Biological Concepts Related to Photosynthesis and Autotrophy

Types of Organisms

• Autotrophs: Organisms that produce their own food.
  • Photoautotrophs: Use sunlight to synthesize foods.
  • Chemoautotrophs: Obtain energy from chemical reactions.
• Heterotrophs: Organisms that cannot produce their own food and must consume other organisms for energy.

Photosynthesis

• Definition: The process through which green plants and some other organisms use sunlight to synthesize foods with the help of chlorophyll.
• Occurs in: Chloroplasts, specifically in the thylakoids.

Key Components

• Chlorophyll: The green pigment in plants that absorbs light energy.
• Thylakoids: Membrane-bound compartments inside chloroplasts where light-dependent reactions occur.
• Stroma: The fluid-filled space surrounding the thylakoids in chloroplasts where the Calvin cycle occurs.
• Guard Cells: Cells surrounding stomata that regulate gas exchange and water loss.

Photosynthetic Process

• Light-dependent reactions: Occur in the thylakoids, converting sunlight into energy (ATP and NADPH).
• Calvin Cycle (Light-independent reactions): Takes place in the stroma, uses ATP and NADPH to convert carbon dioxide into glucose.

Key Terms

• Stomata: Pores on the leaf surface that allow gas exchange.
• Epidermis: The outer layer of cells in leaves that protects against water loss.

Light and Pigments

• Wavelength: The distance between successive peaks of a wave, affects the type of energy absorbed by pigments.
• Pigments involved in photosynthesis:
  • Chlorophyll A: Primary pigment, absorbs violet-blue and red light.
  • Chlorophyll B: Accessory pigment that helps in trapping light energy.

Additional Concepts

• Photorespiration: A process that occurs when the enzyme RuBisCO fixes oxygen instead of carbon dioxide, leading to a loss of carbon and energy in plants. This usually occurs when oxygen levels are high and carbon dioxide levels are low due to environmental conditions.