If green plant cells are incubated in the presence of CO2 molecules containing radioactive carbon atoms, the fate of the carbon atoms can be followed. In an experiment, radioactive CO2 was given for 1 minute to plant cells, and then the cells were examined after 1, 5, 10, 20, and 30 minutes. The following molecules were labeled with radioactive carbon at some point(s): glucose, glyceralde-hyde 3-phosphate, glycine (an amino acid), 3-phospho-glycerate, ribulose 1,5-bisphosphate, and sucrose. Required:
List these molecules in the order in which they first become labeled.

Explanation:

The glycine, among other amino acids, helps to improve chlorophyll production and promotes the process of photosynthesis.  

Calvin cycle

During the carbon fixation phase, a CO² molecule combinate with a ribulose 1,5-bisphosphate to form 6-carbonated molecules, which will divide into two 3-phosphoglycerate molecules.  

During the reduction phase, NADPH donates its electrons to reduce 3-phosphoglycerate molecules, and turn them into glyceraldehyde 3-phosphate.

During the regeneration phase, a glyceraldehyde 3-phosphate molecule leaves the cycle and goes to the cytosol to form glucose. This step can be done when three CO² enter the cycle and produce six glyceraldehyde 3-phosphate molecules. One of them leaves the cycle to form glucose, while the other five are recycled.

Cytosol:

Once in the cytosol, glyceraldehyde 3-phosphate molecules are used to form glucose and fructose. These two molecules are the monosaccharides that form the sucrose.

Once sucrose is formed, it is transported from the photosynthetic tissues to different parts of the plant by the phloem.  

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