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Photosynthesis and Cellular Respiration

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Photosynthesis and Cellular Respiration. How do cells obtain organic compounds for energy?. Heterotrophs : Cannot make their own food Autotrophs : Can make their own food Photoautotrophs : Use energy from the sun (photosynthesis) to produce organic compounds (glucose) - PowerPoint PPT Presentation

Text of Photosynthesis and Cellular Respiration

  • Photosynthesis and Cellular Respiration

  • How do cells obtain organic compounds for energy?Heterotrophs: Cannot make their own foodAutotrophs: Can make their own foodPhotoautotrophs: Use energy from the sun (photosynthesis) to produce organic compounds (glucose)Plants, algae and some bacteriaChemoautotrophs: Use energy stored in inorganic compounds (chemosynthesis) to produce organic compoundsSome bacteria found at the hydrothermal vents of the seafloor

  • PhotosynthesisMethod of converting light energy from the sun into chemical energy that cells can use Divided into the light-dependent and light-independent reactionsPhotosynthesis takes place in chloroplastsThe parts of a chloroplast are as follows:Thylakoids- disk-shaped structures that contain the pigment chlorophyll (absorbs the sunlight)Grana- A stack of thylakoidsStroma- Liquid between grana

  • Draw a Chloroplast

  • Overall Photosynthesis Reaction 6CO2 + 6 H2O + light energy C6H12O6 + 6O2

    On the left of the arrow are the reactants (the components that react together).On the right of the arrow are the products. Identify how a plant obtains the reactants.

  • Light-dependent ReactionsChlorophyll (in thylakoids) absorbs the light energyPlants have 2 types: Chlorophyll A and Chlorophyll BWater molecules are split apart producing H and O2Electrons flow throughout the thylakoid membrane (electron transport chain)Energy compounds ATP and NADPH are produced

  • Light-independent Reactions (Dark Reactions)Occur in the stromaATP and NADPH from the light reactions are used to fuel the break down of CO2 and the reassembling of the atoms to produce glucose.This reassembling is called carbon fixation.Carbon fixation occurs in a series of reactions called the Calvin Cycle.

  • Harvesting Chemical EnergySo we see how energy enters food chains (via autotrophs) we can look at how organisms use that energy to fuel their bodies.Plants and animals both use products of photosynthesis (glucose) for metabolic fuelHeterotrophs: must take in energy from outside sources, cannot make their own e.g. animalsWhen we take in glucose (or other carbs), proteins, and fats-these foods dont come to us the way our cells can use them

  • Cellular Respiration OverviewTransformation of chemical energy in food into chemical energy cells can use: ATPThese reactions proceed the same way in plants and animals. Process is called cellular respirationOverall Reaction:C6H12O6 + 6O2 6CO2 + 6H2O

  • Cellular Respiration OverviewBreakdown of glucose begins in the cytoplasm: the liquid matrix inside the cellAt this point life diverges into two forms and two pathwaysAnaerobic cellular respiration (aka fermentation)Aerobic cellular respiration

  • C.R. ReactionsGlycolysisSeries of reactions which break the 6-carbon glucose molecule down into two 3-carbon molecules called pyruvateProcess is an ancient one-all organisms from simple bacteria to humans perform it the same wayYields 2 ATP molecules for every one glucose molecule broken downYields 2 NADH per glucose molecule

  • Anaerobic Cellular RespirationSome organisms thrive in environments with little or no oxygenMarshes, bogs, gut of animals, sewage treatment pondsNo oxygen used= anaerobicResults in no more ATP, final steps in these pathways serve ONLY to regenerate NAD+ so it can return to pick up more electrons and hydrogens in glycolysis.End products such as ethanol and CO2 (single cell fungi (yeast) in beer/bread) or lactic acid (muscle cells)

  • Aerobic Cellular Respiration Oxygen required=aerobic2 more sets of reactions which occur in a specialized structure within the cell called the mitochondria1. Krebs Cycle2. Electron Transport Chain

  • Krebs CycleCompletes the breakdown of glucoseTakes the pyruvate (3-carbons) and breaks it down, the carbon and oxygen atoms end up in CO2 and H2OHydrogens and electrons are stripped and loaded onto NAD+ and FAD to produce NADH and FADH2Production of only 2 more ATP but loads up the coenzymes with H+ and electrons which move to the 3rd stage

  • Electron Transport ChainElectron carriers loaded with electrons and protons from the Krebs cycle move to this chain-like a series of steps (staircase).As electrons drop down stairs, energy released to form a total of 32 ATPOxygen waits at bottom of staircase, picks up electrons and protons and in doing so becomes water

  • Energy Tally36 ATP for aerobic vs. 2 ATP for anaerobic

    Glycolysis 2 ATP

    Krebs 2 ATP

    Electron Transport32 ATP 36 ATPAnaerobic organisms cant be too energetic but are important for global recycling of carbon

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