11- photosynthesis

Question 1

What are the stages of the light dependent reaction? (6)

Answer 1

1- chlorophyll absorbs light energy
2- this excites electrons (leading to photoionisation)
3- electrons move down ETC via series of redox reactions, causing energy to be given off
4- This energy:
- joins ADP+ Pi > ATP (photophosphorylation)
-photolysis of water > protons (H+) & O2 & e-
- NADP reduced by e- & protons to form NADPH
- chemiomosis

Question 2

What are the products of the light dependent reaction?

Answer 2

ATP, NADPH, O2 (waste)

Question 3

What are the stages of the light independent reaction? (4)

Answer 3

1- CO2 combines with RuBP
2- This forms 2x GP (3C each)
^ This reaction is catalysed by enzyme rubisco
3- GP Reduced to TP, (using ATP, & NADPH, from LDR)
4- TP converted to glucose or used to regenerate RuBP

Question 4

What are the limiting factors of photosynthesis? (3)

Answer 4

1- temperature
2- light intensity
3- CO2 conc

Question 5

Limiting factors- Temperature

Answer 5

• increase in kinetic energy means more E-S complexes

- when reaches optimum temperature, enzymes denature so less E-S complexes

Question 6

Limiting factors- Light intensity

Answer 6

• more light energy absorbed so more LDR occurs so more products for LIDR
• more LIDR occurs so more sugars and more plant growth
• LDR cannot occur without sufficient light

Question 7

Limiting factors- CO2 conc

If low:

Answer 7

• less CO2 combines RuBP so less GP so less reduced to TP so less TP converted to glucose & less converted to RuBP

Question 8

How do you decrease limiting factors in greenhouses? (3)

Answer 8

• introduce artificial light
• have heating
• burn fuel (for more CO2)

Question 9

What is the benefit of minimal limiting factors?

Answer 9

rate of photosynthesis will increase so:

• faster production of glucose allowing for faster respiration
• more ATP for energy for growth
• higher yield

Question 10

Chemiosmotic theory (4)

Answer 10

1- energy is used to AT protons across C membrane
2- This creates electrochemical gradient
3- Protons move via FD down the electrochemical gradient, through ATP synthase channels
4- This catalyses the reaction of ADP+Pi > ATP

Question 11

Which part of the photosynthesis equation is MADE in LDR?

Answer 11

6O2

Question 12

which part of the photosynthesis equation is USED in LDR?

Answer 12

6H2O