1. Photosynthesis HL

2. 8.2.1 Draw and Label the structure of a chloroplast

3. PHOTOSYSTEM HARVESTS LIGHT ENERGY
Chlorophyll is located in thylakoid membranes and is arranged in groups of hundred of molecules, called photosystems. There are 2 types of photosystem –photosystem I and II. Chlorophyll absorbs light and the energy from the light raises an electron in the chlorophyll molecule to a higher energy level. The electron at a higher energy level is an excited electron and the chlorophyll is photoactivated. Excited electrons from absorption of photons of light anywhere in the photosystem are passed from molecule to molecule until they reach a special chlorophyll molecule at the reaction centre of the photosystem. This chlorophyll passes the excited electron to a chain of electron carriers.

4. CYCLIC PHOSPHORILATION
Involves Photosystem I only.
Sometimes the supply of NADP+ runs out.
When this happen, the electrons return to the electron transport chain that links the two photosystems, rather than being passed to NADP+
As the electrons flow back along the electron transport chain to Photosystem I, they cause pumping of protons, which allows ATP production.

5. NON-CYCLIC PHOSPHORILATION: Z-SCHEME
Photosystem II absorbs light energy and passes on to a chlorophyll molecule P680, at the reaction centre.
The chlorophylls at the reaction centre have the special property of being able to donate excited electrons to an electron acceptor called Plastoquinone.
Plastoquinone collects two excited electrons from Photosystem II and then passes the electrons along a chain of electron carriers to the Photosystem I.
The energy released from the electrons is used to make ATP from ADP +Pi.
Photosystem I absorbs light energy and passes on to a chlorophyll molecule P700, at the reaction centre. It emits two electrons.
These electrons rise to a higher energy level and are picked up by a second electron acceptor.
Since both chlorophylls (P680 and P 700) have now lost electrons, they will both be positive and unstable.
The 2 electrons released from Photosystem II go to replace the two that have been lost by Photosystem I.
P680 of Photosystem II receives its replacement electrons from the splitting of water (photolysis)
During photolysis, the water molecule dissociates into electrons, hydrogens ions and Oxygen.
As we have said, electrons go to Photosystem I.
The oxygen is released as a waste gas.
Hydrogen ions combine with electrons held by the second electron acceptor to give NADPH and also contribute to the electrochemical gradient.

6. LIGHT DEPENDENT REACTION: Photophosphorilation and chemiosmosis
The passage of electrons through the electron transport chain provides the energy to pump hydrogen ions from the stroma to the tylakoid interior.
This set up an electrochemical and concentration gradient, since there are more hydrogen ions inside the tylakoid space than there are outside in the stroma.
Protons (H+)diffuse across the membrane down their conccentration gradient driving synthesis of ATP from ADP + Pi

7. Light Independent Reaction: Calvin Cycle
The fixation of Carbon Dioxide is a light-independent process in which carbon dioxide combines with a five-carbon sugar, Ribulose Bisphosphate (RuBP), to give two molecules of a three-carbon compound, glycerate-3-phosphate.
glycerate-3-phosphate in the presence pf ATP and NADPH from the light dependent stage is reduced to triose phosphate.
This is the point at which carbohydrates is produced in photosynthesis. Some of these triose phosphate condense to form hexose phosphate, sucrose, starch and cellulose or are used to make aminoacids and lipids. Others regenerate RuBP.
The enzyme Ribulose Bisphosphate Carboxylase (RuBISCO) catalyses the combination of Carbon dioxide and RuBP.

8. PHOTOSYNTHESIS: Light Dependent and Independent Reaction

9. Team analogy for the limiting factors theory
Team analogy for the limiting factors theory. Time to vote off the weakest link.

10. Explain the effects of limiting each of the three factors on the process of photosynthesis. It’s not enough to just say “it slows down.”

11. What are the conditions of each of these trials?
Rate of photosynthesis
This graph suggests that CO2 is more important than temperature. Why?
Light intensity