The Calvin Cycle 6-2 Notes w/ Vocab

Describe what can happen to the three-carbon molecules made in the Calvin cycle

Most of the three carbon G3P is used to make more RuBP, keeping the Calvin cycle operating. Some G3P is converted into other organic compounds, including amino acids, lipids, and carbohydrates.

The Calvin Cycle

The ATP and NADPH produced in the light reactions drive the second stage of photosynthesis, the Calvin cycle. In the Calvin cycle, carbon dioxide is incorporated into organic compounds, a process called carbon fixation. The Calvin cycle produces a compound called G3P. Most G3P molecules are converted into RuBP to keep the Calvin Cycle operating. However, some G3P molecules are used to make other organic compounds, including amino acids, lipids, and carbohydrates. Plants that fix carbon using only the Calvin cycle are known as C3 plants. Some plants that evolved in hot, dry climates fix carbon through alternative pathways - the C4 and CAM pathways. THese plants, carry out carbon fixation and the Calvin cycle either in different cells or at different times. Photosynthesis occurs in two stages. In the light reactions, energy is absorbed from sunlight and converted into a chemical energy; in the Calvin cycle, carbon dioxide and chemical energy are used to form organic compounds. The rate of photosynthesis increases and then reaches a plateau as light intensity or CO2 concentration increases. Below a certain temperature, the rate of photosynthesis increases as temperature increases. Above that temperature, the rate of photosynthesis decreases as temperature increases.

Name the part of the chloroplast where the Calvin cycle takes place.

The Calvin cycle takes place in the stroma of the chloroplast

Carbon Fixation

The incorporation of carbon from carbon dioxide into an organic compound by an autotrophic organism.

C4 Pathway

a carbon-fixing process in which carbon dioxide is bound to a compound to form a four-carbon intermediate

Calvin Cycle

A biochemical pathway of photosynthesis in which carbon dioxide is converted into glucose using ATP and NADPH.

Stomata

A microscopic pore surrounded by guard cells in the epidermis of leaves and stems that allows gas exchange between the environment and the interior of the plant.

CAM Pathway

A water-conserving, carbon-fixing process; CAM plants take in carbon at night and fix it into various organic compounds and release it during the day.

Explain why the light reactions and the Calvin cycle are dependent on each other

ATP and NADPH, which are formed during the light reactions, are both used in the Calvin cycle. The Calvin cycle produces ADP, NADP+, and phosphates that are used in the light reactions.

Explain why increased light intensity might not result in an increased rate of photosynthesis.

If all available electrons in chlorophyll are excited, increasing light intensity will have no effect on photosynthesis.

Distinguish between C3, C4, and CAM plants

In C3 plants, carbon dioxide continually enters the Calvin cycle, and a three-carbon compound is made. A C4 pant fixes carbon dioxide into four-carbon organic compounds in certain cells. CAM plants fix carbon dioxide at night.