Photosynthesis

Question 1

Describe the cyclic light-dependent reaction

Answer 1

1) light energy excites electrons in photosystem 2 (PSII)
2) these electrons pass down electron transport chain + ATP produced
4) Sun excites electrons from PSI
5) Electrons pass along second ETC; second ATP produced
6) Electeons lost from PSI replaced by electrons excites from PSII

Question 2

Describe the difference in cyclic and non-cyclic phosphorylation

Answer 2

Cyclic —> 2e- from PSI move back to replace PSII, does not produce reduced NADP
Non-cyclic —> light breaks down water, producing 2e-, O2 and H+; H+ used to reduce NADP

Question 3

Where does the calvin cycle take place?

Answer 3

Stroma (as all needed enzymes found here)

Question 4

Describe process of calvin cycle

Answer 4

1) CO2 diffusés info stroma and combines with 5 carbon molecule RuBP (ribulose biphosphate)
2) means carbon is fixed into organic molecule; enzyme Rubisco catalysed reaction to form unstable 6-carbon compound
3) unstable 6-carbon compound broken down into GP (glycerate phosphate)
4) each GP converted to 3-carbon TP (triose phosphate, aka GALP) using energy from ATP and NADPH+ (reduced NADP)
5) RuBP regenerated from TP using ATP

Question 5

How many calvin cycles must occur to create glucose?

Answer 5

• 6 cycles
• produces 12 TPs, 2 removed to make glucose, other 10 recycle to make RuBP
  -10 3-carbon TPs = 30 carbons so makes 6 5-carbon RuBPs

Question 6

How many carbons does RuBP, TP and GP contain?

Answer 6

RuBP = 5
TP = 3
GP = 3

Question 7

Describe non-cyclic phosphorylation

Answer 7

1) light energy excites electrons in photosystem 2 (PSII)
2) these electrons pass down electron transport chain + ATP produced
3) Electrons lost from PSII replaced by photolysis of water
4) Sun excites electrons from PSI
5) Electrons pass along second ETC; second ATP produced
6) Electeons lost from PSI replaced by electrons excites from PSII
7) coenzyme NADP accepts electron w a hydrogen ion to form reduces NADP
8) reduced NADP used in LIR

Question 8

Describe how chloroplast structure relates to its function

Answer 8

-Double membrane
-Stacks of thylakoid membranes called grana, contain pigments such as chlorophyll arranged in photo systems —> site of LDR
-Grana surrounded by fluid called stroma —> contains all needed enzymes for LIR
-Starch granules —> store products of photosynthesis