Photosynthesis

Question 1

Where does photosynthesis take place?

Answer 1

Occurs in the leaf, in the chloroplasts

Question 2

What is the equation for photosynthesis?

Answer 2

6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

Question 3

What is the granum?

Answer 3

A stack of about 100 thylakoids in the chloroplast

Question 4

What is a thylakoid

Answer 4

A flat disk like structure

Question 5

What is the stroma?

Answer 5

The fluid filled matrix of the chloroplast

Question 6

Where does the light-dependent stage of photosynthesis take place?

Answer 6

In the membrane of the thylakoid

Question 7

What is the purpose of the light-dependent stage?

Answer 7

To synthesise ATP

Question 8

Which photosystem occurs first?

Answer 8

Photosystem 2

Question 9

What is the name of the pigment found in photosystem 2?

Answer 9

P680

Question 10

What is photoionisation?

Answer 10

Where light provides high energy to 2 electrons in a pigment so that they can be released

Question 11

What accepts electrons in an electron transport chain?

Answer 11

Electron acceptors

Question 12

What is ATP made from?

Answer 12

ADP + Pi

Question 13

Where is ATP used after the LDR?

Answer 13

The Calvin Cycle

Question 14

What is the difference between cyclic and non-cyclic photophosphorylation?

Answer 14

• Cyclic only occurs at photosystem 2
• After passing through the electron acceptor, they return to the chlorophyll they came from.
• Non-cyclic produces more ATP

Question 15

What is the purpose of the light-independent reaction?

Answer 15

To synthesise useful organic molecules

Question 16

Where does the carbon dioxide in the Calvin cycle come from?

Answer 16

The atmosphere. It diffuses into the leaf and through the membranes to get to the stroma

Question 17

What is the name of the enzyme involved in the Calvin Cycle?

Answer 17

Rubisco

Question 18

What reaction does rubisco catalyse?

Answer 18

RuBP + Carbon Dioxide

Question 19

What is the product of the carboxylation of RuBP?

Answer 19

2 molecules of GP

Question 20

Where does NADPH in the calvin cycle come from?

Answer 20

the light dependent reaction

Question 21

What is the role of NADPH in the calvin cycle?

Answer 21

To reduce GP into TP (triose phosphate)

Question 22

Where does NADP go after reducing GP?

Answer 22

To the light dependent reaction to be reduced again

Question 23

What useful organic molecules can TP be converted to?

Answer 23

Starch, cellulose, glucose, amino acids and nucleotides

Question 24

If not converted to an organic molecule, what happens to TP?

Answer 24

Converted into RuBP to start the cycle again

Question 25

If light intensity was dramatically reduced, how would it affect the rate of photosynthesis?

Answer 25

• ATP and NADP levels will fall which will pause the LDR
• Conversion of GP to TP requires ATP, so this will slow the rate of the Calvin cycle
• RuBP levels will fall so there will be an increase of carbon dioxide in the chloroplast
• RATE DECREASES

Question 26

If carbon dioxide levels rose dramatically, how would it affect the rate of photosynthesis?

Answer 26

-More carboxylation will increase levels of RuBP, GP & TP
-Will cause the stomata to open, which will cause water loss and wilting
- Carbon dioxide levels will reduce when the stomata close as a stress response
RATE DECREASES

Question 27

If the temperature rises dramatically, how would if affect the rate of photosynthesis?

Answer 27

• High temps increase kinetic energy of molecules in LIR
• High temps also increase rate of transpiration, causes plants to wilt
• Stress reaction causes stomata to close and this reduces carbon dioxide availability
• Rubisco can denature
  RATE DECREASES

Question 28

Why is it beneficial that stomata are closed at night?

Answer 28

Plants can’t photosynthesise without light, water can be lost when the stomata open, to reduce water loss and maintain cellular water content the stomata will close.