Photosynthesis

• A life on earth is possible because of energy from sun
• Organisms receive energy directly or Indirectly
• ATP provides energy for:


  • Active transport of ions and molecules across cell membranes
  • Moving chromosomes during cell division
  • Causing cilia and flagella to move
  • Causing muscle contractions
  • Synthesizing macromolecules
• Energy from ATP comes from bond between the 2nd and 3rd phosphate groups in ATP
• ATP is broken down and regenerated thousands of times each day
• Cellular Reactions

  1. (Endothermic) Photosynthesis: 6CO2(g)+ 6H2O(l)+ light energy -> C6H12O6(s) + 6O2(g)

  2. (Exothermic) Cellular Respiration: C6H12O6(s) + 6O2(g) -> 6CO2(g) + 6H2O(l) + 36 ATP

  *These reactions occur through a process called Metabolic pathways
• Types of metabolic pathways

  • Anabolic pathways (synthesize larger molecules and require energy, ex// photosynthesis)
  • Catabolic pathways (break down larger molecules and release energy, ex// cellular respiration)
• Oxidation-Reduction Reactions (Redox)

  Process where oxidation and reduction must occur together because electrons don't exist on their own
• Atoms and compounds contain more energy in their reduced form
• Molecules with large amounts of available energy are said to have reducing power
• "LEO the lion says GER" or "OIL RIG" is a mnemonic for remembering oxidation and reduction
• Metabolism refers to all chemical reactions that happen inside cells to support/sustain life functions (catalysed by enzymes)
• (GOLD)(ATP) A-P-P~P

  *energy release*

  (SILVER)(ADP) A-P-P

  *energy release*

  (BRONZE)(AMP) A-P

  (~) means high energy bond
• Oxidation-Reduction Reaction diagram:

  
• Redox diagram (also known as "Oil Rig"):

  
• L loss

  E electrons

  O oxidation

  G gain

  E electrons

  R reduction
• Photosynthesis


  Stores energy in organic compounds
• Pigments (play a huge role in photosynthesis)

  Compound that absorbs certain wavelengths of visible light while reflecting others (arranged in photosynthesis)
• Chlorophyll


  Main pigment in plants
• Beta carotene

  Carotenoid pigment that converts to vitamin A and is the visual pigment for our eyes
• Carotenoids


  Protect chlorophyll in plants from being destroyed
• The drop in colour spectrum is the colours we see (refer to light spectrum)
• Each photosynthetic pigment absorbs light of different colours
• More pigment = greater percentage of sun's energy trapped
• Inner membrane


  Forms a border to the stroma and regulates passage of materials in and out of the chloroplast (site where fatty acids, lipids, and carotenoids are synthesized)
• Stroma


  Fluid in the inner space of the chloroplast that contains a concentrated mixture of proteins and other chemicals used in the synthesis (making) of carbohydrates
• Thylakoids


  Contain chlorophyll molecules and can be stacked up in structures called Grana (thylakoids are interconnected flattened sacs)
• Outer membrane


  signals transduction, protein import, and lipid biosynthesis
• Photosynthesis reactions

  • Light dependent reactions
  • Light independent reactions
• Light dependent reactions


  • Require light
  • Occur in thylakoid discs
• Light independent reactions


  • Don't require light
  • Occur in stroma
• Molecules produced in LD (light dependant) reactions

  • O2 gas (from photolysis of water)
  • ATP (through chemiosmosis)
  • NADPH (last electron acceptor)
• ATP and NADPH


  high energy compounds that proceed to the light independent reactions for the production of sugars (glucose)
• NADP+

  Undergoes reduction to become NADPH (a compound with reducing power)
• As electrons move down the electron transport chain (ETC)


  1. Small amounts of energy are released

  2. H+ ions (protons) move from the stroma into the thylakoid space against the concentration gradient

  3. H+ ions move back into the stroma down the concentration gradient through ATP Synthase

  4. ATP is produced (chemiosmosis)
• Chloroplast diagram:

  A) inner membrane

  B) outer membrane

  C) middle layer

  D) Granum

  E) lumen

  F) stroma

  G) thylakoid

  
• Autotrophs - organisms that can produce its own food using light, water, CO2, or other chemicals (ex// plants)
• Heterotrophs - organisms that eat other plants or animals for energy and nutrients (ex// humans)
• Light independent reactions

  • ATP and NADPH (already produced in light reactions) move Into the Stroma where they are used to make glucose in the Calvin-Benson cycle
• Calvin-Benson cycle events

  1. CO2 Fixation

  2. Reduction

  3. Regenerating RuBP