Topic 2 (Photosynthesis)

• Photosynthesis is vital to all life:

  • The oxygen in the air (20%) came originally from plants photosynthesizing
  • All food comes (indirectly or directly) from photosynthesis, therefore the sun
• Through photosynthesis, producers (plants) capture and store sunlight energy.

  The energy is stored in the chemical bonds of different molecules, including sugars (direct), fats, amino acids, and nucleotides (indirect)
• Plant cells have chloroplasts which contain chlorophyll that absorbs light energy.
• Chlorophyll is green because it reflects green wavelengths while absorbing other colors.
• The energy in the food molecules came directly from producers, or from animals that have eaten producers
• In almost all producers, photosynthesis occurs in chloroplasts
• Pigments in the chloroplasts capture radiant energy from the sun.
• Chlorophyll is green. It absorbs red and blue colors on the visible light spectrum and reflects green light.

  Phototrophic organisms that do not have chloroplasts contain chlorophyll pigments.
• Carotene(red-orange) and xanthophylls (yellow) pigments are usually covered by green chlorophylls. In autumn, when leaves stop making chlorophyll, red, orange, and yellow pigments become visible.
• Light dependent (light reactions) - light energy is absorbed by chlorophyll and converts to ATP and NADPH. H2O is split into hydrogen and oxygen. The O2 (byproduct of photosynthesis), is released from the cell.
• Light independent (dark reactions): energy stored in ATP and NADPH during the light dependent reactions and CO2 are used to produce glucose (Calvin cycle)
• Net reaction for photosynthesis:


  6 CO2 + 6H2O + energy -> C6H12O6 + 6O2
• The process whereby plants capture the sun's energy and store it in the form of chemical bonds in carbohydrate molecules (sugars)

  Photosynthesis
• all animals, many microorganisms that obtain energy from the chemical bonds of food molecules that they have eaten

  Consumers
• All energy that is used by all organisms comes from the sun.
• The Chloroplast

  • In eukaryotic cells
  • Double membrane that contains chlorophyll
  • Performs photosynthesis (Receives photons)
  • Major organ of a plant that is photosynthetic is the leaf
• Endosymbiotic Theory


  Photosynthesis originated from small eukaryotic cells that contained chloroplasts being protected inside of larger cells.

  Large cells receive glucose from photosynthetic smaller cells

  Small cells receive protection
• Stroma


  Protein-rich semi-liquid material inside chloroplast

  
• Thylakoid


  A system of stacked membrane-bound sacs inside the chloroplast
• Thylakoid Membrane


  Contains thylakoid and lumen
• Lumen


  Aqueous substance
• Chloroplasts are able to replicate independently of the cell.

  Chloroplasts have individual DNA
• • Cellular functions
  • immediate source of energy for growth, movement, all chemical reactions
  • Intermediate energy source


  ATP
• • Energy transfers with 2 electrons and H ions

  NADPH/NADP
• • Transported by blood (Blood sugar)
  • Medium-term energy storage in most cells


  Glucose
• ATP -> ADP + Pi
• ADP -> AMP + Pi
• NADPH transports 2 electrons along ETC