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biological sciences > PHOTOSYNTHESIS > Flashcards

PHOTOSYNTHESIS Flashcards

1
Q

what are autotrophs

A

things that produce organic molecules from CO2 – make their own food

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2
Q

what are heterotrophs

A

live off organic compounds produced by other things

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3
Q

what is photosynthesis

A

Process that feeds the biosphere

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4
Q

what are chloroplasts

A
  • sights of photosynthesis
  • capture light energy from the sun – convert it into chemical energy
  • About 500,000 per mm2 of a leaf
  • Found mostly in mesophyll – interior of leaf
  • Each chloroplast has 2 membranes around a dense fluid called stroma
  • Stacks of grana (thylakoids = single) are suspended within the stroma – series of membrane sacs
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5
Q

where are chloroplasts found

A

mesophyll

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6
Q

what are stomata

A

microscopic pores in the leaf where co2 + o2 enter and exit

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7
Q

what is chlorophyll

A

green pigment in chloroplasts (in thylakoid membranes) - absorbes specific wavelength

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8
Q

what is photosynthesis

A

reduction of CO2 using electrons from H2O

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9
Q

what do chloroplasts split water into

A

H + O - incorporating the electrons of H into sugar

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10
Q

2 parts of photosynthesis

A

light reactions / cycles (get some electrons)
Calvin cycle (use the electrons to reduce co2 to sugar)

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11
Q

what happens in light reactions

A
  • water is split
  • reduction of NADP -> NADPH
  • generate ATP from ADP by photophosphorylation
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12
Q

how does energy get transfer through photosystems (light cycle)

A
  • light energy excites chlorophyll in PSII - brings to higher energy shell
  • when the energy is lowered, passes to neighbouring chlorophyll until reaches P680
  • sends electrons in P680 (which are there due to splitting of water) to primary acceptor
  • electrons passed down a chain (makes ATPs)
  • ends up in P700
  • chlorophyll in PSI gets exited - passes electrons in P700 to primary acceptor
  • electrons end up in NADP reductase
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13
Q

major products and byproducts of light cycle

A

major products:
ATP
NADPH
byproducts:
O2

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14
Q

main source of electrons for the light cycle

A

water - pulled from soil by roots of plant

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15
Q

2 kinds of light cycles

A

linear
cyclic

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16
Q

whats the cyclic cycle of the light cycle

A
  • uses only PSI - goes continually from primary acceptor to ETC
  • produces ATP but not NADPH
  • generates surplus ATP - not efficient
  • evolved before linear flow
  • could have a role in protecting cells from light damage
17
Q

whats the Calvin cycle

A
  • uses ATP + NADPH to reduce CO2 to sugar (CH2O)
  • carbon enters the cycle as CO2 and leaves as glyceroldehyde 3 phosphate (G3P - 3C sugar)
  • for net synthesis of 1G3P the cycle must fix 3CO2 molecules - 3C plants
  • 3 stages:
    1. carbon fixation
    2. reduction
    3. regeneration
18
Q

what happen in carbon fixation

A
  • RuBisco - fixes CO2 to 6C molecule - broken into 2X 3C molecules
19
Q

what happen in reduction

A

3C molecules get reduced using the electrons from NADPH

20
Q

what happen in regeneration

A

regenerate all materials so cycle can happen again

21
Q

how does hot air climates relate to rubisco

A

rubisco can combine O2 with catalytic efficiency
- hot climates - lots of O2 inside the cell that can’t get out through stomata (closes to prevent water loss) - photorespiration happens (wasteful process)
- no CO2 can combine with Rubisco if its surrounded by O2

22
Q

what happens in photorespiration

A

rubisco adds an O2 rather than CO2 in Calvin cycle - consumes o2 + organic fuels (RuBP) - destroying 50% carbon mass of planet

23
Q

strategies plants use to make photorespiration not happen

A
  1. change place of carbon fixation - C4 plants
  2. change time of carbon fixation- CAM plants
24
Q

what happens in change place of carbon fixation

A

C4 plants change the location of carbon fixation
- incorporates Co2 INTO 4C compounds in mesophyll cells
- need PEP carboxylase to do this - has higher affinity to CO2 than rubisco
- 4C compounds are transported to bundle-sheath cells - release CO2 then used in Calvin cycle

25
Q

what happens in change time of carbon fixation

A

CAM plants
- open their stomata at night - incorporating CO2 into organic acids
- Stomata close during the day - CO2 is released from organic acids and used in the Calvin cycle

26
Q

what kind of reaction is photosynthesis

A

anabolic

biological sciences (12 decks)

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