Photosynthesis

Question 0

Pigment that makes leaves green, absorbs light principally in the violet and the blue wavelengths and also in the red, and reflects green light

Answer 0

Chlorophyll

Question 1

Process involving conversion of the energy present in sunlight to energy present in organic molecules

Answer 1

Photosynthesis

Question 2

Primary photosynthetic pigment that comprises about 75% of the total chlorophyll in most plants.
It is also found in all photosynthetic eukaryotes and blue-green algae.

Answer 2

Chlorophyll a

Question 3

Difference between chlorophyll a and chlorophyll b structure.

Answer 3

Chlorophyll b has -CHO group in place of the -CH3 group of chlorophyll a

Question 4

Accessory pigment that transfers energy to chlorophyll a during photosynthesis; accounts for 25% of the total chlorophyll

Answer 4

Chlorophyll b

Question 5

Accessory pigment that replaces chl b in some algae, specifically brown algae

Answer 5

Chlorophyll c

Question 6

Accessory pigments that are not chlorophyll:

Answer 6

Carotenoids (Carotenes and xanthophylls)

Phycobilins

Question 7

2 major process of photosynthesis

Answer 7

Light reactions and carbon fixation reactions

Question 8

Light reactions happen where?

Answer 8

Thylakoid membrane

Question 9

Carbon fixation happens where?

Answer 9

Stroma

Question 10

What happens during light reactions?

Answer 10

• Energy from sunlight is converted to electron flow
• oxygen is released as a byproduct
• products are ATP and NADPH
• comprise of 2 photosystems

Question 11

Light harvesting components of the photosystems. It has pigment molecules that gather light energy and “funnel” it to the reaction center

Answer 11

Antennae complex

Question 12

Photosystems consist of:

Answer 12

Antennae complexes
Reaction center chlorophylls
electron transport proteins

Question 13

Special chlorophyll a molecules of the rxn center in Photosystem I

Answer 13

P700

Question 14

Special chlorophyll a molecules of the rxn center in Photosystem II

Answer 14

P680

Question 15

What happens in photosystem II?

Answer 15

1. Light energy (2 photons) enters PII and is trapped by pigment molecules and passed to P680 of rxn center.
2. Energized electrons are transferred from P680 to an electron acceptor.
3. As the electrons are removed from P680, they are replaced by low-energy e- from water molecules and oxygen is produced (photolysis)
4. Pairs of electrons pass down downhill to photosystem I along ETC

Question 16

Factors that contribute to protomotive force

Answer 16

Concentration gradient and charge separation

Question 17

Potential energy that contributes to the production of ATP via the ATP synthase using the proton gradient

Answer 17

Protomotive force

Question 18

Function is to split water (which contributes to the proton gradient) and it also steals 2 electrons, which then are donated to rxn center to replace the electrons lost;
Essential cofactor is manganese

Answer 18

Oxygen evolving complex

Question 19

Which part of PII pumps protons across the membrane, generating the proton gradient?

Answer 19

Cytochrome b/f

Question 20

What happens in photosystem I?

Answer 20

1. Light energy is absorbed and passed to P700 of the reaction center.
2. The energized electrons are accepted by coenzyme NADP+, and electrons removed from P700 are replaced by electrons from photosystem II
3. Passing of electrons down carriers reduces NADP+ to NADPH

Question 21

Unidirectional flow of electrons from water to NADP+

Answer 21

Noncyclic electron flow

Question 22

What does linear electron transport produces?

Answer 22

1 ATP and 1 NADPH

Question 23

What does cyclical electron transport/flow generates?

Answer 23

Only ATP

Question 24

How does cyclical electron transport work?

Answer 24

Ferrodoxin transports 2 electrons back to cyt b/f

This results in translocation of 2 protons

Question 25

This process require the products of the light reactions and where carbon fixation occurs

Answer 25

Calvin cycle

Question 26

What happens during Calvin cycle?

Answer 26

1. A molecule of CO2 combines with a 5-C sugar (RuBP) to form two molecules of 3-C compound (PGA).
2. PGA is then reduced to 3-C molecule PGAL, with electrons provided by NADPH and energy by ATP.
3. At each turn of the cycle, one carbon atom enters the cycle, and RuBP is regenerated.
4. Fixed carbon is also generated to convert to either sucrose or starch

Question 27

Ratio of the use of ATP and NADPH during Calvin cycle

Answer 27

3:2

Question 28

Process by which the oxygenase activity of rubisco combined with the salvage pathway consumes O2 and releases CO2

Answer 28

Photorespiration

Question 29

Difference between C4 and C3 plants

Answer 29

C3 only uses Calvin cycle , C4 uses C4 pathway and Calvin cycle

Question 30

What happens during C4 pathway?

Answer 30

1. Oxaloacetate is formed when CO2 is fixed to PEP in a reaction catalyzes by PEP carboxylase found in the mesophyll.
2. Oxaloacetate is then reduced to malate or aspartate
3. The malate/aspartate is moved to the bundle-sheath cells where it is decarboxylated to yield CO2 and pyruvate.
4. CO2 is then used for Calvin cycle

Question 31

Difference between CAM and C4 plants.

Answer 31

Cam plants have time separation

C4 has spatial separation of the two pathways (c4 and Calvin cycle)

Question 32

What happens during CAM photosynthesis?

Answer 32

1. CO2 is fixed in the dark through activity of PEP carboxylase in the cytosol
2. Oxaloacetate is produced, then reduced to malate.
3. Malate is stored as malic acid in the vacuole.
4. During the day, malic acid is recovered from the vacuole, decarboxylated and CO2 is transferred to RuBP of the Calvin cycle w/in the same cell