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photosynthesis Flashcards

1
Q

photosynthesis equation

A

6CO2 + 6H20 = C6H12O6 + 6O2

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2
Q

adaptions of a leaf for photosynthesis

A
  • large SA
  • thin
  • stomatal pores
  • air spaces in spongy mesophyll
  • spaces between palisade cells
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3
Q

large SA significance for photosynthesis

A

capture as much light as possible

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4
Q

thin leaf significance for photosynthesis

A

light penetrates through the leaf

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5
Q

stomatal pores significance for photosynthesis

A

allows CO2 to diffuse into the leaf

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6
Q

spaces between palisade cells and air spaces in spongy mesophyll significance for photosynthesis

A

allows CO2 to diffuse into to the photosynthesising cells

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7
Q

leaf cell adaptions for photosynthesis

A
  • transparent cuticle and epidermis
  • thin cellulose cell walls
  • large vacuole in palisade cells
  • cylindrical palisade cells
  • palisade cells elongated at right angles to leaf surface
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8
Q

transparent cuticle and epidermis, and thin cellulose cell walls significance for photosynthesis

A

light penetrates through to mesophyll

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9
Q

large vacuole in palisade cells significance for photosynthesis

A

chloroplasts form a single layer so they don’t shade each other

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10
Q

cylindrical and elongated at right angles palisade cells significance for photosynthesis

A
  • leaves accommodate a large number of palisade cells
  • light only passes through 2 epidermal cell walls and 1 palisade cell wall to reach chloroplasts
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11
Q

chloroplast adaptions for photosynthesis

A
  • large SA
  • can move and rotate within palisade cells
  • pigments in thylakoid in single layer at surface of thylakoid membrane
  • more chloroplasts in palisade than spongy mesophyll cells
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12
Q

chloroplast large SA significance for photosynthesis

A

maximum absorption of light

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13
Q

chloroplasts can move and rotate within palisade cells significance for photosynthesis

A
  • move to top of cell on dull days for max light absorption
  • high light intensity moves to bottom to protect pigments from bleaching
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14
Q

pigments in thylakoid in single layer at surface of thylakoid membrane significance for photosynthesis

A

thylakoids maximise light absorption

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15
Q

more chloroplasts in palisade than spongy mesophyll cells significance for photosynthesis

A

palisade cells are at top of leaf so more exposed so chloroplasts can maximise light absorption

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16
Q

pigments in thylakoids are in a single layer at surface of thylakoid membrane significance for photosynthesis

A

pigments maximise light absorption

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17
Q

photophosphorylation

A

an endergonic reaction bonding a phosphate ion to a molecule of ADP, using energy from light, making ATP
- non-cyclic vs cyclic

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18
Q

thylakoid lamellae

A

folded inner membrane of chloroplasts

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19
Q

stroma

A

fluid filled chloroplast interior
bathes thylakoids and grana
location of light independent stage
contains enzymes for photosynthesis

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20
Q

grana

A

stacks of thylakoids
location of photosynthetic pigments
location of light dependent stage

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21
Q

why are starch grains white?

A

stain binds to lipids

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22
Q

where are chloroplasts found in a leaf?

A
  • leaves and stems
    areas exposed to light
  • in palisade and spongy mesophyll
  • in guard cells
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23
Q

what is a transducer?

A

changes energy from one form to another.
biological transducers waste little energy

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24
Q

how are chloroplasts transducers?

A

they turn energy in photons of light into chemical energy, made available through ATP and incorporated into molecules

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25
Q

what is a photosynthetic pigment?

A

a molecule that absorbs specific wavelengths of light
traps light energy
different pigments = trap different wavelengths

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26
Q

types of photosynthetic pigments

A
  • chlorophyll a = blue/green
  • chlorophyll b = yellow/green
  • b-carotene = orange
  • xanthophyll = yellow
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27
Q

chlorophyll definitation

A

protein containing magnesium, bound to thylakoid membrane

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28
Q

absorption spectrum

A

a graph showing how much light is absorbed at different wavelengths
( relative absorption)

29
Q

patterns of absorption spectrum

A
  • chlorophyll a+b absorb light energy in red/blue-violet regions, and reflect green
  • carotenoids absorb light energy in blue/green region, so appear yellow/orange
30
Q

action spectrum

A

graphs showing rate of photosynthesis at different wavelengths
- measured by mass of carb synthesised by plant at various wavelengths

31
Q

where are photosystems found

A

in the plane of the thylakoid membrane

32
Q

what is a photosystem made of?

A
  • antenna complex
  • reaction centre
    they are a collection of accessory pigments
33
Q

antenna complex

A
  • contains photosynthetic pigments, anchored into phospholipids of thylakoid membrane
    held together by clusters of protein molecules
  • consists of one cluster
  • pigments combos = various wavelengths absorbed
  • transfer energy to chlorophyll a in reaction centre
34
Q

reaction centre of photosystems

A
  • within antenna complex
  • 2 molecules of primary pigments (chlorophyll a). absorbs light, excitation emits 1 electron each
35
Q

PS1

A

arranged around chlorophyll a molecule
absorption peak = 700nm

36
Q

PS2

A

arranged around chlorophyll a molecule
absorption peak = 680nm

37
Q

accessory pigments

A
  • chlorophyll b and carotenoids
    light absorbing molecules, pass energy through to reaction centre to reach chlorophyll a
    excited chlorophyll a electrons = energy level raised
38
Q

chlorophyll a

A
  • primary pigment
    passes energy to subsequent reactions of photosynthesis
39
Q

what does the light dependent stage produce?

