Photosynthesis: Using Light to Make Food

Introduction to Photosynthesis

Photosynthesis is a fundamental biological process that converts solar energy into chemical energy, providing the basis for most life on Earth. This process is essential for the production of organic molecules that serve as food for living organisms.

• Biofuels are energy sources derived from living materials. When we use biofuels, we are ultimately utilizing energy originally captured from the sun by living cells.

• In living cells, solar energy is converted into the chemical energy of sugars through photosynthesis.

• This chapter focuses on the mechanisms and significance of photosynthesis.

Photosynthesis Powers Most Life on Earth

Photosynthesis is the primary process by which energy from sunlight is captured and used to sustain life. It is performed by a variety of organisms and supports both producers and consumers in ecosystems.

• Photoautotrophs are organisms (such as plants, algae, and some protists and bacteria) that produce their own food using light energy. They are the primary producers in most ecosystems.

• Heterotrophs are organisms that cannot produce their own food and must consume other organisms (plants, animals, or decomposed organic material) for energy.

• Key Point: Photoautotrophs require sunlight, carbon dioxide (CO2), and water (H2O) from the environment to synthesize their own food.

• Example: Green plants in a forest, algae in the ocean, and cyanobacteria in freshwater are all photoautotrophs that support food webs.

Key Terms

• Autotroph: An organism that makes its own food from inorganic substances.

• Photoautotroph: An autotroph that uses light energy to drive the synthesis of organic compounds.

• Heterotroph: An organism that obtains organic food molecules by eating other organisms or their by-products.

Visual Representation

Images (as seen in Figure 7.1) typically show lush plant life, underwater algae, and microscopic views of plant cells, all illustrating the diversity of photoautotrophs.