Concerning post fixation synthesis of storage and transport sugars, which is FAL

Question

Concerning post fixation synthesis of storage and transport sugars, which is FALSE?

A. The reimport of the inorganic phosphate into the chloroplast is necessary for the production of NADPH in the light-dependent reactions.

B. Starch is synthesized in the chloroplast as a major store of sugar for later use. Starch is synthesised when high amounts of triose phosphates form in the chloroplast, which can occur when factors prevent export of triose phosphates from the chloroplast.

C. The recycling of inorganic phosphate, released from sucrose synthesis, is necessary for the antiporter to work that brings triose phosphates out of the chloroplast.

D. Sucrose is the primary transport sugar in plants, and can be formed in the cytosol of cells from triose phosphates exported from the chloroplast.

A. The reimport of the inorganic phosphate into the chloroplast is necessary for the production of NADPH in the light-dependent reactions.

B. Starch is synthesized in the chloroplast as a major store of sugar for later use. Starch is synthesised when high amounts of triose phosphates form in the chloroplast, which can occur when factors prevent export of triose phosphates from the chloroplast.

C. The recycling of inorganic phosphate, released from sucrose synthesis, is necessary for the antiporter to work that brings triose phosphates out of the chloroplast.

D. Sucrose is the primary transport sugar in plants, and can be formed in the cytosol of cells from triose phosphates exported from the chloroplast.

Explanation / Answer

Starch is synthesized in the chloroplast as a major store of sugar for later use. Starch is synthesised when high amounts of triose phosphates form in the chloroplast, which can occur when factors prevent export of triose phosphates from the chloroplast.

The formation of starch occurs not because the export of the triose phosphates is prevented but because most of the triose phosphates do not continue in the calvin cycle. The remaining triose phosphates condense to form starch and cellulose. This is not affected by the transport of triose phosphates.

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