Ch' 5 Metabolic Functions

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Ch. 5 Metabolic Functions

• Energy Metabolism
• Sum of all chemical reactions within a cell
• Adenosine Triphosphate (ATP)
• Enzymes
• Central Metabolic Pathways
• Glycolysis
• Fermentation
• Respiration

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Metabolic scheme
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Adenosine triphosphate (ATP)
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Enzymes

• Enzymes are Catalysts
• Lower the activation energy of a reaction
• Substrate
• Product
• Specific active sites or catalytic sites
• Serve as cofactors and coenzymes
• Most enzymes are proteins

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Enzyme active site
Figure 6.10
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Cofactor
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The metabolic pathway
Figure 6.5
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Central metabolic pathway
Figure 6.9
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Glycolysis (Embden Meyerhoff pathway)

• Multi step breakdown of glucose into two
  pyruvic acid molecules
• Precursor to other metabolic pathways
• Generates a small amount of ATP
• 2 net ATP molecules (produces 4 ATP molecules but
  need 2 ATPs to start glycolysis)
• Generates reducing power - NADH
• Electron-carrier molecule

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Glycolysis
Figure 6.15
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Pentose phosphate pathway

• Primarily responsible for generating 5 carbon
  sugars used in the biosynthesis of DNA and RNA
• Generates reducing power - NADPH

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Respiration

• Electron carriers (reducing power) generate a
  proton gradient or proton motive force (pmf)
• PMF generates energy (oxidative phosphorylation)
• Pyruvic acid enters into the tricarboxylic acid
  cycle (TCA) a.k.a. Krebs cycle
• Electron transport chain
• Aerobic respiration - oxygen is the final
  electron acceptor
• Anaerobic respiration - inorganic molecule is the
  final electron acceptor

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TCA cycle
Figure 6.16
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Electron transport chain (E. coli)
Figure 6.19
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Aerobic respiration - Energy yield
Figure 6.21
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Fermentation (eg. of anaerobic resp.)

• Only ATP generated is through glycolysis
• No oxidative - phosphorylation
• NADH is oxidized to NAD
• Organic molecule is the final electron acceptor
  (s/a pyruvate and acetaldehydes)
• A diversity of end products produced (i.e. lactic
  acid, alcohols, etc.)

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Final electron acceptor - fermentation
Figure 6.22
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Fermentation pathways