Photosynthesis

Question 1

Describe The Photolysis of water during the Light-dependant reaction of photosynthesis.

Answer 1

The Photolysis of Water -
- light energy is absorbed by the chlorophyll, splitting water into hydrogen ions, electrons and oxygen molecules.
- the hydrogen ions are picked up by NADP to form NADPH for the light-independent reaction.
- the electrons replace those lost during the photoionisation of chlorophyll.
- the oxygen is either used for respiration, or diffuses out of the leaf during the stomata.

Question 2

Describe The Photoionisation of Chlorophyll during the light-dependant reaction of photosynthesis.

Answer 2

• light energy from the sun is absorbed by the chlorophyll, resulting in the electrons present in the chlorophyll gaining energy, so raising them up an energy level, causing them to leave the chlorophyll - photoionisation.

Question 3

Describe the process of Chemiosmosis during the light-dependant reaction.

Answer 3

• the electrons that gained energy and were released from the chlorophyll move along a series of electron carrier proteins in the thylakoid membrane of the mitochondria.
• as the electrons move along the proteins, they release energy, so losing energy, and some of that energy is used to pump the protons formed during the photolysis of water from the stroma, across a proton pump and into the thylakoid lumen.
• their results in an electrochemical gradient being built up, which allows the protons to move again, by facilitated diffusion,, back down their concentration gradient, through ATP synthase back to the stroma.
• as the proton attaches to and moves through then enzyme, with which the shape change of the enzyme catalyses the phosphorylation of ADP into ATP.
• reduced NADP is formed when the protons are back on the stroma side, and the NADP picks up the electrons at the end of the electron transport chain, as well as the protons once they’ve passed through the ATP synthase, which reduces the NADP forming NADPH.

Question 4

Describe the process of the Calvin cycle in the light-independent reaction.

Answer 4

• RuBP reacts with CO2 (catalysed by rubisco) to form 2 molecules of GP.
• GP is then formed into TP using the energy from the deformation of ATP into ADP + Pi
  finish