BSCI 170 > Final Exam > Flashcards

Final Exam Flashcards

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1
Q

What does photosynthesis consist of?

A

Light reactions and the Calvin Cycle (carbon fixation), and converting light energy to chemical energy.

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2
Q

Where does photosynthesis occur?

A

The chloroplasts (eukaryotic cells).

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3
Q

Where do light reactions occur?

A

The thylakoids (with membrane associated proteins).

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4
Q

Where does the Calvin cycle occur?

A

The stroma (space enclosed by inner membrane)

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5
Q

What do light reactions consist of?

A

Redox Reactions
Electron transport chain
ATP synthesis using proton gradient

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6
Q

What happens during light reactions?

A

Reduction of electron acceptor NADP+ to NADPH
Generate ATP from ADP by photophosphorylation
Split H20 and release 02

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7
Q

Where does the generation ATP from ADP by photophosphorylation happen?

A

Photosystem 2

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8
Q

Where does the reduction of the electron acceptor NADP+ happen?

A

Photosystem 1

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9
Q

What is photophosphorylation (why is it called that)?

A

Where light energy is used to create ATP during photosynthesis. Name comes from where the energy is obtained (IE light; photons).

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10
Q

What are the basic parts of the Calvin cycle?

A

ATP and NADPH are converted to CO2
CO2 is converted to organic compounds (G3P)
G3P is converted to organic sugars or regenerated

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11
Q

Where does the splitting of H20 and release of O2 occur?

A

Photosystem 1

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12
Q

What is the overall goal of light reactions?

A

Generate things that can be used in carbon fixation reactions (ATP, NADPH)

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13
Q

Describe the energy levels of short and long wavelengths.

A

Short wavelengths: More energy
Longer wavelengths: Less energy

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14
Q

What happens when photons interact with the components of light reactions and are absorbed?

A

Energy is transferred to the compound (electrons).

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15
Q

Describe the process of an electron absorbing light energy (photon).

A
  1. Electron absorbs energy at ground state
  2. Electron moves to excited state
  3. Electron returns to ground state releasing energy
  4. Adjacent electrons absorb released energy
  5. Process continues until photo reaches reaction center
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16
Q

What is a pigment?

A

Substances that can absorb visible light at specific wavelengths:
Chlorophyll A
Chlorophyll B
Carotenoids

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17
Q

What is a photosystem?

A

A large complex of transmembrane proteins and pigments. Composed of two multi-protein complexes.

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18
Q

What are the two components of a photosystem?

A

Light harvesting complex and reaction center.

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19
Q

Define the light harvesting complex.

A

A complex of photosynthetic pigments bound to transmembrane proteins, surrounds the reaction center.

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20
Q

Define the reaction center.

A

Transmembrane proteins and very specific chlorophylls.

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21
Q

What are the two types of photosystems and why are they different?

A

Photosystem 1 and 2. They are different due to the types of chlorophylls found in them.

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22
Q

PS1 chlorophylls absorb light at what?

A

700nm

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23
Q

PS2 chlorophylls absorb light at what?

A

680nm

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24
Q

Light Reactions of Photosynthesis Step 1:

A

Photon of light is absorbed, energy is transferred to electrons in a pigment. Occurs in light harvesting complex.

