Photosynthesis
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What is the first stage of photosynthesis
Light dependent reaction
Second stage of photosynthesis
Light independent reaction For this to take place two products of the light dependent reaction are required nadph and atp
Where does the light dependant reaction take place
In the thylakoids membrane. It requires an enzyme in this membrane that catalyses production of atp
Producing atp
Enzyme in thylakoid membrane called atp synthase combines adp with pi This requires energy which is provided by H+ions / protons
How do protons provide energy for ATP synthase
Higher conc of H+ ions in the thylakoid space than the stroma creating a proton gradient. Protons diffuse down gradient through atp synthase. This is called chemiosmosis. This chemiosmosis provides energy for atp ssynthase to catalyse
What is the movement of ions across a partially permeable membrane down a conc gradient called
Chemiosmosis
What is photophosphorylation
Chemiosmosis providing energy to atp synthase to catalyse the phosphorylation of adp to atp
Maintaining the proton conc gradient
To maintain the proton gradient, there is active transport of protons from the stroma to the thylakoid space. This ensures there is a higher concentration of protons in the thylakoid space compared to the stroma Energy is supplied by electrons provided by chorophyll
What happens when light energy hits chlorophyll
Chlorophyll absorbs the light. The light is transferred to two electrons within chlorophyll. Electrons gain energy and becomee excited and they propel out the chlorophyll. Its lost electron so is oxidised and positively charged
What is it called when light energy causes chlorophyll to lose two electrons
Photoionisation
What happens after the electrons have left the chlorophyll after photoionisation
Electron transfer chain as electrosn pass though multiple proton complex. Due to a series of oxidation and reduction reactions. These reactions release energy which are transferred to a protein complex enabling it to actively transport protons.
What happens when electrons reach the final protein in electron transfer chain
Nadp reacts with these electrons and a H+ ion that hasnt been reacted with in the stroma. So nadp becomes reduced
How are electrons repeatidly reformed in chorophyll
Electrons are replaced by water. Light hitting chlorophyll splits water up into 2e-+2H+ 1/2O2 Electorns formed in this reaction move into chlorphyll.
What is photolysis
When lighte energy splits water into protons electrons and oxygen Electrons help in electron transfer chain and protons help maintain gradient and oxygen used in repiration or moved out of plant
Hwo are chlorplasts adapted for photosynthesis
• Thylakoid membrane have a large sa. Maximising ammount tof atp and nadph that can be made at one time • Proteins hold chlorphyl in a way where light can be absorbed maxium amount • Thylakoid membrane contain atp synthase for atp. Also selectively permeable which maintains proton gradient • Chloroplasts contai =n both dna and ribosomes. Meaning proteins involved in light dependent raction can be quickly produced
Where does the light independant reaction take place
In the stroma
What are 3 moleules created in light independent reaction
When co2 enters the stroma…
It reacts with a molecule called ribulose biphosphate (RuBP) which is a 5c and 2 phosphate. Catalysed by enzyme called rubisco They react together to form 2xGP (3c and 1 phosphate)
How does gp turn into triosephosphate
Gp Needs to lose oxygen and gain hydrogen. So is reduced. Reduced nadp suplies the hydorgen for this reaction.
What provides energy for thed reduction of gp to triosephosphate
Atp breaking down into adp and pi
What are the organic substances produced by triose phosphate
Glucose - used for respiration Amino acids - used to make proteins Triglycerides - energy storage And more rubulose bisphosphate so ldr can continue (requires atp)
What factors limit photosynthesis
Light co2 and temp
Describe how light dependent reaction results in the production of ATP
Light energy is absorbed by the photosystem exciting electrons out of the chlorophyll. Next the electrons move through electron transport chain releasing energy. This energy is used to create a proton gradient between the thylkaoid space and the stroma. Protons diffuse back into the stroma via chemiosmosis. This provides energy for atp synthase to catalyse the reaction of adp and pi to form atp. Called photophoshorylation
Describe the role of water in light dependent reaction
In the light dependent reaction, water undergoes photolysis. The electrons replace those lost from chlorophyll during photoionisation. While protons maintain a high proton concentration in the thylakoid space. And are picked up by nadp/ used in redcution. Oxygen also diffuses out plant in respiratiom