USE OF ATP AND NADPH
● The `color{violet}"products of light reaction"` are `ATP,` `NADPH` and `O_2`.
● Of these `O_2` `color{violet}"diffuses out"` of the chloroplast while `color{violet}"ATP and NADPH"` are used to drive the processes leading to the `color{violet}"synthesis of food"`, more accurately, `color{violet}"sugars"`.
● This is the `color{Brown}"biosynthetic phase"` of photosynthesis.
● This process does `color{violet}"not directly depend"` on the `color{violet}"presence of light"` but is dependent on the `color{violet}"products of the"` `color{violet}"light reaction"`, i.e., `ATP` and `NADPH`, besides `CO_2` and `H_2O`.
● This could be verified as immediately after `color{violet}"light becomes unavailable"`, the biosynthetic process continues for
some time, and then stops. If then, `color{violet}"light is made available,"` the synthesis starts again.
.
● We saw earlier that `CO_2` is combined with `H_2O` to produce (`CH_2O`)n or `color{violet}"sugars"`.
● It was of `color{violet}"interest to scientists"` to find out how this reaction proceeded, or rather what was the `color{violet}"first product formed"` when `CO_2` is taken into a `color{violet}"reaction or fixed"`.
● Just after `color{violet}"world war II"`, among the several efforts to put `color{violet}"radioisotopes to beneficial use"`, the work of `color{Brown}"Melvin Calvin"` is exemplary.
● The use of `color{violet}"radioactive"` `C^14` by him in `color{violet}"algal photosynthesis"` studies led to the discovery that the first `CO_2` fixation product was a `color{violet}"3-carbon organic acid."`
● He also contributed to working out the `color{violet}"complete biosynthetic"` pathway; hence it was called `color{Brown}"Calvin cycle"` after him.
● The first product identified was `color{violet}"3-phosphoglyceric acid"`or in short `color{violet}"PGA"`.
● Scientists also tried to know whether `color{violet}"all plants have PGA"` as the first product of `CO_2` `color{violet}"fixation"`, or whether any `color{violet}"other product"` was formed in other plants.
● Experiments conducted over a `color{violet}"wide range of plants"` led to the discovery of `color{violet}"another group of plants,"` where the `color{violet}"first stable product"` of `CO_2` fixation was again an `color{violet}"organic acid"`, but one which had `color{violet}"4 carbon atoms"` in it.
● This acid was identified to be `color{violet}"oxaloacetic acid or OAA"`.
● Since then `CO_2` `color{violet}"assimilation during photosynthesis"` was said to be of `color{violet}"two main types"`: those plants in which the `color{violet}"first product"` of `CO_2` fixation is a `C_3` acid `color{Brown}"(PGA"`), i.e., the `C_3` pathway, and those in which the first product was a `C_4` acid (`color{Brown}"OAA"`), i.e., the `C_4` pathway.
● Of these `O_2` `color{violet}"diffuses out"` of the chloroplast while `color{violet}"ATP and NADPH"` are used to drive the processes leading to the `color{violet}"synthesis of food"`, more accurately, `color{violet}"sugars"`.
● This is the `color{Brown}"biosynthetic phase"` of photosynthesis.
● This process does `color{violet}"not directly depend"` on the `color{violet}"presence of light"` but is dependent on the `color{violet}"products of the"` `color{violet}"light reaction"`, i.e., `ATP` and `NADPH`, besides `CO_2` and `H_2O`.
● This could be verified as immediately after `color{violet}"light becomes unavailable"`, the biosynthetic process continues for
some time, and then stops. If then, `color{violet}"light is made available,"` the synthesis starts again.
.
● We saw earlier that `CO_2` is combined with `H_2O` to produce (`CH_2O`)n or `color{violet}"sugars"`.
● It was of `color{violet}"interest to scientists"` to find out how this reaction proceeded, or rather what was the `color{violet}"first product formed"` when `CO_2` is taken into a `color{violet}"reaction or fixed"`.
● Just after `color{violet}"world war II"`, among the several efforts to put `color{violet}"radioisotopes to beneficial use"`, the work of `color{Brown}"Melvin Calvin"` is exemplary.
● The use of `color{violet}"radioactive"` `C^14` by him in `color{violet}"algal photosynthesis"` studies led to the discovery that the first `CO_2` fixation product was a `color{violet}"3-carbon organic acid."`
● He also contributed to working out the `color{violet}"complete biosynthetic"` pathway; hence it was called `color{Brown}"Calvin cycle"` after him.
● The first product identified was `color{violet}"3-phosphoglyceric acid"`or in short `color{violet}"PGA"`.
● Scientists also tried to know whether `color{violet}"all plants have PGA"` as the first product of `CO_2` `color{violet}"fixation"`, or whether any `color{violet}"other product"` was formed in other plants.
● Experiments conducted over a `color{violet}"wide range of plants"` led to the discovery of `color{violet}"another group of plants,"` where the `color{violet}"first stable product"` of `CO_2` fixation was again an `color{violet}"organic acid"`, but one which had `color{violet}"4 carbon atoms"` in it.
● This acid was identified to be `color{violet}"oxaloacetic acid or OAA"`.
● Since then `CO_2` `color{violet}"assimilation during photosynthesis"` was said to be of `color{violet}"two main types"`: those plants in which the `color{violet}"first product"` of `CO_2` fixation is a `C_3` acid `color{Brown}"(PGA"`), i.e., the `C_3` pathway, and those in which the first product was a `C_4` acid (`color{Brown}"OAA"`), i.e., the `C_4` pathway.
