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BIOL 112 > photosynthesis and stuff > Flashcards

photosynthesis and stuff Flashcards

1
Q

Photosynthesis

A

the conversion of light energy to chemical energy (stored in the bonds of carbohydrates)

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2
Q

2 sets of reactions involved in photosynthesis

A
  1. Light dependent reactions. (photophosphorylation)
  2. Light independent reactions. (calvin cycle, uses energy from the first set of reactions)
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3
Q

where does photosynthesis happen

A

chloroplast

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4
Q

link between chloroplast and mitochondria

A

Carbohydrates (reduced forms of carbon) are produced by the chloroplast from CO2.

The sugars then undergo catabolism (e.g. cellular respiration) to produce energy in the mitochondria!

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5
Q

Light dependent reactions

A

photophosphorylation
- Cell uses the chloroplast to convert light energy into high energy intermediates such as ATP and NADPH.
- an electron transport chain which creates a proton (H+) gradient for synthesis of ATP
- a second photosystem and ETC drives electrons. end up on high energy intermediate NADPH
- There are 2 photosystems and are often referred to as the Z-scheme.

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6
Q

Light INdependent reactions

A
  • Calvin cycle uses these ATP and NADPH to synthesize organic carbon from inorganic CO2.
  • This is also called carbon fixation.
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7
Q

chloroplast (or lack thereof) in bacteria

A
  • Bacteria do not have chloroplasts
  • They have photosynthetic internal membranes
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8
Q

purpose of Chloroplast

A

Chloroplast needs to make lots of energy (ATP) and high energy intermediates (NADPH).

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9
Q

how does the chloroplast make energy and why?

A
  • How? via an Electron Transport Chain (ETC) called Photophosphorylation.
  • Why? For the next set of reactions in the Calvin cycle.
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10
Q

where does the chloroplast make energy

A

Where? In the thylakoid membranes

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11
Q

NADPH

A
  • Another high energy intermediate that is synthesized in Photophosphorylation and then used in anabolic reactions
  • Similar to NADH but with an extra phosphate group.
  • Having NADH and NADPH in the cell allows the cells to differentiate between the 2 electron carriers and their roles.
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12
Q

how does NADH and NADPH differentiate between their roles

A

NADH = catabolic reactions
NADPH = anabolic reactions

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13
Q

Z-scheme

A

the 2 photosystems used in hotophosphorylation

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14
Q

what is the stroma analogous to in mitochrondia?

A

matrix

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15
Q

what is thylakoid lumen analogous to in the mitochondria?

A

intermembrane space

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16
Q

input and output during photosynthesis

A

Input:
photons and water

Output:
ATP, NADPH, O2

17
Q

where is atp synthesized during photosynthesis?

A

in the stroma

18
Q

Z-scheme

A

the 2 photosystems used in photophosphorylation

  • Large increase in energy as electrons pass through each of the two photosystems
  • overall decrease in energy occurs as electrons move between the two photosystems
  • energy trajectory looks like a Z!
19
Q

Light dependent reactions (phosphorylation)

A

photosystem II
1. Electrons are supplied by H2O

  1. Light energy is required for PS II to “strip” the electrons from the water i.e. splitting water!
  2. Electrons move along the ETC to provide energy to pump Protons (H+) into the lumen.
  3. An electrochemical gradient is created in the thylakoid lumen

photosystem I
5. More Light energy input at PSI. This “energizes” the electrons to drive the reduction of NADP+

  1. NADPH is synthesized in the stroma and will be used in the Calvin cycle.
  2. ATP is synthesized in the stroma via chemiosmosis. H+ moves through the ATP synthase.
20
Q

input and output for photophosphorylation

A

Input: photons and water
Output: ATP, NADPH, O2

21
Q

Oxygenic Photophosphorylation.

A

Electrons from water (H2O) reduce the PSII photosystem and release O2.
= “Oxygenic” (oxygen is a product of the reaction and released)

22
Q

Terminal Electron Acceptors in Photophosphorylation?

A

NOPE
The electrons end up on a molecule that is already present in the chloroplast i.e NADP +

23
Q

why is NADP+ not a terminal electron acceptor and what is it instead?

A
  • NADP+ accepts the electrons in photophos to become NADPH.
  • Since this is a molecule found inside the cell, it is NOT by definition a “TERMINAL electron acceptor” – it is an “final electron acceptor”.
  • The word “terminal” refers to a molecule that has been taken up by the cell from the environment e.g. O2 as in oxphos.
24
Q

input and output for Light independent reactions: calvin cycle = carbon fixation

A
  • ATP and NADPH are used
  • CO2 is reduced to form carbohydrates
25
Q

The Endosymbiont Theory

A
  • Mitochondria & Chloroplast evolved from ancient prokaryote

Like bacterial cells, they:
- Both have double membranes.
- Both have their own circular DNA (genomes) o Both grow and multiply by binary fission –
independently of the eukaryotic cell!
- Both have their own ribosomes, synthesizes proteins
etc

26
Q

where does the calvin cycle occur?

A

in the stroma of the chloroplast

27
Q

steps in the calvin cycle

A
  1. carboxylation
  2. reduction
  3. regeneration of RuBP
28
Q

carboxylation in the calvin cycle

A
  • Each CO2 reacts with ribulose bisphosphate (RuBP), producing two 3-phosphoglycerate (3-PG) molecules. - The enzyme that catalyzes this reaction is called Rubisco.
29
Q

reduction in calvin cycle

A

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

30
Q

regeneration in the calvin cycle

A

regeneration of RuBP
3-carbon compounds are reorganized and combined to produce RuBP
The remaining G3P/GAP/triose phosphates is used in ATP dependent reactions that regenerate RuBP.

31
Q

how do Photolithotrophs use CO2

A

as a carbon source and fix them into organic molecules (reduced forms of carbon).

31
Q

how do Photolithotrophs use CO2

A

as a carbon source and fix them into organic molecules (reduced forms of carbon).

32
Q

what enzyme catalyzes carbon fixation

A

Rubisco

33
Q

carbon fixation

A

The attachment of CO2 to an organic compound is called carbon fixation.

34
Q

Fate of G3P/GAP/Triose Phosphates in the chloroplast

A
  • GAP/ Triose Phosphates leaves the chloroplast.
  • These reduced forms of carbon can now be used in cellular respiration (cytosol, mitochondria)
    OR be used to build other macromolecules
35
Q

INPUT AND OUTPUT FOR THE STUPID CALVIN CYCLE

A

Input: CO2, NADPH, ATP
Output: G3P, ADP, Pi, NADP+

BIOL 112 (25 decks)

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