光合作用：練習題

Which of the following is a component of a chloroplast where the light-independent stage of photosynthesis takes place?

In the light-independent stage of photosynthesis, what is the role of the enzyme RuBisCO?

Which of the following best describes the process of cyclic photophosphorylation in the light-dependent stage?

During photosynthesis, what is the role of water in the light-dependent stage?

Which statement correctly describes the interrelationship between photosynthesis and respiration in plants?

Explain how water stress in a plant leads to a decrease in the rate of photosynthesis, specifically referring to the levels of ribulose bisphosphate (RuBP) and glycerate 3-phosphate (GP).

Photosynthesis occurs in the chloroplasts of eukaryotic plants and involves complex biochemical pathways influenced by various environmental factors. Consider a situation where a plant is subjected to a significant reduction in light intensity.

(a) Describe and explain the effect of decreasing light intensity on the concentration of ribulose bisphosphate (RuBP) and glycerate 3-phosphate (GP) within the stroma of the chloroplast. (3 points)

(b) Explain how energy from light is harvested and used to drive the production of chemicals in the light-dependent stage, specifically mentioning the role of water and the process of photophosphorylation. (4 points)

(c) Some herbicides act by binding to proteins in the electron transport chain within the thylakoid membrane. Suggest and explain why such a herbicide would ultimately lead to the cessation of the Calvin cycle, even if the enzymes of the Calvin cycle are not directly inhibited. (1 point)

Photosynthesis occurs in two main stages: the light-dependent and light-independent stages. A researcher investigated the effect of light intensity on the concentration of key metabolites in the stroma of a spinach chloroplast.

(a) Explain why a sudden decrease in light intensity results in an initial increase in the concentration of glycerate 3-phosphate (GP). (2 points)

(b) In a separate experiment, the researcher inhibited the enzyme ribulose bisphosphate carboxylase (RuBisCO). Describe and explain the effect this would have on the concentration of triose phosphate (TP). (2 points)

(c) Plants subjected to severe water stress often show a significantly reduced rate of photosynthesis. Explain how the closure of stomata during water stress ultimately affects the regeneration of ribulose bisphosphate (RuBP). (3 points)