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Biology 1202 > Photosynthesis > Flashcards

Photosynthesis Flashcards

1
Q

What is the balanced chemical equation for photosynthesis?

A

6CO2 + 6H2O → C6H12O6 + 6O2

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2
Q

Chloroplasts are found where?

A

Mesophyll cells

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3
Q

What is the stomata?

A

The stomata are miscroscopic pores in the leaf where O2 exits and CO2 enters.

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4
Q

What occurs in the chloroplasts?

A

Both light reactions and the Calvin cycle occur within the chloroplast

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5
Q

What are major componants of the chloroplast?

A
  1. Membrane bound organelle
  2. Comprised of 3 membranes (outer, inner, and thylakoid membrane)
  3. Embedded in thylakoids - Light dependent reactions (proteins, pigments, electron transfer carriers, ATP synthase)
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6
Q

What occurs during photosynthesis’s redox reaction?

A
  • It is the reverse direction of electron flow compared to cell resp
  • Water is split and electrons are transferred to CO2
    -CO2 is the reduced to sugar
  • Water is oxidized
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7
Q

What are light dependent reactions?

A

Light dependent reactions - Convert solar energy to chemical energy. NADPH and ATP via photophsphorylation

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8
Q

What is the Calvin Cycle (light independent rxns)?

A

The calvin cycle - Incorporates CO2 from the atmosphere into organic molecules; it uses energy from light reactions to perform reduction

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9
Q

What are inputs and outputs of light dependent reactions?

A

Inputs - CO2
Outputs - O2

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10
Q

What are the inputs and outputs of the Calvin Cycle?

A

Inputs - CO2
Outputs - Sugar

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11
Q

Where do light reactions occur?

A

Thylakoid membrane

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12
Q

Where are photosystems (pigments), ETC proteins, and ATP sythase found?

A

Thylakoid Membrane

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13
Q

Where does the Calvin Cycle occur?

A

Stroma

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14
Q

Exciting Electrons: Photons are absorbed by clusters of pigment molecules in the?

A

Thylakoid membrane.

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15
Q

In chlorophyll a and b: Excited electrons from magnesium is in what ring?

A

Porphyrin ring.

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16
Q

Chlorophylls produce what pigments?

A

Chlorophylls produce green pigments (major photosynthetic pigment in plants, algae, and cyanobacteria)

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17
Q

Carotenoids produce what pigments?

A

Carotenoids produce yellow-orange pigments

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18
Q

What colour wavelengths of light are absorbed and used for photosynthesis?

A

Blue Light (450-495nm) - Absorbed
Red Light (620-750nm) - Absorbed
Green Light (495-570nm) - Reflected

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19
Q

What are photosystems?

A

Photosystems allow for organization of pigment molecules in the thylakoid membrane so energy transfer can be efficient. They are clusters of pigment-protein complexes that gather light energy and transfer it. (Contain: chlorophyll a, b, and carotenoid molecules)

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20
Q

What complex donates energy to the reaction centre through inductive resonance?

A

The antenna complex donates energy to the reaction centre through inductive resonance

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21
Q

What are the two photosystems?

A
  1. Photosystem I (PS 1): P700
  2. Photosystem II (PS 2): P680
22
Q

Name two routes for electron flow?

A
  1. Linear and Cyclic: Different roles
  2. Noncylcic (Linear): Produces both ATP and NADPH
23
Q

What is the process of noncyclic (linear) electron flow?

A
  • Photosystem II absorbs light and leaves the reaction centre oxidized when electrons leave
  • An enzyme extracts electrons from water and supplies them to the oxidized reaction centre to restore it back to ground state
    Electrons from PS II go through the ETC and end up at PSI
  • Another photon elevates that electron so it can be trapped as NADPH
    Makes EQUAL amounts of ATP and NADPH
24
Q

What are the 7 key plaayers in light reactions?

