect photosynthesis?

A

intensity of light affects the amount of energy that a plant has to carry out photosynthesis
more light = faster rate of photosynthesis
this trend will continue until one other factor required for photosynthesis prevents the rate of photosynthesis from increasing further as it is now in short supply

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15
Q

how does CO2 concentration affect photosynthesis?

A

one of the raw materials required for photosynthesis
more CO2 present = faster the reaction can occur
trend continues until another factor required for photosynthesis prevents the rate from increasing further as it is now in short supply

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16
Q

How does chlorophyll affect the rate of photosynthesis? and why?

A

more chloroplasts = more chlorophyll = faster rate of photosynthesis as more light energy can be absorbed at a time

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17
Q

what can the amount of chlorophyll be affected by

A

diseases eg tobacco mosaic virus
lack of nutrients eg magnesium
loss of leaves = fewer chloroplasts

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18
Q

leaf structures

A

waxy cuticle, upper epidermis, palisade mesophyll, spongy mesophyll, lower epidermis, guard cell, stomata, vascular bundle, xylem, phloem

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19
Q

waxy cuticle definition

A

protective layer on top of the leaf

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20
Q

upper epidermis definition

A

thin and transparent layer of cells above the palisade cells

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21
Q

palisade mesophyll

A

column shaped cells tightly packed with chloroplasts

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22
Q

spongy mesophyll

A

cells packed loosely together below the palisade cells

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23
Q

lower epidermis

A

contains guard cells and stomata

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24
Q

guard cell

A

allows gas exchange and controls water loss within the leaf. they control when the stomata open and close

