Photosynthesis

Question 1

Site of Light Dependent Reaction

Answer 1

Thylakoids of the chloroplast

Question 2

Photoionisation

Answer 2

Chlorophyll absorbs light energy from photons of light causing two electrons to be excited and leave the chlorophyll, which is now ionised.

Question 3

Electron Transfer Chain

Answer 3

The electrons lost by the chlorophyll reduce an electron carrier in the thylakoid membrane. The electrons pass along a series of electron carriers through a series of oxidation-reduction reactions releasing energy. NADP acts as terminal electron acceptor and is reduced to reduced NADP using H+ ions

Question 4

Chemiosmosis

Answer 4

Energy released from the ETC is used to actively transport H+ ions from the stroma into the thylakoid space. High conc of H+ ions in the thylakoid space, low conc in the stroma, H+ ions diffuse into stroma through ATP synthase, a stalked particle, ATP is formed from ADP and a phosphate ion.

Question 5

Photolysis of Water

Answer 5

Energy from photons of light split water molecules.
2H2O => 4H+ + 4e- + O2
H+ ions: move through ATP synthase and reduce NADP forming reduced NADP
Electrons: replace electrons lost by chlorophyll
O2: respiration or waste

Question 6

Products of Light Dependent Reaction

Answer 6

ATP
NADP + 2H+ +2e- => reduced NADP (catalysed by dehydrogenase enzymes)

Question 7

Site of Light Independent Reaction

Answer 7

Stroma of the chloroplasts

Question 8

Calvin Cycle: Carbon Fixation

Answer 8

RuBP (5C) + CO2 => unstable 6C => 2 GP (3C)
catalysed by rubisco

Question 9

Calvin Cycle: Reduction

Answer 9

2 GP reduced to 2 TP (3C) using 2 reduced NADP which is oxidised to 2 NADP and 2 ATP which is hydrolysed to 2 ADP and 2 phosphate ions.

Question 10

Calvin Cycle: Production of Useful Organic Products

Answer 10

1C leaves the cycle after the formation of 2 TP and is used to produce useful organic products

Question 11

Calvin Cycle: Regeneration

Answer 11

After 1C leaves for production organic products, the remaining 5C are converted into RuBP using an ATP molecule which is hydrolysed to ADP and a phosphate ion.

Question 12

Chloroplast Adaptations

Answer 12

Contains both DNA and ribosomes to make proteins such as the enzyme rubisco needed for photosynthesis.
Large surface area of thylakoid membrane for ETC

Question 13

Limiting Factors

Answer 13

Light intensity (light compensation point: when there is no net exchange of gases as CO2 taken up for photosynthesis is equal to CO2 produced by respiration and vv for O2)
Temperature
CO2 levels
(Magnesium levels for chlorophyll)