Which of the following is an output (product) of the Calvin cycle during photosynthesis?
A NADPH
B Rubisco
C Glucose
D CO2
E ATP
The correct answer and explanation is:
The correct answer is C. Glucose.
The Calvin cycle, also known as the dark reaction or the light-independent reaction, is a part of photosynthesis that occurs in the stroma of the chloroplast. It is responsible for converting carbon dioxide into glucose using energy from ATP and NADPH, which are produced during the light-dependent reactions. The Calvin cycle does not directly use light energy, but it relies on the products of the light reactions to drive the process.
The Calvin cycle can be divided into three main stages: carbon fixation, reduction, and regeneration of RuBP (ribulose bisphosphate).
- Carbon Fixation: The enzyme Rubisco attaches carbon dioxide to a five-carbon sugar called RuBP, resulting in a six-carbon compound that immediately splits into two molecules of 3-phosphoglycerate (3-PGA).
- Reduction: ATP and NADPH from the light-dependent reactions are used to convert 3-PGA into glyceraldehyde-3-phosphate (G3P), a three-carbon sugar. G3P can then be used to form glucose and other carbohydrates.
- Regeneration: Some of the G3P molecules are recycled to regenerate RuBP, allowing the cycle to continue.
The ultimate product of the Calvin cycle is glucose, which can then be used by the plant for energy and growth. While ATP and NADPH are necessary for the cycle, they are consumed and not directly produced by it. Rubisco is the enzyme involved in carbon fixation, and CO2 is the substrate being converted into organic molecules.
Thus, glucose is the key output of the Calvin cycle, synthesized through a series of chemical reactions that transform carbon dioxide into organic compounds. This process plays a vital role in the overall function of photosynthesis, enabling plants to store energy in the form of carbohydrates.