Photosynthesisand cellularrespirationpost


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Photosynthesisand cellularrespirationpost

  1. 1. Photosynthesis and Cellular Respiration
  2. 2. Outline <ul><li>I. Photosynthesis </li></ul><ul><ul><li>A. Introduction </li></ul></ul><ul><ul><li>B. Reactions </li></ul></ul><ul><li>II. Cellular Respiration </li></ul><ul><ul><li>A. Introduction </li></ul></ul><ul><ul><li>B. Reactions </li></ul></ul>
  3. 3. Photosynthesis <ul><li>Method of converting sun energy into chemical energy usable by cells </li></ul><ul><li>Autotrophs : self feeders, organisms capable of making their own food </li></ul><ul><ul><li>Photoautotrophs : use sun energy e.g. plants photosynthesis-makes organic compounds (glucose) from light </li></ul></ul><ul><ul><li>Chemoautotrophs : use chemical energy e.g. bacteria that use sulfide or methane chemosynthesis-makes organic compounds from chemical energy contained in sulfide or methane </li></ul></ul>
  4. 4. Photosynthesis <ul><li>Photosynthesis takes place in specialized structures inside plant cells called chloroplasts </li></ul><ul><ul><li>Light absorbing pigment molecules e.g. chlorophyll </li></ul></ul>
  5. 5. Overall Reaction <ul><li>6CO 2 + 12 H 2 O + light </li></ul><ul><li>energy -> C 6 H 12 O 6 + 6O 2 + 6H 2 O </li></ul><ul><li>Carbohydrate made is glucose </li></ul><ul><li>Water appears on both sides because 12 H 2 O molecules are required and 6 new H 2 O molecules are made </li></ul><ul><li>Water is split as a source of electrons from hydrogen atoms releasing O 2 as a byproduct </li></ul><ul><li>Electrons increase potential energy when moved from water to sugar therefore energy is required </li></ul>
  6. 6. Light-dependent Reactions <ul><li>Overview : light energy is absorbed by chlorophyll molecules-this light energy excites electrons and boosts them to higher energy levels. They are trapped by electron acceptor molecules that are poised at the start of a neighboring transport system. The electrons “fall” to a lower energy state, releasing energy that is harnessed to make ATP </li></ul>
  7. 7. Energy Shuttling <ul><li>Recall ATP : cellular energy-nucleotide based molecule with 3 phosphate groups bonded to it, when removing the third phosphate group, lots of energy liberated= superb molecule for shuttling energy around within cells . </li></ul><ul><li>Other energy shuttles-coenzymes (nucleotide based molecules) : move electrons and protons around within the cell </li></ul><ul><ul><li>NADP+, NADPH NAD+, NADP FAD, FADH 2 </li></ul></ul>
  8. 8. Light-dependent Reactions <ul><li>Photosystem : light capturing unit, contains chlorophyll, the light capturing pigment </li></ul><ul><li>Electron transport system : sequence of electron carrier molecules that shuttle electrons, energy released to make ATP </li></ul><ul><li>Electrons in chlorophyll must be replaced so that cycle may continue-these electrons come from water molecules, Oxygen is liberated from the light reactions </li></ul><ul><li>Light reactions yield ATP and NADPH used to fuel the reactions of the Calvin cycle (light independent or dark reactions) </li></ul>
  9. 11. Calvin Cycle (light independent or “dark” reactions) <ul><li>ATP and NADPH generated in light reactions used to fuel the reactions which take CO 2 and break it apart, then reassemble the carbons into glucose. </li></ul><ul><li>Called carbon fixation : taking carbon from an inorganic molecule (atmospheric CO 2 ) and making an organic molecule out of it (glucose) </li></ul><ul><li>Simplified version of how carbon and energy enter the food chain </li></ul>
  10. 13. Harvesting Chemical Energy <ul><li>So we see how energy enters food chains (via autotrophs) we can look at how organisms use that energy to fuel their bodies. </li></ul><ul><li>Plants and animals both use products of photosynthesis (glucose) for metabolic fuel </li></ul><ul><li>Heterotrophs : must take in energy from outside sources, cannot make their own e.g. animals </li></ul><ul><li>When we take in glucose (or other carbs), proteins, and fats- these foods don’t come to us the way our cells can use them </li></ul>
  11. 14. Cellular Respiration Overview <ul><li>Transformation of chemical energy in food into chemical energy cells can use: ATP </li></ul><ul><li>These reactions proceed the same way in plants and animals. Process is called cellular respiration </li></ul><ul><li>Overall Reaction: </li></ul><ul><ul><li>C 6 H 12 O 6 + 6O 2 -> 6CO 2 + 6H 2 O </li></ul></ul>
  12. 15. Cellular Respiration Overview <ul><li>Breakdown of glucose begins in the cytoplasm: the liquid matrix inside the cell </li></ul><ul><li>At this point life diverges into two forms and two pathways </li></ul><ul><ul><li>Anaerobic cellular respiration (aka fermentation) </li></ul></ul><ul><ul><li>Aerobic cellular respiration </li></ul></ul>
  13. 16. Cellular Respiration Reactions <ul><li>Glycolysis </li></ul><ul><ul><li>Series of reactions which break the 6-carbon glucose molecule down into two 3-carbon molecules called pyruvate </li></ul></ul><ul><ul><li>Process is an ancient one- all organisms from simple bacteria to humans perform it the same way </li></ul></ul><ul><ul><li>Yields 2 ATP molecules for every one glucose molecule broken down </li></ul></ul><ul><ul><li>Yields 2 NADH per glucose molecule </li></ul></ul>
  14. 18. Anaerobic Cellular Respiration <ul><li>Some organisms thrive in environments with little or no oxygen </li></ul><ul><ul><li>Marshes, bogs, gut of animals, sewage treatment ponds </li></ul></ul><ul><li>No oxygen used= ‘an’aerobic </li></ul><ul><li>Results 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. </li></ul><ul><li>End products such as ethanol and CO 2 (single cell fungi (yeast) in beer/bread) or lactic acid (muscle cells) </li></ul>
  15. 20. Aerobic Cellular Respiration <ul><li>Oxygen required=aerobic </li></ul><ul><li>2 more sets of reactions which occur in a specialized structure within the cell called the mitochondria </li></ul><ul><ul><li>1. Kreb’s Cycle </li></ul></ul><ul><ul><li>2. Electron Transport Chain </li></ul></ul>
  16. 21. Kreb’s Cycle <ul><li>Completes the breakdown of glucose </li></ul><ul><ul><li>Takes the pyruvate (3-carbons) and breaks it down, the carbon and oxygen atoms end up in CO 2 and H 2 O </li></ul></ul><ul><ul><li>Hydrogens and electrons are stripped and loaded onto NAD + and FAD to produce NADH and FADH2 </li></ul></ul><ul><li>Production of only 2 more ATP but loads up the coenzymes with H + and electrons which move to the 3 rd stage </li></ul>