*Photosynthesis

Question 1

what is photosynthesis?

Answer 1

converting light to chemical energy

Question 2

what is the equation for photosynthesis?

Answer 2

6CO2 + 6H2O –> C6H12O6 + 6O2

Question 3

what is one significant thing about photosynthesis for animals?

Answer 3

photosynthesis causes an increase in atmospheric oxygen

Question 4

give 5 things that photosythesis plays a big role in

Answer 4

• the global carbon cycle
• rise of atmospheric oxygen
• food (Everything we eat comes directly or indirectly from plants)
• fuel/biofuel (Plants have been a key source of energy over tens of thousands of millennia)
• theraputic drugs

Question 5

give 2 examples of theraputic drugs that come from plants

Answer 5

• Salicylic acid isolated from bark for production of aspirin
• Vinblastine and vincristine for treatment of leukemia and Hodgkin’s lymphoma

Question 6

where in the plant does photosynthesis occur?

Answer 6

the chloroplasts

Question 7

what are the 3 key components in light reactions?

Answer 7

• pigments
• photosystems
• electron transport chain

Question 8

state how pigments play a role in photosynthesis

Answer 8

Photosynthetic pigments absorb the light that powers photosynthesis

Question 9

what is chlorophyll a?

Answer 9

• Green pigments found in plants, algae and cyanobacteria
• Absorbs light that powers photosynthesis through the excitation of electrons located in the porphyrin-like ring
• Make up an antenna complex that is associated to a photochemical reaction centre, forming a photosystem

Question 10

what is the difference between chlorophyll a and b?

Answer 10

Chlorophyll b has the same structure as chlorophyll a but the CH3 is replaced by an aldehyde group (-CHO) and absorbs at 500 – 640 nm (appearing olive green)

Question 11

what are carotenoids?

Answer 11

• Carotenoids are yellow, orange, red or brown pigments
• Absorb strongly in the blue-violet range
• Known as accessory pigments (along with chlorophyll b)
• Pass absorbed light energy to chlorophyll a
• Provide photoprotection

Question 12

what are the 3 pigments present in photosynthesis?

Answer 12

• Chlorophyll a (Primary photosynthetic pigment)
• Chlorophyll b (Accessory pigment)
• Carotenoids (Accessory pigment, Primary function is to prevent oxidative damage of chlorophyll during photosynthesis)

Question 13

what are the 3 possible options of what happens to the energy after it has been absorbed as light?

Answer 13

• Converting extra energy to heat or to a combination of heat and light
• Transferring energy to a neighbouring chlorophyll molecule – resonance energy transfer
• Transferring from a negative charged high-energy electron to another nearby molecule (electron acceptor)

Question 14

what is the electron transport chain?

Answer 14

• Light energy drives the synthesis of both ATP and NADPH
• The oxygen evolving complex catalyzes the splitting of two water molecules (photolysis)
• The proton gradient drives the ATP synthase to generate ATP (photophosphorylation)

Question 15

what is the photolysis equation?

Answer 15

2H2O –4 photons–> 4H+ +O2 + 4e-

Question 16

what is the function of the cyclic electron flow?

Answer 16

To generate more ATP without making NADPH (Important as ATP source in the bundle sheath chloroplasts of some C4 plants and used in bacterial photosynthesis)