Term
What is photosynthesis?
Briefly describe light reactions and dark reactions |
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Definition
Conversion of carbon dioxide to organic molecules using light energy
Light reactions : Capture light energy to synthesize NADPH and ATP
Dark reactions : Use electrons and protons of NADPH and the energy of ATP to turn C02 into carbohydrates.
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Term
Although photosystems have a P680 and P700 have maximum wavelengths (680 and 700 respectively) they still have a ____________.
Both Chlorophyll P680 and P700 have ___________ but they differ in absorbtion of light because of different _________________ and therefore __________. |
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Definition
Spectrum
Chlorophyll a
association with proteins and therefore electron distribution |
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Term
| NADP+ is oxidized by TWO H atoms. We know that one e- comes from the electron excited, where does the second one come from? |
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Definition
| The second electron comes from NADP+ reductase which holds an electron until the excited electron passes it |
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Term
| How does the excited electron from PSII get replaced? |
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Definition
The excited electron from PSII gets replaced from the oxidation of water.
H20 -> 2H^+1 + (1/2)02 + 2e-
H20 -> 2 electrons, 2 protons, 1/2 oxygen gas (02) |
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Term
| Oxygenic photosynthesis is the direct result of the developement of _______ |
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Definition
| Photosystem II, Photosystem II is the only natural thing that can oxidize H20 |
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Term
| The ________ or ________ of ______ results in protons getting pumped to the lumen in cyclic photophosphorylation. |
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Definition
| Reduction or oxidation of PQ |
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Term
What is rubisco? Is it the most important enzyme in the biosphere?
Is Rubisco the most abundant protein in the world? |
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Definition
Rubisco is Ribulose - 1,5 - biphosphate carboxylase oxygenase
Yes it is the most important enzyme in the biosphere
Rubisco catalyzes the reaction between RuBP and C02 to form 3GP
Yes, rubisco is the most abundant protein in the world. |
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Term
Explain the synthesis of rubisco.
What codes the large subunit of rubisco?
What codes the small subunit of rubisco?
Where are they coded? |
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Definition
The synthesis of rubisco requires coordination between nuclear genome and chloroplast genome.
Large subunit of rubisco is coded by the chloroplast genome, while the small subunit of rubisco is coded by the nuclear genome.
Large subunit synthesized in stroma
Small subunit synthesized in cystol and is transported to chloroplast where it associates with large subunit
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Term
| What is the problem with Rubisco? |
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Definition
They are catalytically VERY slow only 3-10 molecules of C02 catalyzed per second.
The active site of C02 can also bind to 02 (02 is a competitive inhibitor) -> Need ATP to convert to C02. |
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Term
Rubisco acts as both _________ and __________.
Explain the two |
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Definition
Carboxylase and Oxygenase
Carboxylase - Carbon gain
Oxygenase - Carbon loss
- Oxygen gain |
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Term
What is photorespiration?
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Definition
Photorespiration is when 02 binds to Rubisco, which causes Rubisco to turn 02 into C02.
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Term
When photorespiration happens, light dependant reaction _____________
Light independant reactions ______________
Photosynthesis significantly _______ photosynthetic efficiency |
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Definition
Light dependant reactions remain unchanged
Light independant reactions are left "undone"
- Instead of making C02 into carbs, C02 is released!
Reduces |
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Term
| List the process of photorepiration |
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Definition
1) In Chloroplasts -> O2 + RuBP = Glycolate + 3PG
2) In peroxisome -> Glycolate diffuses in peroxisome and is turned into glycine
3) In mitochondria -> Glycine turns to C02 and serine, C02 released |
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Term
Describe the leaf anatomy
What does the stomata do? |
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Definition
Leaf : 1) Large surface area
2) Waxy Cuticle
3) Has stomata (surface pores)
Stomata help regulate gas exchange
- Delicate balance between minimizing water loss and regulating gas exchange |
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Term
C3 plants favour photorespiration under 3 conditions :
1) High temperature
2) Low C02 concentration
3) High 02 concentration
What happens to plants when its hot? |
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Definition
| When its hot, stomata close to lower water loss. This also reduces gas exchange - Lowers C02 levels and 02 levels accumulate for photorespiration. |
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Term
| As temperature increases : Photorespiration takes away a ___________ amount of carbon |
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Definition
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Term
| Adaptation to minimize photorespiration : Give one example |
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Definition
Algae pump C02 into cells.
Takes HC03-, converts it to C02 and pumps C02 into cell. |
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Term
What are alternative photosynthetic pathways that plants in tropical climates use?
How do they use it? |
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Definition
1) C4 Pathway - Uses spatial separation
2) CAM Pathway - Uses temportal seperation
They use it via different plant leaf anatomy |
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Term
C4 plants : How do they bypass photorespiration?
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Definition
C4 plants raise the C02 levels over 02 levels so that carboxylase functions by rubisco is favoured.
C4 plants also use an alternative enzyme called PEP carboxylase that have a high affinity for C02 and lacks oxygenase activity |
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Term
| List the characteristics of C4 plants |
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Definition
High affinity for C02
Primary C02 acceptor is PEP
Primary C02 fixing enzyme is PEP Carboxylase
First product formed from C02 is Oxaloacetate (4C)
Has two photosynthetic cells in leaf : Mesophyll and bundle sheath cells |
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Term
| CAM plants : What are they? List characteristics. |
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Definition
Crassulean Acid Metabolism plants
They operate like C4 plants but use temporal sensation
Stomata open at night to release 02 and allow C02 in, C02 fixed into malate
Stomata close during day - To prevent water loss as well as to prevent gas exchanges
Malate is turned to pyruvate and C02 is released.
-> Maximizes Calvin cycle by favouring Carboxylase activity of Rubisco |
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