Photosynthesis

Envelope membrane

Oil droplets

stroma= cytoplasm 

starch grain

Thylakoid = lemmela and grana

DNA

1- Light dependent stage 

• Takes place in the grana 
• Uses light energy to split water in photolysis, oxygen released as waste product
• Makes ATP and Reduced NADP

2- Light independent stage 

• Takes place in stroma
• Uses the ATP and NADP from the light dependent stage
• Uses carbon dioxide 
• Produces organic molecules such as sugars 

• Light energy absorbed by pigments in the ligh harvesting antennae, this energy is then funneled towards the central core (PHOTOSYSTEM II)
• Electrons in the chlorophyll of PHOTOSYSTEM II  are excited by the energy so the chlorophyll oxidises and loses the electrons.
• These excited electrons have more energy potential so are passed to a series of carriers wehich make up an electron transfer chain. -                                                                     This is used to generate ATP by PHOTOPHOSPHORYLATION
• Photophosphorylation occurs as the energy from the electrons down the chain creating an electrochemical gradient which pumps protons into the grana, which powers ATP synthase.
• As the electrons give energy away they move down the electron transfer chain to PHOTOSYSTEM I.
• Light energy from the harvesting antennae is given to PSI. So the electrons then become excited again and combine with the H+ from photolysis of water to reduce NADP
• As the chlorophyll is now oxidised they replace the lost electrons by splitlling water by photolysis. The electron is then used to reduce chlorophyll in PHOTOSYSTEM II
• Oxygen is created as a waste product of photolysis and is excreted fromt the plant water is also produced.

Carboxylation -

• RuBP combines with carbon dioxide to form 2 x 3 carbon sugar GP ( glycerate phospate) this is helped by the enzyme rubisco.

Reduction

• ATP releases a phosphate group by hydrolysis providing activation energy which is used to oxidise reduced NADP forming NADP, GP is reduced and converted into another triose sugar.

Regeneration

• The triose sugar is then converted back to RUBP through many stages. WHich requires the triose sugars to be phosphorylated by ATP. 

1 turn of the cycle forms 1 carbon = glucose requires 6 turns of the cycle in order to be produced 

A series of reactiions occuring in a cell where the product of one reaction becomes the substrate for the next reaction. 

They can be either anabolic where they build up molecules (photosynthesis) or catabolic where they break down molecules (respiration)  

• Leaf has a large surface area to maximise absorption of light.
• Waxy cuticle on upper and lower surfaces to reduce water loss 
• Stoma on lower part of leaf for efficient gas exchange, loss of water vapour creates the transpiration stream which pulls up minerals from the soil 
• Palisade mesophyll cells are elongated and contain most of the chloroplasts this is where most of photosythesis occurs.
• Spongy mesophyll has large air spaces for the rapid diffusion of gases in and out of the cell
• Xylem carries minerals and water while supporting the plant 
• Phloem carries away the products of photosynthesis mainly sucrose to the rest of the plant