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BIOL 112 > L26: Calvin Cycle > Flashcards

L26: Calvin Cycle Flashcards

1
Q

The stroma is like the ___ of the ____

A
  • Matrix, Mitochondria
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2
Q

Where does photosynthesis occur in bacteria?

A
  • Do not have chloroplasts

- Have photosynthetic internal membranes

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3
Q

What are the light dependant reactions?

A
  • Chloroplast needs to make lots of energy (ATP) and high energy intermediates (NADPH)
  • Water is oxidized to produce O2 (donates electrons to an ETC)
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4
Q

How do light dependant reactions occur?

A
  • Via an ETC called photophosphorylation
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5
Q

Why do light dependant reactions occur?

A
  • For the next set of reactions in the Calvin cycle
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6
Q

Where do light dependant reactions occur?

A
  • in the thylakoid membranes
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7
Q

What is going on with NADPH?

A
  • Similar to NADH but with an extra phosphate group
  • NADH = catabolic reactions, NADPH = anabolic reactions
  • Another high energy intermediate that is synthesized in photophos and then used in anabolic reactions
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8
Q

The Calvin Cycle is an __ __

A
  • Anabolic reaction
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9
Q

Photophos in a nutshell

A
  • cell uses the chloroplast to convert light energy into high energy intermediates such as ATP and NADPH
  • this is accomplished by photophos - an ETC
  • there are 2 photosystems and are often referred to as the Z-scheme
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10
Q

Why is it called a z-scheme?

A
  • photosystems II and I work together in the thylakoid membrane
  • hits of light provide energy
  • energy is used to pump protons across the membrane
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11
Q

What are the inputs and outputs of photophos?

A
  • Inputs: Photons, water, NADP+, ADP

- Outputs: ATP, NADH, O2

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12
Q

Where is ATP synthesized?

A
  • Stroma
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13
Q

Where is the ETC?

A
  • Thylakoid membranes
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14
Q

Is NADPH a TEA?

A
  • NO! NADP+ is an internal molecule and not from the environment.
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15
Q

What is step 1 of photophos?

A

Electrons are supplied by H2O

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16
Q

What is step 2 of photophos?

A

Light energy is required for PS2 to “strip” the electrons from the water

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17
Q

What is step 3 of photophos?

A

Electrons move along the ETC to provide energy to pump protons (H+) into the lumen

18
Q

What is step 4 of photophos?

A

an electrochemical gradient is created in the thylakoid lumen

19
Q

What is step 5 of photophos?

A

more light energy input at PSI. this energizes the electrons to drive the reduction of NADP+

20
Q

What is step 6 of photophos?

A

NADPH is synthesized in the stroma and will be used in the Calvin cycle

21
Q

What is step 7 of photophos?

A

ATP is synthesized in the stroma via chemiosmosis. H+ moves through the ATP synthase

22
Q

In the light-dependent reactions of photosynthesis, light energy is used to oxidize __ to ___

A

H2O to O2

23
Q

The electrons derived from H2O are used to reduce __ to ___ in the dependent reactions

A

NADP+ to NADPH

24
Q

Photophos summary

A
  • called the Z scheme
  • 2 photosystems work together to synthesize ATP and NADPH
  • light energy captured in the photosystems excites electrons to drive them through an ETC
  • the ETC creates a proton (H+) gradient for the synthesis of ATP
  • a second photosystem and ETC drives electrons to end up on high energy intermediate NADPH
25
Q

What is oxygenic photophos?

A
  • electrons from water reduce the PSII photosystem and release O2
  • oxygen is a product of the reaction and released
26
Q

Does photophos have a TEA?

A
  • NO!!!
  • NADP+, the electron acceptor, is a molecule found inside the cell, and is thus not by definition the TEA!
  • it’s just an electron acceptor
27
Q

Photosynthesis overview

A

LIGHT DEPENDENT REACTIONS:

  • water is oxidized to O2
  • NADP is reduced to form NADPH
  • ATP is synthesized via proton gradient driven by chemiosmosis

LIGHT INDEPENDENT REACTIONS:

  • ATP and NADP are used
  • CO2 is reduced to form carbohydrates
28
Q

Where is the H+ gradient created?

A

Thylakoid lumen

29
Q

Chloroplast and mitochondria equivalents.

A
  • thylakoid lumen = intermembrane space

- stroma = matrix

30
Q

What is the evidence that mitochondria and chloroplasts evolved from ancient prokaryotes?

A
  • both have double membranes
  • both have their own circular DNA (genomes)
  • both grow and multiply by binary fission - independently of the eukaryotic cell!
  • both have their own ribosomes, synthesizes proteins, etc
31
Q

Where does the Calvin Cycle Occur?

A

Stroma

32
Q

Photolithoautotrophs use __ as a carbon source and fix them into ___ ___

A

CO2, Organic molecules

33
Q

When something is fixed, it means that…

A
  • it is being converted from a gaseous state to a solid or liquid state
  • oxidized form → more reduced form
34
Q

Oxidized carbon vs reduced carbon

A

OXIDIZED: CO2

  • only C-O bonds
  • More strongly bonded

REDUCED: Cellular biomolecules

  • i.e. glucose, proteins, etc.
  • C-H bonds
  • less strongly bonded
35
Q

What are the 3 steps of the Calvin Cycle?

A
  • Carbon Fixation
  • Reduction
  • Regeneration
36
Q

What is the first step of the Calvin Cycle?

A

CARBON FIXATION:

  • each CO2 reacts with RuBP, producing two G3P molecules
  • the enzyme that catalyzes this reaction is called rubisco
  • the attachment of CO2 to an organic compound is called carbon fixation
37
Q

What is the second step of the Calvin Cycle?

A

REDUCTION:
the two 3-phosphoglycerate molecules are phosphorylated by ATP and reduced by NADPH to produce glyceraldehyde 3-phosphate (G3P or called GAP)

38
Q

What is the third step of the Calvin Cycle?

A

REGENERATION:

- the remaining G3P/GAP is used in ATP dependent reactions that regenerate RuBP

39
Q

How is the GAP/G3P (reduced carbon) related to CR?

A
  • notice that after the “glucose splitting” (step 5 of glycolysis) the substrate produced is G3P
  • the G3P from the Calvin cycle can enter glycolysis here
40
Q

What is the fate of GAP/G3P?

A

leaves the chloroplast and can be used in CR or used to build other macromolecules

41
Q

what are the inputs and outputs of the Calvin cycle?

A
  • Inputs: RuBP, CO2, NADPH, ATP

- Outputs: GAP, ADP, Pi, NADP+

42
Q

Calvin Cylce Summary

A
  • CO2 is oxidized
  • NADPH donates electrons for reducing C
  • GAP/G3P is reduced carbon
  • Used to build all other C-containing organic cellular molecules

BIOL 112 (23 decks)

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