A
  1. PS II
  2. PSI
  3. PQ
  4. Plastocyanin
  5. NADPH
  6. Ferredoxin
  7. ATP synthase
25
What is the process of cyclic electron transport flow?
- PS I can function independently of PS II - Electron flow from ferrodoxin (fd) --> NADP+ reductase does NOT occur, so NO NADPH is produced - Purpose: Is to use light absorption to generate proton-motive force and generate ATP (photophosyphorlation) Used to make ATP only, no NADPH
26
A photosystem consists of?
A complex of pigment molecules such as chlorophyll bound to specific proteins
27
Which photosystem most directly produces NADPH?
Photosystem I
28
Oxygen is produced during photosynthesis when?
Water molecules are split to provide electrons for PS II
29
During photosynthesis, ATP molecules are generated directly by?
Chemiosmosis
30
What is the process of the Calvin Cycle?
- CO2 enters the cycle and leaves as a sugar - Cycles uses up ATP energy and electrons carried by NADPH to make organic molecules - Final product is a three-carbon sugar (G3P)
31
How many turns are required for once carbon, G3P, and glucose?
- 1 turn of the Calvin Cycle = 1 carbon - 3 turns of the Calvin Cycle = G3P - 6 turns of the Calvin Cycle = Glucose
32
What are the 3 phases of the Calvin Cycle?
1. Fixation 2. Reduction 3. Regeneration
33
What is the process of carbon fixation in the calvin cycle?
- Each CO2 molecule attatches to (RuBP; 5C) - This is catalyzed (RuBisCo) - The 6C splits in half to form (3-PGA) (6 3-PGA per 3CO2) - 15C + 3C = 18C
34
What is the process of reduction in the Calvin Cycle?
- Intermediates are energized by ATP & recieve electrons from NADPH - Input phase ii: 6 NADPH & 6 ATP - Pairs of electrons from NADPH reduce each 1,3 bisphospholycerate to G3P
35
What is the process of regeneration in the Calvin Cycle?
From fixation and reduction, having siz molecules of G3P (18C) after 3 turns - One of these ssix G3P (3C) is a net gain of carbohydrate, can exit the cycle and be used - Cannot use all G3Ps to make glucose because need to regenerate the orgiginal RuBP (3 x 5C) - Other five (15C) remain in cycle to regenerate 3 RuBP - Regeneration allows the system to be self-sustaining
36
The overall purpose of one turn of the Calvin Cycle is to?
Build organic molecules
37
What are the 3 methods of carbon fixation?
1. C3 pathway (3C, 3-PGA) 2. C4 pathway (4C, oxaloacetate) 3. CAM plants
38
Closing the stomata of a plant would result in what?
- Avoid dehydration (conserve water) - Interfere with photosynthesis - CO2 levels decrease - O2 levels increase - Promotes photorespiration
39
What happens when RuBisCo becomes "confused" in photorespiration?
- RuBisCo normally accepts CO2 but can become "confused" - Instead, O2 binds to the active site of CO2 and links to RuBP generating a wasteproduct = photorespiration - The wasteproduct must be rearranged and wastes ATP and NADPH in the process
40
Does photorespiration increase or decrease photosynthetic output from the Calvin Cycle?
Decreases by siphoning organic material from the Calvin Cycle
41
Photorespiration can drain how much of carbon fixation by the Calvin Cycle?
Photorespiration can drain away as much as 50% of carbon fixed by the Calvin Cycle on a hot, dry day (stomata closed)
41
What is the process of the C4 pathway?
- When O2 is high, C4 plants convert CO2 to malate - Mesophyll cells pump this 4C malate into bundle-sheath cells, where CO2 is released for use in Calvin cycle - RuBisCo is used to start the Calvin cycle, away from higher O2 contents near stomata
41
What are the main simalarities/differences between C4 and CAM?
- C4: Carbon fixation and the Calvin Cycle are spatially seperated - CAM: Carbon fixation and the Calvin Cycle are termporally seperated - Both add CO2 into organic intermediates before it enters the cycle, and both incorporate light energy into the production if sugar
42
What are key aspects of CAM plants?
CAM plants: Open stomata during the night and close them during the day - Temp is lower at night and humidiity is higher (less risk of dehydration)
42
In CAM plants, what happens at night vs the day?
Night: Stomata open; fix CO2 into variety of organic acids (malate) -O2 HIGH Day: Stomata closed; malate releases CO2 and used in Calvin Cycles - O2 LOW
43
Compare all 3 pathways (C3, CAM, and C4)
C3: Calvin cycle only CAM: Temporally seperated - Night and day C4: Spatially seperated - Converts CO2 to malate - Transports to bundle sheath cells; release CO2 for use in Calvin Cycle
44
What occurs in photorespiration?
The RuBisCo enezyme catalyzes the linkage of RuBP to O2, instead of CO2 causing a wate product.
45
True or False: In CAM photosynthesis, during the day CO2 is fixed to malate and store?
FALSE: During the day CO2 is not fixed as malate, this occurs at night
46
What is the enzyme that catalyzes the addition of 1 carbon of RuBP?
RuBisCO
47
Which two pathways do plants use to diminish photorespiration and water loss?
1. C4 photosynthesis 2. CAM

Biology 1202 (4 decks)

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