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BIOL 241 > Topic 6: Phototrophic Metabolism > Flashcards

Topic 6: Phototrophic Metabolism Flashcards

1
Q

What happens in the formation of glucose and O2 from CO2 and H2O?

A
  • CO2 is reduced to form glucose
  • H2O is oxidized to form O2
  • Polar covalent bonds in reactants are broken
  • Non-polar covalent bonds in the products are formed
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2
Q

What are the membranes in the Chloroplast?

A
  • Outer membrane
  • Inner membrane
  • Thylakoid
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3
Q

What are the two important spaces in the Chloroplast?

A
  • Stroma
  • Thylakoid lumen
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4
Q

What does the photosynthetic process consist of?

A
  • Light reaction (transforming solar energy into chemical energy)
  • Dark reaction (use chemical energy to fix CO2 into carbohydrates)
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5
Q

What are the similarities between Photosynthesis and Cellular Respiration? (3 things)

A
  • ATP Synthase
  • Both use proton gradient
  • Electron taxis
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6
Q

What are the differences between Photosynthesis and Cellular Respiration? (1 thing)

A
  • Not happening spontaneously in photosynthesis, needs energy from the sun
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7
Q

Relationship between associated with light and wavelength

A

Inversely proportional

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8
Q

When a photon strikes an object, it can be…

A
  1. Reflected (bounced back)
  2. Transmitted (passed right through the object)
  3. Absorbed (absorbed by electrons which gain energy from the photon)
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9
Q

Pigments absorb photons of specific wavelengths under what conditions?

A

The wavelength must exactly match the energy needed to raise an electron to a higher energy level

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10
Q

When a photon is absorbed by an electron what happens?

A

It becomes excited and moves from a low-energy level to a high-energy level

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11
Q

What are embedded into the thylakoid membrane?

A

Photosynthetic pigments

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12
Q

What are Chlorophylls?

A

The main pigment in most photoautotrophs

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13
Q

Carotenoids act as…

A

Accessory pigments

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14
Q

What are photosystems?

A

Complexes with proteins where pigment molecules are organized (light-harvesting complexes)

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15
Q

Where are hundreds of antenna pigments grouped?

A

Grouped around a reaction centre

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16
Q

What happens when antenna pigments are excited?

A

Channel energy to the reaction centre (inductive resonance)
- “players passing (antenna) a basketball to the net (reaction centre) “

17
Q

What is a reaction centre?

A

A collection of proteins that interact with pigments

18
Q

What is Inductive Resonance?

A

The transfer of energy from one electron to another

19
Q

How do Reaction centres reduce a Primary Electron Acceptor?

A
  • Light is absorbed by an antenna pigment
  • Energy is transferred by inductive resonance to a reaction centre
  • The reaction centre donates an electron to a primary electron acceptor (PEA)
20
Q

What does photosystem II do?

A
  1. Absorb energy from photons
  2. P680 (in its reduced form), the electron gets excited
  3. P680+ donates excited electron to PEA
  4. P680+ (in its oxidized form), accepts an electron donated by water (which is oxidized)
  5. Returns to P680 (in its reduced form)
21
Q

What do a low [H+] and a high [H+] mean for pH?

A

Low [H+] = higher pH
High [H+] = lower pH

22
Q

How does Photosystem II produce PMF?

A
  1. P680 reduces its PEA, which passes the electron to PQ (plastoquinone)
  2. PQ is a hydrophobic electron taxi, that grabs a proton from the stroma when reduced
  3. PQ reduces cytochrome complex and releases a proton into the lumen
  4. Cytochrome reduces plastocyanin that passes electron to P700+
23
Q

What does Photosystem I do?

A
  1. P700 absorbs energy from the sun
  2. P700 (reduced form), the electron gets excited
  3. P700+ donates excited electrons to the PEA
  4. P700+ (oxidized form), gains an electron from plastocyanin which is oxidized)
  5. Returns to P700 (reduced form)
24
Q

How does Photosystem I produce NADPH

A
  1. P700 reduced PEA, which passes electrons to ferredoxin
  2. Ferredoxin (an electron taxi) in the stroma reduces NADP+ reductase
  3. NADP+ reductase reduces NADP+ to NADPH in the stroma
    *P700, replaces its electrons by accepting electrons from plastocyanin
25
Q

How is PMF created by the photosystems?

A
  1. Protons in the stroma are used to reduce NADP+ to NADPH
  2. Oxidation of H2O in the lumen releases protons
  3. PQ moves protons from the stroma to the lumen
26
Q

What is Photophosphorylation?

A

Using solar energy to generate PMF to power ATP Synthase (ATP is generated on the stroma side of the thylakoid)

27
Q

How is water oxidized in the photosystems, and how is NADP+ reduced?

A
  • PSII excited electrons to take electrons H2O, generating PMF (not enough to reduce NADP+)
  • PSI re-energized the electron in order to reduce NADP+
28
Q

What is the Calvin (Dark) Reaction?

A
  • Occurs in the stroma
    1. Carboxylation (fixation)
    Input: 3 CO2 and RuBP (binds to enzyme rubisco) Output: produces 3PGA
    2. Reduction
    Input: 6 ATP (to phosphorylate 3 PGA), then 6 NADPH (to reduce 3 PGA to G-3P)
    Output: 6 ADP, then 6 NADP+
  • G-3P is produced which can be used to make carbohydrates or glucose
    3. Regeneration
    Input: 3 ATP (to regenerate RuBP)
    Output: 3 RuBP, with 3 ADP
29
Q

How is Cyclic Electron Transport used in the Calvin Cycle?

A
  1. The Calvin Cycle requires more ATP than NADPH
  2. Ferredoxin can reduce PQ instead of NADP+ reductase
  3. Electrons will flow from PQ to P700 in a circle to generate PMF to make ATP
    (80% of ETC use linear electron flow, 20% use cyclic electron flow
30
Q

What is the product of Photosynthesis?

A

G3P, which is converted into glucose
(G3P has 3 carbons so we need 2x G3P to make one glucose)

31
Q

The glucose made in photosynthesis can then be… (3 points)

A
  1. Used for glycolysis in the cytoplasm
  2. (if has enough energy) linked into polymers of starch (energy storage) or cellulose (cell wall)
  3. Used for the synthesis of other biomolecules
32
Q

How does Oxygenic Photosynthesis work in Prokaryotes?

A
  • No membrane-bound organelles, all metabolism occurs in the cytosol and on the cell membrane
  • Cyanobacteria have similar photosynthetic mechanism to chloroplast
  • Responsible for the oxygenation of Earth
33
Q

How does Anoxygenic Photosynthesis work?

A
  • Only known to occur in prokaryotic cells
  • Does not oxidize H2O
  • Evolved when oxygen was less abundant
  • Only use cyclic electron flow (does not produce O2, occurs in purple and green sulphur bacteria)

BIOL 241 (6 decks)

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