Photosynthesis in Plants Answers

Photosynthesis is vital for plant life, because it provides plants with a means to produce energy. Photosynthesis indirectly provides organisms that feed on plants with energy as well. Organisms that feed on plants derive their energy from the plants, which obtained their energy from sunlight through the process of photosynthesis. Photosynthesis also helps maintain atmospheric levels of carbon dioxide and oxygen. Carbon dioxide is taken in by plants during photosynthesis, and oxygen is released.

The light reactions occur when light is absorbed by the chlorophyll in plants. This light energy is converted to chemical energy in the thylakoids of the chloroplasts in the form of ATP and NADPH. Water splits, producing oxygen gas which is released through the stomata on plant leaves. The dark reactions occur in the stroma of the chloroplasts when carbon dioxide is converted to sugar using energy derived from ATP and NADPH.

There are different types of carbon fixation, because plants are located in regions with different conditions. Plants that live in arid regions need to conserve water, while plants that live in more moist conditions will not need to conserve water. Plants that live in dry areas, or areas with higher temperatures have adapted modified methods of carbon fixation to help maximize their efficiency.

C3 plants are adapted to moderate temperatures and sunlight. C3 carbon fixation is the process used for most plants. In C3 carbon fixation, carbon dioxide first combines with a 3-carbon compound while in C4 carbon fixation, carbon dioxide first combines with a 4-carbon compound. Plant stomata are open during the day in both types of carbon fixation. In C3 plants, carbon fixation occurs throughout the leaf. The 4-carbon compound made in plants using C4 carbon fixation is used to deliver carbon dioxide to inner cells of the leaf.