Photosynthesis Flashcards
Where do the light dependent and light independent reactions occur in plants?
light-dependent - in the thylakloid of chloroplasts.
Light-independent - in the stroma of chloroplasts
Explain the role of light in photoionisation.
Chlorophyll molecues absorb energy form photons of light.
This excites ‘2 electrons’ which raises them to a higher energy level, cuasing them to be released from the chlorophyll.
What happens in the electron transfer chain?
Electrons released from chlorophyll move down a series of carrier proteins embedded in the thylakoid memrane and under a series of redox reactions which release enegry.
How is a proton concentration gradient estbalished in chemiosmosis?
Some energy released in the electron transfer chain is coupled to the active transport of H+ ions from the stroma into the thylakoid space
How does chemiosmosis produce ATP in the light dependent stage?
H+ ions move down the concnetration gradient form the stroma into the thylakoid space via the transmembrane channel protein ATP synthase. ATP synthase catalyses the conversion of ADP and inorganic phospahte into ATP.
Describe non-cyclic photophosphorylation
Uses photosystmes 1 and 2. Excited electrons enter electron transfer chain to produce ATP. NADP acts as a final electron acceptor and is reduced. Photolysis of water occurs to release electrons to replace the ones lost in photosystem 2.
Describe cyclic photophosphorylation.
Uses only photosystem 1. Excited electrons enter electron transfer chain to produce ATP then return directly to photosystem.
- no reduction of NADP
- no photolysis of water
State the purpose of cyclic and non cylic photophosphorylation.
non- cyclic - produces additional ATP to meet surplus energy demands of cell.
cyclic - produces ATP and reduced NADP for calvin cycle to produce biological compounds..
How does ATP provide energy for metbolic reactions?
Hydrolysis of high energy bond between ADP and Pi releases small amount of energy that can be directly coupled to a reaction with little energy wasted as heat.
What is the equation for the photolysis of water?
2H20 produces 4H+ + 4e- + O2
Describe the light independent reaction.
Carbon dioxide combines with RUBP. It produces two GP using enzyme RUBISCO. Gp reduced to triose phosphate (GALP) using reduced NADP usig energy from ATP. GALP converted to glucose RUBP.
How does the structure of a chloroplast maximise the rate of the light dependent reaction?
- ATP synthase channels between granal membrane
- Large surface area of thylakoid membrane for eletcron transfer chain
- Photosystems position chloropyll to enable maximum absorption of light.
How does the structure of a chloroplast maximise the rate of the light independent reaction?
- Own DNA and ribosomes for proteins synthesis of enzymes
- Concentration of enzymes and subtrates in stroma is high
