Photosynthesis and Cellular Respiration

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Photosynthesis and Cellular Respiration
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Energy and Life

• Energy the ability to do work
• Autotrophs use sunlight, CO2 , and water to
• make their own food (sugars) ? PHOTOSYNTHESIS
• Heterotrophs cant make their own food, they
  have to eat autotrophs to stay alive!

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ATP

• ATP (Adenosine Tri-Phosphate) the energy storage
  molecule used by most organisms
• It is the usable version of a cells energy
• ATP gets broken down to release energy in the
  Mitochondria

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Photosynthesis

• CO2 H2O Sunlight -----------? C6H12O6 O2
• Chlorophyll pigment inside the chloroplast that
  absorbs sunlight
• Light Reactions Convert light energy to ATP
  (during the day)
• Dark Reactions Convert CO2 H2O to sugars (at
  night)

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Light Reactions

• Light Reactions (Photophosphorylation) Convert
  light energy to ATP (during the day) takes the
  energy in light and the electrons in water to
  make the energy rich molecules ATP and NADPH
• H20 ADP Pi NADP light ? ATP NADPH
  O2 H

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Dark Reactions

• Dark Reactions (Calvin Benson Cycle) Convert
  CO2 H2O to sugars (at night) takes CO2 from
  the atmosphere and the energy in ATP NADPH to
  create a glucose molecule.
• 6CO218ATP12NADPH H ?18ADP18 Pi 12NADP 1
  glucose

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Cellular Respiration

• C6H12O6 O2 -----------? CO2 H2O Energy
• The breakdown of food molecules to release energy
  needed for work.
• Step 1 Glycolysis converts glucose (6-carbon
  sugar) to pyruvate (2, 3-carbon sugars)
  releases energy ? 2 ATP
• Step 2 Aerobic Respiration breakdown of
  Pyruvate in the presence of Oxygen ? NO ATP made!
• Step 3 Krebs Cycle Produces coenzymes (NADH)
  to speed up the last step ? 2 ATP
• Step 4 Electron Transport Chain Uses the
  coenzymes (NADH) to crank out mass amounts of ATP
  ? 32 ATP!

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Total ATP Production

• CELLULAR RESPIRATION PRODUCES A TOTAL OF 36 ATP
  MOLECULES!

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Anaerobic Respiration Chemical reactions that
release the energy from foods in the absence of
oxygen (O2)

• Cells (active muscle cells) or organisms
  (bacteria, yeast) that use this process to get
  their energy needs live on the small amount of
  ATP that is provided by Glycolysis (2 ATP)

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Anaerobic Respiration

• Alcoholic Fermentation Converts pyruvate
  (3-carbon sugar) to CO2 and ethanol (alcohol)
• Bakers use the fermentation of yeast cells to
  make breads ( the CO2 makes the dough rise)
• Also used industrially in the manufacturing of
  beer wine
• Ethanol is added to gasoline to make gasohol

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Anaerobic Respiration

• Lactic Acid Fermentation converts pyruvate to
  Lactic Acid
• During strenuous exercise you deplete your
  muscle cells of oxygen so they enter the
  anaerobic cycle
• Lactic acid is a waste product produced from
  this
• Lactic acid build up in the muscles causes
  muscle cramping
• Lactic acid made in the muscles diffuses into
  the bloodstream , then goes to the liver, where
  it is converted back into pyruvate

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Aerobic vs. Anaerobic

• Aerobic vs. Anaerobic Respiration
• 1. Oxygen required 1. No Oxygen required
• 2. Produces 36 ATP 2. Produces 2 ATP
• ATP provided through the complete Aerobic
  breakdown of glucose provides energy for
  activities such as eating, sleeping, exercising,
  STUDYING BIOLOGY!
• Aerobic Respiration is relatively inefficient !!
  ? 36 ATP is only about half the energy contained
  in a glucose molecule!

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• Question Where does the rest of the energy go?
• Answer Lost as heat

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Organelles where these events occur...

• Photosynthesis Occurs in the Chloroplasts
• Both the Light and Dark reactions
• Stroma fluid inside chloroplast (Dark
  reactions)
• Thylakoids individual membrane layer
  (pancake) (Light reactions)
• Granum (Grana) an entire stack of thylakoids

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• Cellular Respiration Occurs in the
  Mitochondria, Cytoplasm
• Glycolysis occurs in the cytoplasm, products
  get shipped to the Mitochondria
• Aerobic Respiration Krebs Cycle occurs in the
  Mitochondria Matrix
• Electron Transport Chain occurs on the Cristae

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Enzymes Catalysts
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Key Terms

• Catalyst A chemical agent that accelerates a
  chemical reaction without being permanently
  changed in the process
• Enzyme A protein molecule that acts as a
  Biological Catalyst
• Substrate the molecule that the enzyme binds
  to the molecule that undergoes the reaction

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5 Things All Enzymes Have in Common

• 1. They dont make anything happen that could
  not happen on its own
• 2. They are NOT permanently altered or used up
  by a reaction (they are re-used)
• 3. The same enzyme usually works for the forward
  and reverse directions of a reaction
• 4. All enzymes work on specific substrates
• 5. Enzymes function to lower the Activation
  Energy of a chemical reaction

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Activation Energy

• Activation Energy The extra energy required to
  destabilize existing chemical bonds and initiate
  a chemical reaction
• Enzymes increase the rate of reactions by
  lowering the Activation Energy!

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• Active Site Pocket on the enzyme in which the
  substrate binds to forming an Enzyme-Substrate
  Complex (lock and key)
• Products what the substrate is turned into
  after binding to the enzyme gets released

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Factors That Affect Enzyme Activity

• 1. Temperature rate increases with temp.
  increase only until the temperature optimum is
  reached maximizes random molecular movement
• Optimal temp range for most human enzymes
  35-40? C (94-99? F )
• 2. pH pH optimum pH 4 to 6 pepsin (a
  digestive enzyme) works best at pH 2

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Factors That Affect Enzyme Activity

• 3. Ionic Concentration high ion concentrations
  (salt) slow down enzyme activity
• 4. Cofactors Coenzymes presence of small
  non-protein molecules required for proper enzyme
  catalysis
• Cofactors inorganic (Zn, Cu, metals)
• Coenzymes organic (vitamins)

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Factors That Affect Enzyme Activity

• 5. Enzyme Inhibitors substance that binds to
  an enzyme and decreases its activity
• Competitive Inhibition resemble an enzymes
  normal substrate, compete with it for the active
  site, block it
• Noncompetitive Inhibition binds to another
  part of the enzyme besides the active site
  causes the enzyme to change shape so the active
  site cant bind to the substrate
• 6. Allosteric Regulation receptor site on some
  part of the enzyme other than the active site
  serve as a chemical on/off switch
  (activator/inhibitor)
• 7. Feedback Inhibition the product of one
  metabolic pathway can become the inhibitor for
  another

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