Photosynthesis

• Photosynthesising organisms are ‘photoautotrophs’; they use light as energy source for autotrophic nutrition; ‘producers’ at first trophic level of food chain, provide energy and organics molecules to other, non-photosynthetic, organisms
• Organisms that use chemical energy as their energy source for autotrophic nutrition are called ‘chemoautotrophs’; typically bacteria and can oxidise inorganic compounds
• Plants and other photosynthesising organisms also respire, during respiration, they oxidise organic molecules they previously synthesised by photosynthesis and stored, releasing chemical energy
• Heterotrophs: Non-photosynthetic organisms (fungi, animals, protoctists, and many bacteria) obtain energy by digesting complex food molecules into smaller respiratory substrates
• Physiological process used by plants, algae and some bacteria to convert light energy from sunlight into chemical energy; which synthesises large organic molecules, living cells building blocks, from simple inorganic molecules; autotrophic nutrition
• Light energy is converted to chemical energy, and H_2O is broken down to release O2 and H+ ions, which reduce CO_2, which is then fixed (complex organic molecules are synthesised from simpler inorganic ones) - oversimplified equation:

  A) Carbon Dioxide

  B) Water

  C) Glucose

  D) Oxygen

  E) 6CO_2

  F) 6H_2O

  G) C_6H_12O_6

  H) 6O_2

  
• Photosynthesis is a two-stage process: Light-dependent reaction (occurs on thylakoids and only during daylight) and light-independent reaction (occurs in the stroma and may continue in dark); also called Calvin Cycle
• Input and Output

  A) water

  B) Light energy

  C) NADP/ADP/Pi

  D) Reduced NADP

  E) ATP

  F) O_2

  G) Reduced NADP

  H) ATP

  I) CO_2

  J) Glucose

  K) NADP/ADP/Pi