Photosynthesis

Question 1

What are the products of photosynthesis?

Answer 1

glucose, H2O, O2

Question 2

What are the reactants in photosynthesis?

Answer 2

sunlight, CO2, water

Question 3

Where in the leaf does photosynthesis occur? Where within that?

Answer 3

Mesophyll –> chloroplasts

Question 4

What are the two main parts of photosynthesis?

Answer 4

Photosystems I and II and the Calvin cycle

Question 5

What are the reactants for photosystems I and II?

Answer 5

H2O and sunlightW

Question 6

What are the products for photosystems I and II?

Answer 6

O2, ATP, NADPH

Question 7

Which of the products of photosystems I and II remain in the chloroplast and which leave?

Answer 7

ATP and NADPH stay, O2 leaves

Question 8

What are the reactants for the Calvin cycle?

Answer 8

ATP, NADPH, CO2

Question 9

What is the main product of the Calvin cycle?

Answer 9

sugar

Question 10

Why does the rate of photosynthesis increase with increased light but then level off?

Answer 10

It increases because that is when it is light limited, so more light allows it to photosynthesize more. At some point though, there won’t be enough CO2 or enzymes to keep up with high photosynthesis, so it levels off (Calvin cycle limited)

Question 11

How can a photosynthetic rate be negative?

Answer 11

Plants consume O2 during cellular respiration

Question 12

Is the rate of the photosynthesis curve consistent throughout species? When is it not?

Answer 12

Yes, all healthy species not under stress have the same slope

Question 13

Name 8 factors that influence photosynthesis

Answer 13

Light
[CO2]
Temperature
Growth conditions
Nitrogen availability
Water availability
Leaf thickness
Number of stomata

Question 14

Explain how each of the 8 factors influence photosynthesis

Answer 14

Light we already know
[CO2] : same curve as light, first CO2 limited then light limited
Temperature: too cold makes reactions too slow so rate increases rapidly (enzyme limited) then there’s an optimum before it decreases when it’s too hot bc heat can destroy enzymes (enzyme limited).
Growth conditions: ask about in OH
Nitrogen: involved in rubisco, same shape curve as light
FILL IN THE REST

Question 15

What is carbon fixation?

Answer 15

When C from the atmosphere is converted into an organic compound

Question 16

What is rubisco? What is its job and what part of photosynthesis is it involved in?

Answer 16

An enzyme that catalyzes carbon fixation. First step of the Calvin cycle

Question 17

What is photorespiration?

Answer 17

A wasteful pathway that competes with the Calvin cycle –> uses ATP and makes useless molecules and releases CO2 again

Question 18

What is the problem with rubisco?

Answer 18

Can do either photosynthesis (good) or photorespiration (bad) because it can do the same process with CO2 or O2

Question 19

What is C3 photosynthesis?

Answer 19

The regular kind that makes a 3 carbon long product in the first step of the Calvin cycle

Question 20

What is C4 photosynthesis?

Answer 20

The fancy kind that makes 4 carbon long products during carbon fixation. It takes an extra step that uses ATP and it is separated into two cells: mesophyll (carbon fixation) and bundle-sheath cells (the rest of the Calvin cycle)

Question 21

Where does carbon fixation happen in C4 plants?

Answer 21

In the mesophyll

Question 22

Where do steps 2 and 3 (out of 3) happen in C4 plants?

Answer 22

In bundle-sheath cells

Question 23

What is the benefit of C4 photosynthesis? What is the drawback?

Answer 23

Benefit: reduces the amount of photorespiration

Drawback: uses more ATP

Question 24

What is CAM photosynthesis?

Answer 24

Carbon fixation and the rest of the Calvin cycle are separated by time
–> fixation at night and Calvin cycle in the day

Question 25

Why do plants to CAM photosynthesis?

Answer 25

It’s more efficient water usage –> opening stomata at night decreases water loss.