How Cells Release Energy by pptfiles

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									    How Cells Release Energy
• Energy used to make
  ATP
• Cellular respiration
  processes
• Eukaryotic respiration
• Glycolysis
• Aerobic respiration
• Anaerobic respiration
• Photosynthesis and
  respiration
            Cellular Energy
• Cells use ATP for energy
• 3 ways to generate ATP
  – Aerobic respiration (most energy)
  – Anaerobic respiration
  – Fermentation
• Overall equation
  – C6H12O6 + 6O2  6CO2 + 6H2O + 30ATP
 Cellular Respiration Processes
• Glycolysis
  – Glucose (6C) split into 2 molecules of
    pyruvate (3C) + 2NADH and 2ATP
• Krebs cycle
  – Carbon released as CO2, energy transferred
    to ATP, NADH, and FADH2
• Electron transport
  – Electrons from NADH and FADH2 are used to
    generate ATP
       Eukaryotic Respiration
• In prokaryotic cells
  – Glycolysis occurs in cytoplasm
  – Krebs, ETC occurs in/around membranes in
    cytoplasm or cell membrane
• In eukaryotic cells
  – Glycolysis occurs in cytoplasm
  – Krebs, ETC occurs in mitochondrion
                Glycolysis
• 10 step process that splits glucose into 2
  molecules of pyruvate
• 2 molecules of ATP are needed to get the
  process started, but 4 are produced
  – Substrate level phosphorylation
• 2 NADH produced

• Net: 2 pyruvate, 2 ATP, 2 NADH
         Krebs Cycle Prep
• Pyruvate moved into mitochondrion, but
  not used directly in Krebs
• CO2 removed (NADH produced) when
  pyruvate converted to acetyl group
• Acetyl group bound to coenzyme A to form
  Acetyl CoA
             Krebs Cycle
• Acetyl group transferred from coenzyme A
  to oxaloacetate (4 C compound)
• 2C from acetyl group released as CO2,
  ATP, NADH and FADH2 produced
• 2 cycles of Krebs Cycle necessary for each
  glucose that enters glycolysis

• Net: 2 ATP, 6 NADH (+ 2 in prep), 2FADH2
Electron Transport Chain (ETC)
• ETC extracts potential energy in NADH
  and FADH2 (used to make ATP)
• Energy released in steps
  – As electrons passed, protons pumped from
    matrix to intermembrane space
• Proton gradient used to phosphorylate
  ATP
• Each NADH = 2.5 ATP
• Each FADH2 = 1.5 ATP
   Respiration Summary for Each
              Glucose
• Glycolysis
  – 4 ATP + 2 NADH – 2 ATP
• Krebs Cycle
  – 2 NADH (prep) + 2 ATP + 6 NADH + 2 FADH2
• ETC
  – 28 ATP – 2 ATP (NADH transport)
• Total: 30 ATP
What About Non-Glucose Foods?
      How Do Poisons Work?
• Krebs Inhibitors         • ETC inhibitors
  – Arsenic blocks           – Rotenone stops redox
    formation of acetyl        reactions early in ETC
    CoA                        (used by gardeners)
• Chemiosmosis               – Mercury inhibits ETC
  inhibitors                   similarly to rotenone
  – Insecticide DNP          – Cyanide and CO block
    makes cristae              transfer of electrons to
    permeable to protons       oxygen
        Non-Oxygen Options
• Anaerobic respiration
  – Alternative electron acceptor used
  – Nitrate, Sulfate, even CO2 can be used
  – Results in less ATP production
• Fermentation
  – Electrons from NADH produced in glycolysis
    used to reduce pyruvate
  – This recycles NAD+ for use in glycolysis
  – Alcohol or lactic acid fermentation possible
      Connections between
  Photosynthesis and Respiration
• Glycolysis probably the oldest of the
  reactions (common to nearly all living
  things)
• Photosynthesis probably evolved from
  glycolysis
• Once oxygen built up in the atmosphere,
  aerobic respiration became possible

								
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