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  1. 1. PHOTOSYNTHESISPhotos (light) + synthesis (put together ormanufature)
  2. 2. Plants… Harness energy from the sun through chloroplasts Then store the energy converted into carbohydrate molecules in the cell wall and vacuoles Undergo PHOTOSYNTHESIS - the process by which plants convert energy from the sun to provide energy for themselves and almost all life forms
  3. 3. Photosynthesis… Allows plants to create organic molecules they use as fuel. Basis of all food chains Occurs mostly in LEAVES, which are the main organs for photosynthesis
  4. 4. Photosynthesis
  5. 5. Chloroplasts Organelles specialized for photosynthesis Have two membranes surrounding the liquid in its interior called the STROMA Inside the inner membrane are series of flattened interconnected sacs called GRANA Each of these flattened sacs is called a THYLAKOID
  6. 6. Chloroplasts (cont’d) A closer look at the thylakoid will reveal its membrane separating it with the stroma or the liquid part of the chloroplast – it is in this membrane that light trapping molecules are located LIGHT DEPENDENT REACTION of photosynthesis – aka PHOTOCHEMICAL STAGE  occurs in thylakoid membrane (because of the light trapping molecules) LIGHT INDEPENDENT REACTION of photosynthesis – aka DARK REACTION/CALVIN CYCLE
  7. 7. Photosynthesis LIGHT and WATER are needed to perform this process (sun heats water in plant leaves) Chlorophyll in chloroplasts (scattered throughout each plant cell), absorb energy in the form of light from the sun Plants take in carbon dioxide – obtained through tiny openings known as stomata Plants absorb water and nutrients dissolved in the soil through their root
  8. 8. Words to Know: PhotosynthesisATP - Adenosine TriphosphateADP - Adenosine DiphosphateNADPH- Nicotinamide Adenine Dinucleotide Phosphate (Hydrogen acceptor)Reactant - substances that undergo chemical reactionProduct - outcome of the reaction
  9. 9. Photosynthesis Equation
  10. 10. Photosynthesis Is the reverse of the reactions that occur in animals during cellular respiration CELLULAR RESPIRATION – the splitting apart of glucose by water to produce carbon dioxide and energy PHOTOSYNTHESIS – the splitting apart of water by energy to produce glucose from carbon dioxide, with oxygen given off
  11. 11. Two Stages of Photosynthesis:Light Dependent Stage Occurs in thylakoid membrane Energy from the sun (light energy) is absorbed by the chlorophyll and then converted into chemical energy. Light energy is needed to split the water molecules into hydrogen and oxygen. Oxygen is released as a waste product. These reactions are called photochemical light reactions because they require light to occur.
  12. 12. Light Dependent Stage Involves two groups of light absorbing molecules found in the thylakoid membranes: Photosystem I and Photosystem II Both capture solar energy to energize electrons. Both cooperate in the light reactions. Photosystem II functions first.
  13. 13. Light Dependent Stage When excited by light from the sun, chlorophylls release energized electrons. The photosystems transfer the energized electrons to electron transport chains. Electrons in Photosystems II that were shuttled to Photosystem I provide energy to make ATP. Electrons from Photosystem I reduce the coenzyme NADP+ (NAD = Nicotinamide adenine dinucleotide) to NADPH. Photosystem II regains electrons by splitting water and releasing oxygen.
  14. 14. Steps: Light Dependent Reaction 1 Light energy is absorbed by 2 Chlorophyll A (becomes an energy carrier) that becomes 3 Energized chlorophyll supplies energy to split combine 4 water 4 phosphate into with 5 ADP to form5 H2 5 O is released that are trapped by 6 ATP6 NADP (H acceptor) forms to be used for dark reaction7 NADPH2 to be used for dark reaction
  15. 15. Light Independent Stage Second stage of photosynthesis Formation of glucose from carbon dioxide doesn’t directly require light. Aka Calvin Cycle for Melvin Calvin Occurs in stroma Consists of cyclical series of reactions that assembles sugar molecules from carbon dioxide and the energy- containing products of the light- dependent reaction with the aid of enzymes.
  16. 16. Light Independent Stage In the stroma, the enzymes combine carbon dioxide with ribulose phosphate (RuBP) which is a five-carbon sugar and produce glyceraldehydes-three-phosphate (G-3-P), an energy-rich, three-carbon sugar formed by the splitting of sugar. G-3-P can be used by a plant cell to make glucose and other organic molecules. The glucose produced during photosynthesis is used by plans as fuel for cellular respiration, and starting material to make cellulose. Excess sugar is combined with a large carbohydrate molecule and stored as starch in their roots, tubers or fruits.
  17. 17. Steps : Light Independent Reaction 1 6 CO2 molecules combines with 2 RuDP (CO2 acceptor) forms 3 6-C sugar (unstable sugar) splits to form 4 2 molecules of PGA (3- C compound)-called: combines withBiochemical Pathway 5 2H (from light reaction (NADPH)) forms 6 2 molecules of PGAL 6 H2O is converted into by-product used 7 in light reaction RuDP to be reused Glucose to combine with CO2
  18. 18. Comparison of the twoReaction Light DarkSite of Occurence Thylakoid-grana stromaInitial Requirement Light Energy, ATP, NADPH, and(Reactants) water, and CO2, chlorophyll AEnd Product ATP, NADPH, Glucose, water, Oxygen NADP, ADP and inorganic phosphateBoth reactions thus form a cycle in which the reactants:water and carbon dioxide produce oxygen and sugar
  19. 19. Plants need: Carbon dioxide Water Oxygen (for cellular respiration) Hydrogen Nitrogen Potassium Phosphorus Calcium Magnesium Sulfur Boron Copper Iron Molybdenum Zinc