A
  • ATP, to synthesis molecules (glucose)
  • reduced NADP, to reduce synthesising molecules
  • oxygen, by-product, diffuses out leaf
40
Q

cyclic photophosphorylation

A
  • PS1
  • electrons cycle
  • in all photosynthetic organisms
41
Q

non-cyclic photophosphorylation

A
  • PS1 + PS2
  • linear electron pathway
  • in plants, algae, cyanobacteria
42
Q

cyclic photophosphorylation stages

A
  • PS1 absorb photons, excites chlorophyll a electrons (in reaction centre)
  • electrons emitted and picked up by electron acceptor
  • pass down electron carriers to PS1
  • energy released phosphorylates ADP to ATP
  • electrons path: PS1 to electron acceptor to PS1
  • electron recycled into chlorophyll a
43
Q

non-cyclic photophosphorylation stages

A
  • PS2 absorbs light energy, excites pair of electrons in chlorophyll a and leave it
  • electron carrier takes up pair
  • electrons need to be replaced. photolysis of water provides electrons
  • electrons pass down transport chain, each stage loses energy
  • lost energy combines Pi with ADP = ATP
  • light energy absorbed by PS1 excites electrons
  • electrons and 2H transferred to NADP = reduced NADP
    enters independent reaction
44
Q

photolysis of water

A
  • splitting of water molecules by light in thylakoid spaces
  • indirectly produces 2H, 2 electrons, 1/2 oxygen
  • electrons replace those lost from PS2
  • protons and electrons (from PS1) reduce NADP
  • oxygen diffuses out stomata (waste product)
45
Q

Rf value calculation

A

distance travelled by pigment
divided by
distance travelled by solvent front

46
Q

what is chemiosmosis?

A

the process of moving ions (protons) to the other side of a biological membrane
- through ATP synthetase, into stroma
- produces electrochemical gradient
- once in stroma protons can reduce NADP

47
Q

3 factors that maintain proton gradient between thylakoid space and stroma

A
  • proton pump (protons into thylakoid space)
  • photolysis of water
  • removal of protons from stroma, reduces NADP
48
Q

carboxylation of light independent stage steps

A
  • CO2 enters chloroplasts
  • CO2 combines with RuBP (5C) catalysed by rubisco
  • unstable 6C compound formed
  • 6C splits into 2 molecules of a 3C compound, glycerate-3-phosphate (GP)
49
Q

reduction of light independent stage steps

A
  • GP reduced to TP (3C). reduced NADP provides H ions, ATP provides energy
  • NADP reformed and recycled
  • TP converted to useful compounds (glucose), then to starch
50
Q

regeneration of light independent stage steps

A
  • 5/6 TP molecules produced regenerate RuBP
  • rest of ATP provides energy
51
Q

products of calvin cycle

A
  • carbohydrate: hexose sugar, glucose (fructose bisphosphate)
  • lipids: produced from TP
  • proteins: amino acids produced using nitrogen from nitrates
52
Q

hexose sugars

A
  • monosaccharide, 6C
  • made by joining 2TP
  • 1 hexose sugar = 6 calvin cycle turns
53
Q

what is a limiting factor?

A
  • factor that limits the rate of a physical process by being in short supply
54
Q

how does CO2 limit photosynthesis?

A
  • when in short supply it limits photosynthesis
  • CO2 increase = photosynthesis increases
  • eventually plateaus
55
Q

how does light intensity limit photosynthesis ?

A
  • plant in darkness = light dependent reaction can’t occur
  • light intensity increases = efficiency of light dependent reaction increases
  • eventually reaches max rate
  • if too high = photosynthetic pigments damaged = no photosynthesis
56
Q

how does temperature limit photosynthesis?

A
  • involves enzymes, so increase in temp = increased KE = increase successful collisions = increased rate of reaction
  • temp above optimum = enzymes denature = decreases rate
57
Q

how does water limit photosynthesis?

A
  • when water is scarce, plant cells plasmolyse = stomata close = wilting
58
Q

sun plants

A

most efficient at high light intensities

59
Q

shade plants

A

most efficient at low light intensities

60
Q

light compensation rate

A

light intensity at which a plant has no net gas exchange.
volumes of gases used and produced in photosynthesis and respiration are equal
- low light intensity = decreased rate of photosynthesis = decreased CO2 uptake. so respiration provides all the CO2 needed. and all the O2 needed for respiration is provided by photosynthesis

61
Q

roles of inorganic nutrients in plants

A
  • structural
  • synthesis of compounds for growth
  • form molecule parts, e.g. magnesium in chlorophyll
62
Q

function of nitrogen in plants

A
  • synthesis of nucleic acids, proteins and chlorophylls
  • become amino groups of amino acids
63
Q

symptoms of nitrogen deficincy

A
  • reduced growth of entire plant
  • yellow leaves = chlorosis
64
Q

function of magnesium in plants

A
  • chlorophyll production
65
Q

symptoms of magnesium deficiency

A
  • yellow leaves = chlorosis
    begins in older veins as Mg is prioritised to newer leaves
66
Q

explain the advantage of plants having more than one pigment in their leaves

A
  • light can be absorbed over a greater range of wavelengths
  • more light absorbed = more products from light dependent stage
  • greater rate of photosynthesis
67
Q
A
68
Q
A

Biology eduquas (11 decks)

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