Ch 7

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Ch 7
2010-10-17 20:00:03

Cellular recpiration
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  1. Oxidation
    • a substance that loses one or more electrons (and hydrogen atoms)to another is said to have undergone oxidation.
    • A substance that looses an electron is said to be oxidized
    • - and has acted as a reducing agent
    • If ATP get oxidized the energy is released and its said reduced to ADP
  2. Reduction
    • the gain of electrons and (hydrogen atoms)
    • A substance that gains electrons is reduced
    • - and has acted as oxidizing agent
  3. Redox reaction
    • the process by which electrons are transferred from one molecule to another
    • Hydrogen atom = Hydrogen ion plus electron
    • A substance oxidized - its electrons traveling energetically downhill
  4. Electron carriers
    • Molecules that serve to transfer electrons from one molecule to another in ATP formation.
    • Have the ability to oxidize or reduce other compounds by accepting or giving up hydrogen ions and electrons
    • 2 Electron carriers in Cellular respiration: NAD+ and FAD
  5. NAD+ Electron Carrier
    • Its positive charge indicates that it has one less electron than it does protons
    • •During a redoxreaction, NAD+ picks up one hydrogen atom and one single electron
    • NAD+ + electron -> NAD
    • NAD + hydrogen atom -> NADH
    • NAD+ empty state
    • NADH loaded state
  6. Cellular respiration
    • C6H12O6+ 6O2+ 36 ADP + 36P →6CO2+ 6H2O + 36 ATPThree main phases:
    • •Glycolysis - 2ATP
    • •The Krebs cycle - 2 ATP
    • •The Electron Transport Chain 34 ATP
    • Total net gain 36 ATP (2 ATP from glycolysis used up transporting 2 NADH produced into mitochondria)

    cellular respi - also called oxygen-dependent or aerobic energy transfer
  7. Glycolysis
    • •Occurs in the cytosol
    • •Does not require oxygen
    • •Is universally found in all organisms
    • •Yield per glucose molecule:
    • 2 ATP
    • 2 NADH
    • 2 molecules of pyruvic acid
  8. The pyruvic acid ( the transition step)
    • is a derivative of a glucose that was phosparilated( a phosphate groupd added from ATP) into glucose 6-phospate. The end products of glycolysis , glucose 6-phospate broken into 2 three carbon sugar molecules pyruvic acids.
    • Each paruvic acid combines with coenzyme A, forming acetyl CoA
    • acetyl CoA enters the Krebs cycle
    • 2 CO2 produced
    • 2 NADH produced
  9. Krebs cycle
    • This reaction occurs twice for each pyruvic acid
    • Acetyl CoA combines with oxaloacetic acid to produce citric acid.
    • •Occurs in the inner compartment of the mitochondria
    • •Two electron carriers(NAD+and FAD) are used
    • •Yield per glucose molecule:
    • –6 NADH
    • –2 FADH2
    • –2 ATP
    • - 4 CO2
  10. ETC
    • •Occurs inside the inner membrane of mitochondria
    • •Electrons are delivered by NADH and FADH2
    • •A series of protein carriers pass electrons from one to the other until the final receptor, O2, is reached
    • •As electrons are passed from carrier to carrier, energy is released and used to form ATP
  11. ETC 2
  12. •When NADH and FADH2 arrive at the inner membrane, they donate electrons to the first protein carrier
    • •Each protein carrier donates electrons to the next carrier in line
    • •Electrons keep moving because each carrier has a greater affinity for electrons than its uphill neighbor
    • •A series of redoxreactions occurs
    • Net gain 34 ATP
  13. ATP production
    • •As electrons pass through carrier proteins, the energy released is used to actively transport H+ions across the membrane (outer comparment in mitochondria)
    • •A hydrogen ion concentration gradient is established (Hydrogen pumped against its concentration gradient)
    • ATP synthase protein complexes use the potential energy in this concentration gradient to generate ATP from ADP
  14. The Role of Oxygen
    • Oxygen is the final acceptor of the electrons that move through the electron transport chain
    • •Oxygen has a great affinity for electrons and ‘pulls’ the electrons down the chain
    • •Oxygen atom + 2 electrons + 2H+= H20
    • •Electrons have to be removed from the transport chain in order for the process to continue
  15. Fermentation
  16. •When oxygen is not available, cells turn to fermentation
    • •During fermentation, the pyruvic acid formed by glycolysisis reduced to alcohol (and CO2) or an organic acid such as lactate
    • •This reaction is important because it uses NADH and regenerates NAD+, which keeps glycolysis going
  17. Alcoholic fermentation
    • •Fungi and some plants perform this anaerobic energy conversion
    • •When yeast grow in the absence of oxygen, they produce alcohol as a by-product of glycolysis
    • •Releases carbon dioxide
    • Pyruvic acids converted to acetaldehyde(later converted to alcohol) and it takes on electrons from NADH so NAD+ can be used again in glycolysis.
  18. Lactate Fermentation
    • •Animals and some bacteria perform this anaerobic energy conversion
    • •Pyruvic acid is converted to lactic acid
    • •Is a short-term means of supplying energy
    • •2 ATP are produced for each glucose molecule
    • Pyruvic acid accepts the electrons from NADH and becomes lactic acid
  19. Fermentation in Human Muscle Cells
    • •Muscle contractions require ATP
    • •When oxygen delivery to muscle cells cannot keep up with activity level, muscles must generate ATP through fermentation
    • •For brief periods of time, the body can produce a good deal of ATP just from glycolysis
    • •Their role is to supply enough energy to meet our needs until aerobic respiration can take over
    • Sore muscles - lactic build up
  20. Stored Energy
    • •Cells have the capacity to store small amounts of ATP and can stockpile a molecule called phosphocreatine(PCr)
    • •PCr acts as a reservoir of phosphate groups that can be used to produce ATP
    • •When a person first starts to exercise, the small reservoirs of ATP/PCr provide the energy
    • •After a few minutes, aerobic respiration provides most of the energy