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25
Light Reactions of Photosynthesis Step 2:
Energy lost in step 1 is absorbed by other electrons. Energy relay occurs until energy reaches reaction center chlorophylls.
26
Light Reactions of Photosynthesis Step 3:
Light energy transferred to reaction center chlorophylls is converted to electron acceptors (excited electrons are transferred to electron acceptor).
27
Light Reactions of Photosynthesis Step 4:
Electron acceptors move into electron transport chain.
28
Reaction center chlorophylls are what?
Oxidized (essentially by light energy).
29
Primary electron acceptors are what?
Reduced (essentially by light energy).
30
Which photosystem requires more energy to excite electrons in reaction center chlorophylls?
PS2 (680nm wavelengths = more energy)
31
What is the concentration of [H+] in the thylakoid space?
High [H+]
32
What is the concentration of [H+] in the stroma?
Low [H+]
33
Exergonic electron transfer reactions are coupled to what?
Movement of H+ into thylakoid space.
34
Diffusion of H+ into stroma is couples with what?
ATP synthesis
35
Describe the process of photophosphorylation.
Electron acceptor enters chain and is oxidized Through a series of redox reactions protons will be moved into thylakoid space. Proton gradient is eventually set up for ATP synthesis.
36
Which photosystems generates NADPH and which photosystem generates ATP during linear electron flow?
PS1: NADPH PS2: ATP
37
Describe the basic process that happens in photosystem 2.
Light energy is used to transfer electrons from reaction center chlorophylls to the electron acceptor. Exergonic electron transfer reactions are coupled to movement of H+ into the thylakoid space. Exergonic movement of H+ into stroma is coupled with ATP synthesis.
38
How are light reactions in PS1 different from PS2?
Electrons in the electron transport chain are reduced to NADPH.
39
How are electrons from reaction center chlorophylls replaced (PS1)?
Reaction center chlorophylls are reduced.
40
Describe linear electron flow in light reactions.
Electrons from PS2 reaction center chlorophylls are eventually transferred (used to replenish) PS1 reaction center chlorophylls.
41
How are electrons in PS2 replenished?
Water is oxidized and electrons are transferred to PS2.
42
What is the main goal of the Calvin cycle?
Convert 6 CO2 molecules to organic compounds.
43
Carbon Fixation Main Product/ Main Goal
Combine ribulose 1-5 bisphosphate with CO2 to get: 2 molecules of 3 phosphoglycerate (3PG).
44
What are the 3 main parts of the Calvin cycle?
Carbon Fixation Reduction Regeneration
45
What are the two steps of carbon fixation?
1. Ribulose 1-5 bisphosphate is combined with CO2 to form a 6c compound. 2. The 6c compound is immediately split into two 3 phosphoglycerate (3PG)
46
What carries out the two steps of carbon fixation?
Rubisco (ribulose bisphosphate carboxylase/oxygenase)
47
Reduction Main Product/ Main Goal.
Reduce 3 phosphoglycerate to glyceraldehyde 3 phosphate
48
What are the steps of reductions? hint* 3 steps
1. 3 phosphoglycerate is reduced to G3P 2. Uses NADPH (NADPH is oxidized to NADP+) 3. G3P is either transported to cytosol and used to synthesize sugars or is used for regeneration.
49
Regeneration Main Product/Goal/Step
G3P is converted back to ribulose 1-5 bisphosphate.
50
What parts of the Calvin cycle use ATP?
Reduction and Regeneration.
51
What parts of the Calvin Cycle use NADPH?
Reduction
52
Describe the basic flow of linear electron flow.
H20-> PS2 chlorophylls-> primary electron acceptors-> PS1 chlorophylls-> primary electron acceptors-> NADPH.
53
How much ATP and NADPH are needed to fix 1 molecule of CO2?
3 ATP and 2 NADPH.
54
Cyclical electron flow.
Generates only ATP, electrons from PS1 enter different electron transport chain. *Electrons are cycled back to reaction center chlorophylls.
55
Why do plants use cyclical electron flow?
To generate more ATP if needed.
56
What is oxygenase activity of rubisco?
When rubisco interacts with O2 instead of CO2.
57
What happens when rubisco interacts with o2 rather than co2?
3 phosphoglycerate and 2 phosphoglycolate are generated. 3PG will continue in cycle but 2PG will not and needs to be recycled back into Calvin cycle-energetically costly.
58
What is photorespiration and what are its effects?
When there is oxygenase activity of rubisco causing 2PG to be recycled into Calvin cycle. Reduces photosynthetic efficiency.
59
When does photorespiration become an issue?
When O2 level rise.
60
What is the stomata and how does it function in plants?
Pore used for gas exchange. Plants close the stomata in hot weather to reduce H20 loss, but it increases O2 build up.
61
Describe C4 plants.
2 Separate fixation reactions Specialized leaf structures: mesophyll cells bundled sheath cells
62
What are the steps C4 plants take to reduce photorespiration?
1. Co2 is initially combined with a 3c compound to form a 4c compound in the mesophyll cells. 2. 4c compound enters bundle sheath cells and is decarboxylated. 3. CO2 is released in bundle sheath cells and enter Calvin Cycle. 4. 3c compound is regenerated in mesophyll cells.
63
What do the two separate carbon fixation reactions do in C4 plants?
Concentrate Co2 in the bundle sheath cells w/ rubisco Promote carboxylase activity of rubisco.
64
Describe CAM (Crassulacean Acid Metabolism) Plants.
2 separate carbon fixation reaction Keep stomata closed during the day and open at night
65
What are the steps CAM plants take to reduce photorespiration?
1. At night CO2 is combined w/ a 3c compound, makes 4c 2. 4c compound is stored in vacuole until daytime 3. At daytime 4c compound is split into Co2 and 3c 4. Co2 enters Calvin Cycle 5. 3c compound is combined with Co2 at night.
66
How are CAM plants different from C4 plants?
The two separate reactions are temporally separated not spatially into different cells. All reaction occur in the same cell.
67
In light reactions electrons move from which PS to which PS?
PS2 to PS1
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