Photosynthesis and Respiration

Question 1

Overall reaction

Answer 1

6CO2 + 6H2O–> (light) C6H12O6 +6O2

Question 2

Where does light dependent reactions occur

Answer 2

In the thylakoid membrane of chloroplasts

Question 3

What is the light energy captured by

Answer 3

Z-scheme

Question 4

Two photosystems of Z-scheme

Answer 4

1. Photosystem 1 (P700)
Source of NADPH
2. Photosystem ll (P680) 
Source of ATP
*both need sunlight for energy and electron transport chain are involved in both to produce ATP and NADPH

Question 5

inputs for light reactions

Answer 5

ADP, NAD+, H2O, energy

Question 6

outputs for light reactions

Answer 6

ATP, NADPH, O2

Question 7

where does light independent reactions occur

Answer 7

in the stroma of chloroplast

Question 8

three phases of Calvin- Benson Cycle

Answer 8

Fixation of CO2 through reduction and regeneration of CO2 acceptor RuBP

Question 9

First stable product

Answer 9

3C sugar (3-PGA)
C3 cycle or pathway

Question 10

Why is rubisco not efficient

Answer 10

It fixes O and C but when photorespiration happens Rubisco isnt efficient

Question 11

Photorespiration

Answer 11

when Rubisco binds to O2 instead of CO2

• CO2 is produced instead of being fixed
• C3 plants compensate by making lots of rubisco

Question 12

What is the most abundant protein on earth?

Answer 12

RUBISCO

Question 13

List and briefly describe the factors that affect photosynthesis #1

Answer 13

1. Temp
   - effect varies w/species
   > cool-season species 65-80 degrees F
   > Warm-season species 80-95 degrees F
   - rate of photosynthesis increases as temp increases
   > when its too hot, stomata close

Question 14

Factor that affects photosynthesis #2

Answer 14

Water

• drought stress results in stomata closure
• excessive water reduces root absorption

Question 15

Factor that affects photosynthesis #3

Answer 15

Light quality

- most effective at 400-500 nm (blue) and 650-700 nm (red)

Question 16

Factor that affects photosynthesis #4

Answer 16

Light intensity
- light compensation point
> point where CO2 uptake = CO2 released

Question 17

Factor that affects photosynthesis #5

Answer 17

CO2 concentration
- CO2 compensation point
> point where CO2 fixed = CO2 produced by respiration
- C4 plants have a lower CO2 compensation point than C3 plants

Question 18

Leaf area index

Answer 18

Ratio of the surface area to the ground surface area.

Question 19

Leaf are duration

Answer 19

The integration of LAI over time.
- calculated by multiplying avg. LAI by time
> can account for 50% of differences in grain yield

Question 20

What factors affect light interception

Answer 20

leaf inclination
leaf grouping
leaf glossiness
leaf thickness

Question 21

Types of leaf inclination:

Answer 21

Planophile: most leaves are nearly horizontal
Erectophile: most leaves are nearly vertical
Plagiophile: most leaves are inclines 45 degrees from horizntal
Extremophile: Half the leaves are nearly horizontal and half are nearly vertical
Uniform distribution: leaves of all inclinations are present in equal proportions

Question 22

Cellular respiration equation

Answer 22

C6H12O6 + 6O2 –> 6CO2+ 6H2O + 36 ATP

Question 23

How efficient is respiration and what happens to the energy that is not available for plant use>

Answer 23

Efficiency is about 38%; rest of energy is lost as heat

Question 24

What are the three stages of respiration and where does each occur

Answer 24

1. Glycolysis: in cytoplasm
2. Krebs cycle: in matrix of mitochondria
3. Oxidative phosphorylation: electron transport chain; in inner membrane of mitochondria

Question 25

Maintenance respiration

Answer 25

• Used to maintain plant and support its functions
• for replacement/ repair, for uptake of nutrients, for maintenance of osmotic pressure in cells
• amount of energy required for maintenance depends on plant size, age, N content of existing structures, and climate

Question 26

Growth respiration

Answer 26

• energy required for biosynthesis of new plant cell/ tissues
• directly impacts growth and crop yield