photosynthesis and stuff

Question 1

Photosynthesis

Answer 1

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

Question 2

2 sets of reactions involved in photosynthesis

Answer 2

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

Question 3

where does photosynthesis happen

Answer 3

chloroplast

Question 4

link between chloroplast and mitochondria

Answer 4

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!

Question 5

Light dependent reactions

Answer 5

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.

Question 6

Light INdependent reactions

Answer 6

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

Question 7

chloroplast (or lack thereof) in bacteria

Answer 7

• Bacteria do not have chloroplasts
• They have photosynthetic internal membranes

Question 8

purpose of Chloroplast

Answer 8

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

Question 9

how does the chloroplast make energy and why?

Answer 9

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

Question 10

where does the chloroplast make energy

Answer 10

Where? In the thylakoid membranes

Question 11

NADPH

Answer 11

• 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.

Question 12

how does NADH and NADPH differentiate between their roles

Answer 12

NADH = catabolic reactions
NADPH = anabolic reactions

Question 13

Z-scheme

Answer 13

the 2 photosystems used in hotophosphorylation

Question 14

what is the stroma analogous to in mitochrondia?

Answer 14

matrix

Question 15

what is thylakoid lumen analogous to in the mitochondria?

Answer 15

intermembrane space

Question 16

input and output during photosynthesis

Answer 16

Input:
photons and water

Output:
ATP, NADPH, O2

Question 17

where is atp synthesized during photosynthesis?

Answer 17

in the stroma

Question 18

Z-scheme

Answer 18

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!

Question 19

Light dependent reactions (phosphorylation)

Answer 19

photosystem II
1. Electrons are supplied by H2O

2. Light energy is required for PS II to “strip” the electrons from the water i.e. splitting water!
3. Electrons move along the ETC to provide energy to pump Protons (H+) into the lumen.
4. 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+

6. NADPH is synthesized in the stroma and will be used in the Calvin cycle.
7. ATP is synthesized in the stroma via chemiosmosis. H+ moves through the ATP synthase.

Question 20

input and output for photophosphorylation

Answer 20

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

Question 21

Oxygenic Photophosphorylation.

Answer 21

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

Question 22

Terminal Electron Acceptors in Photophosphorylation?

Answer 22

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

Question 23

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

Answer 23

• 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.

Question 24

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

Answer 24

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

Question 25

The Endosymbiont Theory

Answer 25

- 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

Question 26

where does the calvin cycle occur?

Answer 26

in the stroma of the chloroplast

Question 27

steps in the calvin cycle

Answer 27

1. carboxylation 2. reduction 3. regeneration of RuBP

Question 28

carboxylation in the calvin cycle

Answer 28

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

Question 29

reduction in calvin cycle

Answer 29

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

Question 30

regeneration in the calvin cycle

Answer 30

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.

Question 31

how do Photolithotrophs use CO2

Answer 31

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

Question 31

how do Photolithotrophs use CO2

Answer 31

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

Question 32

what enzyme catalyzes carbon fixation

Answer 32

Rubisco

Question 33

carbon fixation

Answer 33

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

Question 34

Fate of G3P/GAP/Triose Phosphates in the chloroplast

Answer 34

- 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

Question 35

INPUT AND OUTPUT FOR THE STUPID CALVIN CYCLE

Answer 35

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