Chapter 8 Exam 3

Question 1

how are reactive oxygen species generated

Answer 1

when not enough NADP+ is available, high energy electrons will reduce O2 instead of NADP+

Question 2

what do xanthophylls do

Answer 2

convert excess light energy to heat, reducing the rate at which energy and electrons enter the ETC

Question 3

what do antioxidants do

Answer 3

detoxify ROS

Question 4

why are xanthophylls helpful

Answer 4

good strategy in high sunlight because the plant can’t handle all the energy they’re getting

Question 5

what are the 3 steps in the Calvin cycle

Answer 5

1. carboxylation
2. reduction
3. regeneration

Question 6

what happens in carboxylation

Answer 6

the addition of CO2 to RuBP generates (2) 3PGA molecules

Question 7

how many carbons does RuBP contain

Answer 7

5

Question 8

how many carbons does 3PGA have

Answer 8

3

Question 9

what catalyzes carboxylation

Answer 9

rubisco

Question 10

what happens in reduction

Answer 10

NADPH transfers high energy electrons that supercharge 3PGA to make 2 triose phosphates

Question 11

how many carbons do triose phosphates contain

Answer 11

3

Question 12

what happens in regeneration

Answer 12

if you have (5) triose phosphates, they will be rearranged into (3) 5-carbon compounds and regenerated as RuBP

Question 13

what does each CO2 molecule that enters the cycle require

Answer 13

3 ATP and 2 NADPH (1 ATP and 1 NADPH for each 3PGA and one ATP for regeneration)

Question 14

what happens to excess carbohydrates

Answer 14

they are stored in starch granules

Question 15

what is the purpose of starch granules

Answer 15

they provide the plants with energy source at night when there is no light to drive photosynthesis

Question 16

what happens to the Calvin cycle in high light

Answer 16

it can’t use all the NADPH produced, if no NADP+ is returned the high energy electrons damage the cell. the electrons are shunted into a pathway that increases production of ATP and decreased production of NADPH by redirecting electrons from PS1 from Fd back to the cytochrome b6f proton pump

Question 17

what can happen to the Calvin cycle if there is an input of O2 instead of CO2

Answer 17

rubisco adds O2 to RuBP resulting in one molecule of 3PGA and one molecule of 2-phosphoglycolate which can’t be used by the Calvin cycle. this results in a net loss of reduced carbon and fewer carbohydrates exit