photosynthesis

• Photosynthesis is a reaction where light energy is converted to chemical energy in the form of glucose, with oxygen released as a waste product
• Photosynthesis occurs in chloroplasts, which are adapted for photosynthesis with stacks of thylakoid membranes called grana containing photosynthetic pigments like chlorophyll, and stroma containing enzymes for the light-independent stage
• Leaves of C4 plants like maize and sorghum are adapted to work at high temperatures, fixing carbon dioxide into a four carbon organic acid called malate in mesophyll cells before transporting it to photosynthetic cells to ensure a high concentration of carbon dioxide for efficient photosynthesis
• Photosynthetic pigments, like chlorophylls and carotenoids, absorb light for photosynthesis and convert it to chemical energy, with chlorophylls absorbing red and blue-violet light and reflecting green light
• An absorption spectrum determines the wavelengths absorbed by pigments, while an action spectrum illustrates the relationship between the rate of photosynthesis for a given wavelength
• Photosynthetic pigments can be separated by extracting them from a leaf and carrying out chromatography, where the Rf value can be used to identify which pigments are present
• Photosynthesis has two stages:

  • Light-dependent reaction: involves photoionization, electron transport chain, ATP production via chemiosmosis, photolysis of water, and generation of reduced NADP and ATP
  • Light-independent reaction (Calvin cycle): uses ATP and reduced NADP from the light-dependent stage to produce glucose in the stroma
• Limiting factors of photosynthesis include carbon dioxide concentration, light intensity, light wavelength, and temperature, with the rate increasing as these factors increase but slowing at high light intensities and temperatures due to potential leaf damage and enzyme denaturation