Almost every high school and college biology textbook I have seen, as well as mo

Question

Almost every high school and college biology textbook I have seen, as well as most college biochemistry and cell biology books, states unequivocally that the product of photosynthesis is glucose. However, it is well known that the end products of photosynthesis are primarily sucrose and starch in most plants (Pereto & Pamblanco 1987; Walker & Sivik 1986). Triose phosphates such as 3-phosphoglyceraldehyde are the main intermediates drained from the Calvin cycle that form these two end products. Starch is the storage carbohydrate synthesized in illuminated chloroplasts and later broken down during metabolism in the dark. Sucrose, a disaccharide, is formed in the green leaf cell cytosol and exported via the phloem, supplying sink areas of the plant with carbon and energy. In these leaf cells, recently formed triose phosphates from the Calvin cycle also exit the chloroplast and enter respiration in the cytosol, providing the carbon skeletons of cell wall components and hundreds of other compounds forming the plant. These triose phosphates and the breakdown products of starch and sucrose also supply carbon and energy to glycolysis and aerobic respiration linking photosynthesis to light-independent metabolism in plant cells (see Salisbury & Ross 1985; Jenson & Sefter 1987; Foyer 1984). To underscore the point, very little if any free glucose seems to form in photosynthetic cells or is carried in the translocatory stream of plants. If for pedagogical reasons, one wishes to identify the products from a metabolic cycle, then triose phosphates are best considered as the net products, and sucrose and starch are the end products, of the Calvin cycle of photosynthesis. Every effort should be made to remove references to glucose from discussions of photosynthesis.

The primary product(s) of photosynthesis is (are):

Explanation / Answer

ANSWER
The primary product of photosynthesis is: b. Glucose
This is given by the equation of Photosynthesis, which is 6CO2 + 6H2O + light energy = C6H12O6 + 6O2

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