Dark rxn???

[RCLEE]

I read a couple of books and they are contradicting to one another. So if this short of question come up in the DAT, what answer should one choose?

Dark rxn is the carbon fixation in plants that requires ATP and NADPH.

One source states that the dark rxn can occur at night.
(I understand that as long as there's NADPH and ATP, plants can carry out the dark fxn and fix carbon; however, plants don't produce ATP and NADPH like during the day from Photosystem I and II. So plants breaks down glucose made during the day to get ATP and NADPH to fix carbon in the dark rxn that actually would require a lot more energy that's already stored? This does not make sense.)

Another source states that the dark rxn cannot occur at night.

Another asked whether the dark rxn can occur without light T/F. Were there a lot of ambiguous questions in your DAT exam that says without light (but not saying during day or night?

My answers:
The dark rxn would not proceed at night.
The dark rxn can proceed without light (T)

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[wall1two]

I like your questioning of your sources

From what I understand the dark reaction can occur at night but by at night they don't mean all-night. carbon fixation can occur for a brief amount of time due to the realitve surplus of reduced coenzymes (nadph)and ATP that are available in the stroma. ( I'm not sure if it goes for plants too but I read somewhere that ATP is usually used within a second or two of its creation) I assume the nadph is more stable. So basically yeah it can occur at night but for like the first few minutes of night. The term "dark reaction" just means it is cytocrome independent so if you put the Calvin enzymes in a pool of ATP and nadph they could continue in the dark. I'm gonna hit wiki and make sure I'm right but as for now , it can happen at night but briefly and dark just means doesn't use cytochromes ( why didn't I just type that in the first place)

 

[invictusx]

I like your questioning of your sources

From what I understand the dark reaction can occur at night but by at night they don't mean all-night. carbon fixation can occur for a brief amount of time due to the realitve surplus of reduced coenzymes (nadph)and ATP that are available in the stroma. ( I'm not sure if it goes for plants too but I read somewhere that ATP is usually used within a second or two of its creation) I assume the nadph is more stable. So basically yeah it can occur at night but for like the first few minutes of night. The term "dark reaction" just means it is cytocrome independent so if you put the Calvin enzymes in a pool of ATP and nadph they could continue in the dark. I'm gonna hit wiki and make sure I'm right but as for now , it can happen at night but briefly and dark just means doesn't use cytochromes ( why didn't I just type that in the first place)

Dark reactions can occur given the substrates needed to produce ATP. Of course plants won't completely work in night. It's similar to human beings--we can never be producing just insulin or glucagon at one time. They're both simultaneously being produced, depending on the body's need.