Photosynthesis Flashcards

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1
Q

Where do the LDR and LIDR occur in plants?

A
  • LDR = thylakoid membranes.
  • LIDR = stroma.
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2
Q

Explain the role of light in phosphoionisation.

A

Chlorophyll molecules absorb energy from photons of light.
This ‘excites’ 2 electrons (raises them to a higher energy level), causing them to be released from the chlorophyll.

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3
Q

Name the 2 main stages involved in ATP production in the LDR.

A
  1. electron transfer chain
  2. chemiosmosis
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4
Q

What happens in the electron transfer chain?

A

Electrons released from the chlorophyll move down a series of carrier proteins embedded in the thylakoid membrane & undergo a series of redox reactions, which releases energy.

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5
Q

How is a proton concentration gradient established during chemiosmosis?

A

Some energy released from the ETC is coupled to the active transport of H+ ions (protons) from the stroma into the thylakoid space.

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6
Q

How does chemiosmosis produce ATP in the LDR.

A

H+ ions (protons) move down their concentration gradient from the thylakoid space into the stroma via the channel protein ATP synthase.
ATP synthase catalyses ADP + Pi –> ATP.

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7
Q

Explain the role of light in photolysis.

A

Light energy splits molecules of water.
2H2O –> 4H+ + 4e- + O2

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8
Q

What happens to the products of the photolysis of water?

A
  • H+ ions: move out of thylakoid space via ATP synthase & are used to reduce the coenzyme NADP.
  • e-: replace electrons lost from chlorophyll.
  • O2: used for respiration or diffuses out of leaf as waste gas.
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9
Q

How and where is reduced NADP produced in the LDR?

A
  • NADP + 2H+ + 2e- –> NADPH.
  • Catalysed by dehydrogenase enzymes.
  • Stroma of chloroplasts.
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10
Q

Where do the H+ ions and electrons used to reduce NADP come from?

A
  • H+ ions: photolysis of water.
  • Electrons: NADP acts as the final electron acceptor of the electron transfer chain.
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11
Q

Name the 3 main stages in the Calvin cycle.

A
  1. Carbon fixation.
  2. Reduction.
  3. Regeneration.
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12
Q

What happens during carbon fixation?

A
  • Reaction between CO2 & ribulose bisphosphate (RuBP) catalysed by rubisco.
  • Forms unstable 6C intermediate that breaks down into 2x glycerate 3-phosphate (GP).
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13
Q

What happens during reduction (in the Calvin cycle)?

A
  • 2 x GP are reduced into 2 x triose phosphate (TP).
  • Requires 2 x reduced NADP & 2 x ATP.
  • Forms 2 x NADP & 2 x ADP.
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14
Q

How does the LIDR result in the production of useful organic substances?

A

1C leaves the cycle (i.e., some of the TP is converted into useful organic molecules).

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15
Q

What happens during regeneration (in the Calvin cycle?)

A
  • After 1C leaves the cycle, the 5C compound RuP forms.
  • RuBP is regenerated from RuP using 1 ATP.
  • Forms 1 ADP.
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