Photosynthesis

Definition

Photosynthesis is the process by which green plants, algae, and some bacteria convert light energy into chemical energy stored in glucose, using carbon dioxide and water as raw materials. This process is crucial for life on Earth, as it forms the foundation of the food chain and plays a significant role in cycling carbon and oxygen through ecosystems.

5 Must Know Facts For Your Next Test

1. Photosynthesis primarily occurs in the leaves of plants, specifically within specialized cells called mesophyll that contain chloroplasts.
2. The overall chemical equation for photosynthesis can be summarized as: 6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ + 6O₂.
3. Photosynthesis is divided into two main stages: the light-dependent reactions, which capture energy from sunlight, and the light-independent reactions (Calvin cycle), which use that energy to synthesize glucose.
4. Oxygen produced during photosynthesis is a byproduct that is released into the atmosphere, supporting aerobic life forms.
5. The efficiency of photosynthesis can be affected by several factors, including light intensity, carbon dioxide concentration, temperature, and water availability.

Review Questions

• How does photosynthesis contribute to the carbon cycle and support life on Earth?
  • Photosynthesis plays a vital role in the carbon cycle by taking in carbon dioxide from the atmosphere and converting it into organic compounds like glucose. This process not only provides essential energy for plants but also forms the basis of food for herbivores and subsequently for carnivores. By releasing oxygen as a byproduct, photosynthesis supports aerobic organisms and contributes to maintaining atmospheric balance.
• What are the differences between light-dependent reactions and light-independent reactions in photosynthesis?
  • Light-dependent reactions occur in the thylakoid membranes of chloroplasts where sunlight is absorbed by chlorophyll, leading to the production of ATP and NADPH while splitting water molecules to release oxygen. In contrast, light-independent reactions, known as the Calvin cycle, take place in the stroma where ATP and NADPH generated from light-dependent reactions are used to convert carbon dioxide into glucose. Thus, these two stages work together to transform solar energy into chemical energy.
• Evaluate how environmental factors such as light intensity and temperature affect the rate of photosynthesis.
  • Environmental factors like light intensity and temperature have a significant impact on the rate of photosynthesis. Increased light intensity typically enhances photosynthetic activity up to a certain point until other factors become limiting. Similarly, temperature affects enzyme activity involved in photosynthesis; optimal temperatures can boost rates while extreme heat or cold can inhibit them. Understanding these relationships helps in assessing how plants respond to changing environments due to climate change.

Related terms

Chlorophyll: A green pigment found in the chloroplasts of plants that absorbs light energy, primarily from the sun, to drive photosynthesis.

Respiration: The process by which organisms convert glucose and oxygen into energy, carbon dioxide, and water, essentially the reverse of photosynthesis.

Carbon Cycle: The series of processes by which carbon atoms are recycled through the atmosphere, land, oceans, and living organisms, with photosynthesis being a key component.