Photosynthesis and Natural Product Production

Photosynthesis Overview

• Photosynthesis is the process by which plants, algae, and some bacteria convert light energy from the sun into chemical energy in the form of organic compounds, such as glucose.
• The equation for photosynthesis is: 6CO2 + 6H2O + sunlight → C6H12O6 + 6O2.
• Photosynthesis occurs in two stages: light-dependent reactions and light-independent reactions.

Light-Dependent Reactions

• Occur in the thylakoid membranes of the chloroplast.
• Involve the conversion of light energy into ATP and NADPH.
• Steps:
  • Light absorption by pigments such as chlorophyll a and other accessory pigments.
  • Excitation of electrons and transfer to a special molecule called an electron acceptor.
  • Transfer of electrons through the electron transport chain, losing energy used to pump protons across the membrane.
  • Formation of a proton gradient, which is used to drive the synthesis of ATP from ADP and Pi through chemiosmosis.
  • Reduction of NADP+ to form NADPH.

Light-Independent Reactions (Calvin Cycle)

• Occur in the stroma of the chloroplast.
• Involve the fixation of carbon dioxide into glucose using ATP and NADPH produced in the light-dependent reactions.
• Steps:
  • Carbon fixation: CO2 is combined with ribulose-1,5-Bisphosphate (RuBP) to produce an unstable six-carbon molecule that splits into two 3-phosphoglycerate (3-PGA) molecules.
  • Activation and reduction: ATP and NADPH are used to convert 3-PGA molecules into glyceraldehyde-3-phosphate (G3P).
  • Regeneration: five molecules of G3P are used to regenerate RuBP, and the remaining ½ G3P molecule is used to make glucose.

Significance of Photosynthesis in Production of Natural Products

• Biomass production: provides raw material for various natural products, including food, fiber, biofuels, animal feed, and more.
• Organic compound synthesis: produces a wide range of organic compounds, such as carbohydrates, amino acids, lipids, phenolics, and terpenes.
• Phytochemical production: produces biologically active compounds with medicinal and industrial applications, such as antioxidants, anti-inflammatory agents, antibiotics, and anticancer agents.
• Ecosystem support: produces oxygen and organic compounds that support the food chain, including oxygen for aerobic organisms, food for herbivores, and shelter and habitat for wildlife.