Energy production: photosynthesis and mitochondria

Question 1

what are the three main uses of plants and photosynthesis?

Answer 1

• 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
• therapeutic drugs

Question 2

what are the two reactions that happen during photosynthesis?

Answer 2

• stage 1: the light reactions
• stage 2: the dark reactions

Question 3

what are the key components of the light reactions?

Answer 3

• pigments
• photosystems
• electron transport chain

Question 4

what is the role of pigments in photosynthesis?

Answer 4

absorb the light that powers photosynthesis

Question 5

what are the five pigments involved in photosynthesis?

Answer 5

Bacteriochlorophyll a
Chlorophyll a
Chlorophyll b
Phytoerythrobilin
β-carotene

Question 6

chlorophyll a

Answer 6

• 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 7

chlorophyll b

Answer 7

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 8

carotenoids

Answer 8

• 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 9

what are ther three possible fates of energy after being absorbed by pigments?

Answer 9

• 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 10

what is produced during the light reactions?

Answer 10

ATP and NADPH

Question 11

what is produced from photolysis?

Answer 11

4H+ + O2 + 4e-

Question 12

what are the main events of the light reactions?

Answer 12

• The splitting of water molecules (photolysis)
• The production of oxygen
• The excitation and transport of electrons
• The generation of an electrochemical gradient
• The production of NADPH and ATP

Question 13

what is the first stage of the dark (carbgon) reactions?

Answer 13

the Calvin-Benson-Bassam cycle