Respuesta :
The true statments are: Light-independent reactions requires carbon dioxide (CO2) and Light-independent reactions produce carbohydrates.
The light-independent reactions are the second stage of photosynthesis, also called dark reactions because they are not directly driven by light. These reactions convert carbon dioxide (CO2) and other compounds into glucose. Unlike the light-dependent reactions (first stage of photosynthesis), which take place in the thylakoid membrane, the reactions of the Calvin cycle take place in the stroma (the inner space of chloroplasts). Dark reactions take the products (ATP and NADPH) of light-dependent reactions and use it for further chemical processes. Light-independent reactions known as the Calvin cycle consists of three phases: carbon fixation, reduction reactions, and regeneration of the starting molecule-ribulose 1,5-bisphosphate (RuBP).
1. Carbon fixation: CO2 bounds to acceptor molecule, ribulose-1,5-bisphosphate (RuBP) and forms six-carbon compound that splits into two molecules of 3-phosphoglyceric acid (3-PGA). This reaction is catalyzed by the enzyme RuBP carboxylase/oxygenase, or rubisco.
2. Reduction: 3-PGA molecules are converted into glyceraldehyde-3-phosphate (G3P). ATP and NADPH are used for converting and during this stage NADPH donates electrons (reduces) to a three-carbon intermediate to make G3P.
3. Regeneration: G3P molecules are used to make glucose, or are recycled to regenerate the RuBP acceptor. Regeneration requires ATP.
Three turns of the Calvin cycle are needed to make one G3P molecule. A G3P molecule contains three fixed carbon atoms, so it takes two G3Ps to build a glucose, which contains six carbons. To produce one molecule of glucose, it would take six turns of the cycle.
