module 5 - 17.4 factors affecting photosynthesis Flashcards

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1
Q

what are the limiting factors affecting the rate of photosynthesis?

A
  • light intensity
  • light quality (what wavelengths)
  • carbon dioxide concentration
  • temperature
  • stomatal status - open or closed
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2
Q

how is light intensity a limiting factor affecting the rate of photosynthesis?

A

as light increases, ATP and reduced NADP are produced at a higher rate

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3
Q

how is light quality a limiting factor affecting the rate of photosynthesis?

A

light with a higher proportion of energy concentrated in these wavelengths will produce a higher rate of photosynthesis.

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4
Q

how is carbon dioxide concentration a limiting factor affecting the rate of photosynthesis?

A

increasing the carbon dioxide concentration increases the rate of carbon fixation in the calvin cycle and increases rate of ATP

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5
Q

how is temperature a limiting factor affecting the rate of photosynthesis?

A
  • affects rate of enzyme controlled reactions
  • as temp increases, rate of anzyme activity increases until proteins denature
  • increase in temp increases rate of enzyme controlled reactions in photosynthesis
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6
Q

how is stomatal status a limiting factor affecting the rate of photosynthesis?

A
  • stomata close on leaves to avoid water loss through transpiration during dry weather
  • closing stomata stops diffusion of carbon dioxide in plants, reducing rate of light independent reactions and stops photosynthesis
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7
Q

what will happen if light intensity is reduced from high to low? (effect on calvin cycle)

A
  1. rate of reaction of light dependent stage reduces
  2. concentration of ATP and reduced NADP will reduce
  3. conc. of GP increases as ATP and reduced NADP are needed to convert GP to TP so conc. of these molecules is reduces
  4. conc. of TP reduces as ATP and reduced NADP are needed to convert GP to TP and conc. od ATP and reduced NADP reduces
  5. conc. of RuBP reduces because of lower conc. of TP it’s made from
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8
Q

what will happen if the concentration of CO2 is reduced from high to low? (effect on calvin cycle)

A
  1. concentration of GP is reduced as there is less CO2 to be fixed
  2. conc. of TP is reduced as there is less GP that its made from
  3. conc. of RuBP increases due to lack of CO2 to be fixed
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9
Q

what will happen if temperature reduces? (effect on calvin cycle)

A
  1. reducing kinetic energy of all enzymes and substrates of Calvin Cyle
  2. reducing number of successful collisions between enzymes and substrates
  3. reducing overall rate of reaction of Calvin Cycle
  4. reducing conc. of GP, TP & RuBP
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10
Q

what will happen if temperature increases to high temperatures? (effect on calvin cycle)

A
  1. enzymes in Calvin Cyle will be irreversibly denatured
  2. reducing concentrations of GP, TP & RuBP
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11
Q

what does “fixed” mean?

A

adding hydrogen to inorganic carbon from reduced NAD

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12
Q

what is C4 photosynthesis?

A
  • alternative to normal C3 photosynthesis
  • called C4 as CO2 molecules are fixed to make a 4-carbon molecule, not by RUBISCO
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13
Q

what is carbon dioxide fixed by in C4 photosynthesis?

A
  • enzyme called PEP CARBOXYLASE and produces 4-carbon OXALOACETATE
  • PEP CARBOXYLASE has no affinity for oxygen
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14
Q

where is oxaloacetate transported in C4 photosynthesis?

A
  • transported into bundle sheath cells around the vascular bundles
  • it is then decarboxylated to produce carbon dioxide
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15
Q

what does RUBISCO convert carbon dioxide and RuBP into, after the oxaloacetate is decarboxylated? (C4 photosynthesis)

A
  • converts them into the 6-carbon intermediate and 2 GP molecules
  • this means RUBISCO is shielded form oxygen produced by photolysis in the chloroplast and also has high conc. of CO2
  • the 2 GP is transported back to normal photosynthetic cells
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16
Q

what are C4 plants adapted to?

A

adapted to high light levels and low water levels

17
Q

what does CAM stand for?

A

crassulacean acid metabolism

18
Q

what is CAM photosynthesis?

A

alternative to normal C3 photosynthesis

19
Q

what do CAM plants do?

A
  • close their stomata all day to reduce water loss by transpiration and only open them during the cooler night
  • the CO2 they absorb at night is converted to malic acid
  • malic acid builds up at night as a store of CO2
20
Q

what is malic acid?

A

a 4-carbon molecule

21
Q

what happens to the malic acid during the day?

A
  • when stomata close, the malic acid is transported into chloorplasts
  • malic acid is converted back to CO2
22
Q

what does RUBISCO use carbon dioxide and RuBP to make?

A

uses CO2 and RuBP to make the 6-carbon intermediate, rest of Calvin Cycle turns as normal

23
Q

how are CAM plants adapted?

A

adapted to high light levels and arid conditions when stomata only open at night e.g. cacti

24
Q

which 2 reactions occur during phosphorylation?

A
  • ATP is synthesised
  • NADP is reduced
25
Q

which reaction is catalysed by the enzyme RUBISCO?

A

carboxylation of ribulose bisphosphate (RuBP)

26
Q

which pair of areas within a chloroplast will show the steepest pH gradient between them?

A

stroma and the thylakoid space within thylakoid membrane