4

Question 1

Fates of Excited electrons? 3•

Answer 1

•Fluorescence: They eventually return to a lower energy state

•Resonance: transfer of energy (not electrons) between adjacent pigments

•Photochemistry (redox reactions): transfer of electrons to acceptor molecules. Pigments become oxidized, acceptor molecules become reduced.

Question 2

Antenna complex?

Answer 2

Contains pigment molecules that capture and direct energy from protists towards the reaction Center. Both chlorophylls have it.

Question 3

Plants can adjust how much light they get. How?

Answer 3

They adjust the concentration of chlorophyll.

Question 4

When does photochemistry commonly occur?

Answer 4

When electrons go from the photosystem (gets oxidized) and travels to the electron acceptor (gets reduced).

Question 5

Reaction center 2 vs reaction center 1?

Answer 5

RC2: Accepts electron from protons produced from the splitting of water, and that electron flows to Pheophytin, which reduces pheophytin.

RC1: Accepts electron from photosystem 2 to RC1, and brings that electron to Ferredoxin, which reduces it.

Question 6

How does reaction center 2 obtain the electron after being oxidized?

Answer 6

From the splitting of water which a proton releases an electron and travels to reaction center 2, which then travels to pheophytin.

Question 7

How does reaction center 1 reobtain an electron after being oxidized?

Answer 7

The electron comes from reaction center 2.

Question 8

How many electrons get passed to photosystem 2 and 1?

Answer 8

1 electron, even if it shows more.

Question 9

The linear scheme (Z-scheme) of photosystem?

Answer 9

The shape of arrows representing the amount of energy through ETC, it looks like the letter, Z. However, there is higher energy when electron is at photosystem 1 (P700) than photosystem 2 (P680).

Question 10

Photosystem 2 not only passes the electron in photosystem 1, but does something else?

Answer 10

Pumps protons and electrons from the stroma to the lumen to contribute to the electrochemical gradient.

Question 11

Plastoquinone (PQ)?

Answer 11

Transports protons from the stroma to the lumen, and transports electrons from photosystem 2 to 1.

Question 12

The ATP produced by the chloroplast is ONLY used by?

Answer 12

The chloroplast

Question 13

Plastocyanin (PC)?

Answer 13

Electron carrier that links PS2 to and PS1 by donating electrons from PS2 to the reaction center of PS1.

Question 14

Cyclic scheme of photophosphorlyation?

Answer 14

Instead of electrons flowing through the Z-scheme, it goes back to PQ after going through PS I since plants don’t always need NADPH but still needs ATP.

It will also follow that scheme to avoid excess O2 accumulation from PS II.

Question 15

Where does the Calvin cycle occur?

Answer 15

In the stroma.

Question 16

Three steps of Calvin cycle? 3•

Answer 16

•Carbon fixation
•Reduction
•Substrate Regeneration

Question 17

How many cycles to get 1 G3P?

Answer 17

3

Question 18

G3P two fates?

Answer 18

•20% of it go to make glucose
•80% of it goes to regenerate the substrate -> RuB

Question 19

RubisCO (Ribulose-1,5-bisphosphate carboxylase/oxygenase)?

Answer 19

An enzyme that catalysis the reaction of carbon fixation.

Question 20

There is a competition between O2 and CO2 at the active site of RubisCO. What happens?

Answer 20

RubisCO catalysis two opposite competing reactions, one with CO2 (carbon fixation) and the other with O2 (photorespiration).

Question 21

At the end of photorespiration, what is produced?

Answer 21

Oxidation of PGA to PG and heat.

Question 22

Does photorespiration contribute to the Calvin cycle?

Answer 22

No, only carbon fixation.

Question 23

RubisCO has a very slow reaction rate and low ______ binding affinity?

Answer 23

CO2

Question 24

Why is RubisCO such a poor catalyst?

Answer 24

•Competition of catalyzing either CO2 or O2
•Very low reaction rate
•Low CO2 binding affinity

Question 25

How do photosynthetic organisms cope with a poor C-fixing catalyst? •2

Answer 25

•Synthesizing a lot of RubisCO
•Concentrating CO2 around RubisCO (C4 and CAM carbon concentrating mechanisms make photosynthesis more efficient)

Question 26

C4 Plants?

Answer 26

One CO2 molecule inside the mesophyll cells become phosphoenolpyruvate (PEP) which then becomes 4 carbon organic acids, malate. This is supported by the enzyme, PEP Carbonxylase. Malate travels to the bundle sheath cells and goes next to rubisco. Malate breaks down into pyruvate and CO2 ensuring that it brings a high concentration of CO2 next to the rubisco.

Question 27

How do molecules get transported within the plant organism?

Answer 27

Through a channel called a Plasmodesmata that connects the cytosols between cells.

Question 28

Malate (4 carbons compound) to shuttle CO2 to the bundle sheath cells. It requires more/less ATP?

Answer 28

More

Question 29

Crassulacean acid metabolism (CAM)?

Answer 29

In CAM, Rubisco activity occurs in the mesophyl cells. CO2 is converted to Crassulacean Acid trapped in a vacuole during the night. During the day, the Calvin cycle starts by releasing a high concentration of CO2 near rubisco.

Question 30

When the electron acceptor (Pheophytin and Ferredoxin) become reduced, electromagnetic energy is transformed to?

Answer 30

Chemical energy.

Question 31

How many cycles required to fix one CO2 molecule?

Answer 31

1

Question 32

C3 photosynthesis?

Answer 32

The build of the 3-PGA molecule after carbon fixation since 3-PGA has three carbons.

Question 33

Carbon Fixation reaction?

Answer 33

3RuBP + 3CO2 -> 6 3-PGA, catalyzed by Rubisco

Question 34

Reduction reaction?

Answer 34

6 3PGA + 6ATP + 6NADPH -> 5 G3P (to regeneration) + 1 G3P (for glucose formation)

Question 35

Regeneration formula?

Answer 35

5 G3P + 3ATP -> 3RuBP

Question 36

In C4 photosynthesis, where is the Calvin cycle located?

Answer 36

The bundle sheath cell under the mesophyll cell.

Question 37

In C3 photosynthesis, where does the Calvin cycle occur?

Answer 37

Inside the mesophyll cell.

Question 38

Why is CAM important?

Answer 38

This is so CO2 can ONLY enter the plant at night, during colder temperatures and less dehydration (stomata open). However at night, they can keep their stomata closed to reduce the chances of dehydrating.

Question 39

How does electromagnetic energy get converted into chemical energy?

Answer 39

Light gets absorbed by the pigments in the antenna complex, which then transfers it to two specialized chlorophyll molecules in the reaction center, energizing the pigment and exciting that electron. However, electrons in its excited state must transfer their energy via resonance as soon as possible. It reduces the electron acceptor, increases potential energy, which creates chemical energy.

Question 40

How does cyclic electron flow affect PSII?

Answer 40

Since its the same electron bouncing around PSI, a new electron is not needed and PSII halts.