Photosynthesis is a complex process of synthesis of organic food materials. It is a oxidation - reduction process. Here water is oxidised and carbon dioxide is reduced to carbohydrates. Photosynthesis takes place in two steps: i) light reaction ii) dark reaction
Light Reaction is the first stage in photosynthesis where water is broken in the chlorophyll molecule into H+ ions and OH- ions in the presence of light resulting in the formation of assimilatory powers such as NADPH2 and ATP . It occurs in the grana of chloroplast.

Dark Reaction is the second step in the mechanism of photosynthesis. The chemical processes of photosynthesis occurring independent of light is called dark reaction. It takes place in the stroma of the chloroplast. The Dark reaction of photosynthesis is purely enzymatic and it is slower than the light reaction. In dark reactions, two types of cyclic reaction occur. They are Calvin cycle or C3 Cycle and Hatch Slack Cycle or C4 cycle.
In dark reaction, sugars are synthesised from CO2. The energy poor carbon dioxide is fixed to energy rich carbohydrates using the energy rich compound ATP and the assimilatory power NADPH2 of light reaction. This process is called carbon fixation.
Blackman first demonstrated the existence of dark reaction .Hence it is known as Blackman’s reaction.
Light Reaction vs Dark Reaction
Light Reaction
|
Dark Reaction
|
Occurs : Grana of the chloroplasts. | Occurs: Stroma of the chloroplast |
It is a light dependent process Involves two photosystems: PS I and PS II | This process does not require light. No photosystem is required. |
Photolysis of water takes place and oxygen is liberated. | Photolysis of water does not take place. Carbon dioxide is absorbed. |
ATP and NADPH is produced and they are used to drive the dark reaction. | Glucose is produced. Reduced NADP is oxidised. |
41 comments:
very very helpful
i need something more
gay
Comparing is where?
Thanks you! :)
Pretty helpful, thanks alot.
all backwards
Nyco
blackman's reaction...lol
greatly helpful. direct answers, no need to search for more!!!!!!!!!!!!!!!!!!!!!!
Thanks ! Was so helpful !! :D
Very useful for my project!
-ABHIJITH.D
Really very helpful.
Thanks A Ton. ��
Helpful
Thanks a lot. My students learnt from this. Made my lesson easy.
It's Fucking Awsome Yeeeaaaah!!!!!!!!!!!!!
it was really helpful..keep it up,thumbs up!
It was very helpful to me. Thank you. :)
please explain what light and dark reaction are
Hopefully this will help me in my exam
Why?
thx
It was good.woieeyowie
Thnks a lot ..... . . but fr unknowns u shud explain wid details
great....thanks
good
thank you
I was unknown too.but it is pretty good for me.thanx alot.
thank you
Not bad......it helped....
get lost
nope
It is very useful information about dark and light
Thnxx... Helped a lot
Thnxx.....
too vague
Nice and to the point . thanks
It made me do my exam well, biology exam
Thank you so much it's very my helpful
- vaishu 😍😍😍
thanks better than the other sites i checked
lol...thanx
Post a Comment
We Love to hear from U :) Leave us a Comment to improve this site
Thanks for Visiting.....