Photosynthesis Flashcards
What are the products of photosynthesis?
glucose, H2O, O2
What are the reactants in photosynthesis?
sunlight, CO2, water
Where in the leaf does photosynthesis occur? Where within that?
Mesophyll –> chloroplasts
What are the two main parts of photosynthesis?
Photosystems I and II and the Calvin cycle
What are the reactants for photosystems I and II?
H2O and sunlightW
What are the products for photosystems I and II?
O2, ATP, NADPH
Which of the products of photosystems I and II remain in the chloroplast and which leave?
ATP and NADPH stay, O2 leaves
What are the reactants for the Calvin cycle?
ATP, NADPH, CO2
What is the main product of the Calvin cycle?
sugar
Why does the rate of photosynthesis increase with increased light but then level off?
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)
How can a photosynthetic rate be negative?
Plants consume O2 during cellular respiration
Is the rate of the photosynthesis curve consistent throughout species? When is it not?
Yes, all healthy species not under stress have the same slope
Name 8 factors that influence photosynthesis
Light
[CO2]
Temperature
Growth conditions
Nitrogen availability
Water availability
Leaf thickness
Number of stomata
Explain how each of the 8 factors influence photosynthesis
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
What is carbon fixation?
When C from the atmosphere is converted into an organic compound
What is rubisco? What is its job and what part of photosynthesis is it involved in?
An enzyme that catalyzes carbon fixation. First step of the Calvin cycle
What is photorespiration?
A wasteful pathway that competes with the Calvin cycle –> uses ATP and makes useless molecules and releases CO2 again
What is the problem with rubisco?
Can do either photosynthesis (good) or photorespiration (bad) because it can do the same process with CO2 or O2
What is C3 photosynthesis?
The regular kind that makes a 3 carbon long product in the first step of the Calvin cycle
What is C4 photosynthesis?
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)
Where does carbon fixation happen in C4 plants?
In the mesophyll
Where do steps 2 and 3 (out of 3) happen in C4 plants?
In bundle-sheath cells
What is the benefit of C4 photosynthesis? What is the drawback?
Benefit: reduces the amount of photorespiration
Drawback: uses more ATP
What is CAM photosynthesis?
Carbon fixation and the rest of the Calvin cycle are separated by time
–> fixation at night and Calvin cycle in the day
Why do plants to CAM photosynthesis?
It’s more efficient water usage –> opening stomata at night decreases water loss.
