Photosynthesis Flashcards

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1
Q

Name the 4 structural regions of the chloroplast

A
  • Envelope (pair of outer limiting membranes)
  • Stroma (unstructured background matrix)
  • Thylakoids (highly structured internal system of membranes)
  • Lumen (intra-thylakoid space)
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2
Q

Thylakoids

A
  • Can be stacked (appressed) or unstacked (non-appressed)
  • Provides network of interconnections between grana
  • Contains chlorophyll and carotenoid pigments
  • The site of light dependent energy conserving reaction
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3
Q

Name the 4 major protein complexes in the thylakoid

A
  • Photosystem II
  • Cytochrome b6f complex
  • Photosystem I
  • ATP synthase
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4
Q

What is the redox reaction?

A

Energy transfer from one molecule to another (reduction and oxidation)

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5
Q

What is OILRIG?

A

Oxidation is loss of electrons (oil) and reduction is gain of electrons (rig)

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6
Q

Photosystem II (PSII)

A
  • Multi-subunit protein complex
  • Contains 300 chlorophyll molecules
  • Light harvesting complex (LHC)
  • Reaction centre core
  • D1 and D2 proteins
  • Oxygen evolving complex
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7
Q

Light transfers

A

Energy is transferred to pigments which absorb light until it reaches the reaction centre in PSII which transfers an electron to an electron acceptor

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8
Q

What reaction is carried out by the oxygen evolving complex in PSII?

A

2 H20 = O2 + 4H+ + 4e-

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9
Q

PSI reaction centre

A

Excites electrons and sends them to electron acceptor and stored in NADPH

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10
Q

What is oxidative phosphorylation?

A

High energy molecules in PSI cause proton molecules to flow down a gradient to produce ATP

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11
Q

Proton gradient across thylakoid membrane

A
  • 3 pH units
  • Lumen is more acidic than stroma
  • NADPH is produced and proton gradient is used to produce ATP
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12
Q

Light dependent photosynthesis

A

Produces ATP and NADP

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13
Q

Dark reactions

A

ATP and NADPH make sugars from CO2

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14
Q

What is carbon fixing?

A
  • Requires high energy molecules
  • Fixed into carbohydrates via Calvin-Benson cycle
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15
Q

What are the 3 stages of the Calvin cycle?

A
  • Carbon fixation
  • Reduction of 3-PGA
  • Regeneration of RuBP
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16
Q

What is the use of carboxylase in the Calvin cycle?

A

Produces 2 molecules of PGA

17
Q

What is the use of oxygenase in the Calvin cycle?

A

Produces 1 molecule of PGA and PG

18
Q

What is photorespiration?

A
  • Uses oxygen instead of CO2
  • Competes for reaction at the same site as enzyme
  • Produces phosphoglycerate instead of carbon fixing
19
Q

Important steps of Calvin cycle

A
  • RuBP joins with CO2 to give 2 molecules of 3-PGA
  • Enzyme that carries out first step is called RUBISCO
  • Energy in the form of ATP and NADPH
  • G3P can be used to make hexose sugars
  • Most G3P is recycled back to RuBP
  • Reaction occur in the stroma