Photosynthesis (HL IB Environmental Systems & Societies (ESS))

Photosynthesis

What is photosynthesis?

• Primary producers in the majority of ecosystems convert light energy into chemical energy in the process of photosynthesis

  • Producers are typically plants, algae and photosynthetic bacteria that produce their own food using photosynthesis

    • They are also known as autotrophs

  • Producers form the first trophic level in a food chain

  • The photosynthesis reaction is:

• The inputs and outputs are:

  • Inputs: sunlight as an energy source, carbon dioxide, and water

  • Processes: inside chloroplasts, chlorophyll captures certain visible wavelengths of sunlight energy and stores this as chemical energy

  • Outputs: glucose and oxygen

  • Transformations: light energy is transformed into stored chemical energy (in the form of glucose)

• Photosynthesis produces the raw material for producing biomass

  • The glucose produced during photosynthesis is used as an energy source for the plant but also as the basic starting material for other organic molecules (e.g. cellulose and starch)

• In ecosystems where sunlight and water are available, the process of photosynthesis enables plants to synthesise these organic compounds (glucose and other sugars) from carbon dioxide

• Most of these sugars synthesised by plants are used by the plant as respiratory substrates

  • A respiratory substrate is a molecule (such as glucose) that can be used in respiration, to release energy for growth