Photosynthesis Flashcards
how does does structure relate to the role of a chloroplast?
3.3.5.2
- The thlakoids have a large surface area which allows for a greater amount of light intensity to be absorbed
- Chloroplast contains a nuclear envelope which keeps the reactants for photosynthesis close to the reaction sites
- The stroma conatins enzymes, sugars and organic acids for the light independent reaction
What is the overall equation of photosynthesis? why is light energy required?
3.3.5.3
6CO2+ 6H20 + energy (light) —-> C6H12O6 + 6O2
light energy is required to break the bonds in the water molecule. The free hydrogen bonds then bind with Carbon dioxide to form glucose ( fuel) and the remaining oxygen is a side product
Explain the light dependent reaction - Cylcic phosphorylation
3.3.5.4
- Requires light energy
- takes place in the thylakoid membranes
Cyclic phosphorylation-
- only forms small amount of ATP
- electron is restored back to the photosystem
- only involves one photosystem (PS1)
- Light in the form of photon hits PS1 where it is abosrbed
- causes the electron to be excited and go up energy states
- goes through the electron transport chain to a lower energy state
- energy produced is used to phosphorylate ADP + Pi into ATP
Explain the light dependent stage- non cyclic photophosphorylation
3.3.5.4
- Forms reduced NADP and ATP
- electron is not restored therefore water is broken down by photolysis
- involved PS1 and PS2
- light energy (photons) hits PS2 which causes the electron to go to an increased energy state
- the electron for PS2 is restored by photolysis of water forming the oxygen side product
- electron which is in a high energy state goes through the electron transport chain to a lower energy level
- The electron is taken in by PS1
- The electron in PS1 becomes excited and goes to a higher energy state
- electron goes through an electron transport chain
- This electron and a H+ ion is transferred to NADP to form reduced NADP
How does the energy produced from the electron transport chain produce ATP?
3.3.5.4
The energy released when an electron goes through the transport chain from PS2 to PS1 is used to transport protons into the thlakoid. This causes a proton gradient across the membrane as the thlakoid has a greater concentration than the stroma. The proton moves down the concentration gradient back into the stroma through ATP synthase. The energy provided when H+ goes through the enzyme provides energy to bind ADP + Pi
Why is energy required to form ATP and how is energy released from the breakdown of ATP?
3.3.5.5
ATP is synthesises from ADP + Piusing energy from a energy releasing reaction such as respiration. The energy is stored in the phosphate bond.
When ATP is broken down , chemical energy is realeased from the phosphate bond and used by the cell
ATP synthase catalyses both reaction
explain the light independent reaction- location, conditions and molecules needed
3.3.5.6
- takes place in the stroma
- called the calvin cycle
- calvin cycle must spin six timse to produce one glucose molecule therefore 18 ATP and 12 reduced NADP is required from the light dependent.
explain the light independent reaction- Calvin cycle
- CO2 diffuses into the stroma from the stomata
- combines with RuBP ( 5 carbons) catalysed by Rubisco
- This is an unstable intermediate ( 6 carbons)
- This breaks down into two molecules of GP
- 2x ATP (energy) and 2x reduced NADP ( provides H+) is required to reduce GP into TP (GALP)
- Reduced NADP becomes Oxidised NADP
- GALP is converted into usefeul organic compounds and to regenerate RuBP
- Regenerating RuBP uses a ATP
what are the useful substances formed by GALP
3.3.5.6
forms carbohydrates, lipids proteins and nucleic acids.
- Carbohydrates - simple sugars e.g. glucose formed by two TP joining
- Lipids- made using glycerol, synthesised from TP
- Amino acids- made from GP
- nucleic acids- Sugar group in RNA made from TP