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25
stomata
site of gas exchange, open during the day, closed at night. evaporation of water takes place from here. in most plants they are found in greater concentration on the underside of the leaf to reduce water loss
26
vascular bundle
contains xylem and phloem to transport substances to and from the leaf
27
xylem
transports water into the leaf for mesophyll cells to use in photosynthesis and for transpiration (loss of water vapour) from stomata
28
phloem
transports sucrose and amino acids around the plant
29
leaf adaptations for photosynthesis
surface area, thin, chlorophyll, network of veins, stomata, epidermis, waxy cuticle, palisade mesophyll, spongy mesophyll, vascular bundles
30
surface area
large surface area increases surface area for diffusion of CO2 and the absorption of light for photosynthesis
31
thin
short diffusion distance for CO2 to diffuse into palisade mesophyll cells
32
chlorophyll
absorbs light energy so photosynthesis can take place
33
network of veins
allows transport of water to the cells of the leaf and carbohydrates from the leaf (after being produced by photosynthesis)
34
How stomata assist in photosynthesis
allows CO2 to diffuse into the leave and O2 to diffuse out of the leaf
35
epidermis adaptation
thin and transparent allowing more light to reach the palisade cells quickly
36
waxy cuticle adaptations
thin and made of wax to protect the leaf (from water loss and bacteria) without blocking sunlight. this allows light energy to reach the palisade cells
37
palisade mesophyll adaptations
located at the top of the leaf, maximising the absorption of light as it will hit the chloroplasts in the cells directly. cells have large vacuoles to push the chloroplasts out to the sides for maximum light absorption
38
spongy mesophyll adaptations
covered by thin layer of water for gases to dissolve in as they move in and out of the cells, the air spaces increase the surface area, allowing CO2 to diffuse through the leaf quicker
39
vascular bundle adaptations
thick cell walls of the tissue in the bundles help support the stem and the leaf
40
what does photosynthesis provide a source of?
carbohydrates, but plants contain and require many other types of biological molecule (protein, lipids, nucleic acid (DNA))
41
where do plants get these substances from?
they make them themselves as they cannot eat
42
mineral ions required by plants and why
nitrogen + magnesium without a source of them, plants cannot photosynthesise or grow properly
43
how do plants obtain mineral ions
in the form of mineral ions actively absorbed from the soil by root hair cells
44
what is a mineral?
term describing any naturally occurring inorganic substance
45
nitrate ion function in plants + deficiency
source of nitrogen combined with glucose to make amino acids (that build proteins) and enable growth deficiency causes stunted growth and the yellowing of leaves
46
magnesium ion function in plants + deficiency
needed to make chlorophyll (that absorbs light energy for photosynthesis) deficiency causes yellowing between the veins of the leaves (chlorosis)
47
plants used in evolution of oxygen practical
elodea, cabomba - types of pondweed (water plants)
48
how can the oxygen be seen (evolution of oxygen practical)
as the plant is in water, O2 released can be seen as bubbles leaving the cut end of the pondweed
49
method (evolution of oxygen practical)
submerge a bundle of shoots of the water plant in a beaker of water underneath an upturned funnel fill a boiling tube with water and place it over the end of the funnel as oxygen is produced, bubbles of gas will collect in the boiling tube and displace the water
50
how to prove the results (evolution of oxygen practical)
show gas collected is oxygen by relighting a glowing splint
51
what substance's presence cannot be tested for on a leaf?
plants synthesise glucose during photosynthesis leaves cannot be tested for presence of glucose as it is quickly used up, converted into other substances and transported or stored as starch
52
what does testing for starch show
testing for starch is a reliable indicator for which parts of the leaf are photosynthesising
53
where is starch stored on plants
in the chloroplasts where photosynthesis occurs
54
method (light and photosynthesis practical)
de starch the plant (place in dark cupboard for 24 hours) this ensures that any starch already present in the leaves will be used up and will not affect the results of the experiment partially cover a leaf of the plant with aluminium foil and place the plant in sunlight for a day remove the covered leaf and test for starch
55
how to prepare a leaf for a test for iodine (light and photosynthesis practical)
drop leaf in boiling water (kills tissue and breaks down cell walls, stopping chemical reactions from taking place) transfer leaf into a boiling tube filled with ethanol for 5 -10 minutes (removes chlorophyll from the leaf so colour changes from iodine can be seen clearer) rinse leaf in cold water (softens leaf tissue after being in ethanol) spread leaf on a white tile and cover it with iodine solution
56
results of iodine colour changes (light and photosynthesis practical)
green leaf - iodine turns blue-black as photosynthesis occurs in all areas of the leaf part covered with aluminium foil - iodine remains orange-brown, did not receive sunlight, could not photosynthesise and did not produce glucose that was turned into starch areas exposed to sunlight turn blue-black
57
what does this prove (light and photosynthesis practical)
that light is necessary for photosynthesis and the production of starch
58
safety (light and photosynthesis practical)
ethanol is extremely flammable heat it in an electric water bath instead of a Bunsen burner with an open flame
59
what test can be used in the practical investigating CO2 and photosynthesis
the iodine test for starch can investigate the requirement of CO2 in photosynthesis
60
method (investigating CO2 and photosynthesis)
de starch plant by placing it in a dark cupboard for 24 hours (any starch already present in leaves will be used up and not affect the results of the experiment) enclose 1 leaf with a conical flask containing potassium hydroxide (absorbs CO2 from surrounding air) enclose another leaf in a conical flask containing no potassium hydroxide place plant in light for several hours and test both leaves for starch using iodine solution (drop leaf in boiling water, transfer leaf into hot ethanol in a boiling tube for 5-10 minutes, rinse in cold water, spread leaf out on a white tile and cover it with iodine solution)
61
results (investigating CO2 and photosynthesis)
conical flask with potassium hydroxide leaf turns orange brown (could not photosynthesise due to lack of carbon dioxide) conical flask without potassium hydroxide turns blue black (had all necessary requirements for photosynthesis to occur)
62
test used + why (investigating chlorophyll and photosynthesis)
test for starch used as starch stored in chloroplasts where photosynthesis occurs so testing a leaf for starch is a reliable indicator so is a reliable indicator of which parts of the leaf are phtotsynthesising method also tests whether chlorophyll is needed for photosynthesis by using a variegated (part green + white) leaf
63
method (investigating chlorophyll and photosynthesis)
drop leaf into boiling water (kills tissue, breaks down cell walls) transfer leaf into hot ethanol in a boiling tube for 5-10 minutes (removes chlorophyll so colour changes from iodine can be seen more clearly) rinse leaf in cold water (softens leaf tissue after being in ethanol) spread leaf out on a white tile and cover it with iodine
64
safety (investigating chlorophyll and photosynthesis)
ethanol is extremely flammable heat ethanol in electric water bath instead of Bunsen burner with open flame
65
results and analysis (investigating chlorophyll and photosynthesis)
white areas of the leaf do not contain any chlorophyll only areas that contain chlorophyll stain blue black areas that had no chlorophyll cause the iodine to remain orange brown as no photosynthesis is occurring here and so no starch is stored

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