Metabolism-Respiration

Keyword:Biol120Metabolism-Respiration

Topics

• Glycolysis
• Cellular Respiration
  • Citric Acid Cycle
  • Electron Transport System
  • Chemosmotic Phosphorylation
• Alternative Pathways
  • Lactic Acid Fermentation
  • Alcohol Fermentation

Energy and metabolism: Heterotrophy

Photosynthesis results in the storage of free energy into glucose and other sugars

This energy released via glycolysis ("glucose-breaking") and cellular respiration

Both pathways involve the controlled release of the free energy in the storage compound via enzymatically controlled reactions
Minimizes the losses of energy to heat for efficiency and cell integrity purposes
Glycolysis

• can take place without the presence of oxygen (anaerobic)
• occurs in the cytoplasm of cells
• requires specific enzymes to catalyze reactions

Pathway








































Cellular Respiration

• Aerobic process
• Takes place in the mitochondria
  
  
  
  
  
  

Three stages of cellular respiration

• Stage One: Citric Acid Cycle (Krebs cycle)(CAC)

  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  Summary: The two molecules of pyruvate from glycolysis give 2 ATPs, 8 NADHs and 2 FADH2
  Glycolysis + CAC=4 ATP, 10 NADH, 2 FADH2

Alternative metabolites

• proteins
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
• lipids
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  

Stage Two: Electron Transport System (ETS)-electron carriers are embedded in the membranes of the mitochondria

Stage Three: Chemosmotic Phosphorylation

Summary: Glycolysis (2) + CAC (2) + ETS (32)= 36 ATPs
38 ATPs - 2 ATPs invested in glycolysis= 34 ATPs net

Efficiency of this process










































Alternative pathways

In aerobic reactions, pyruvate produced by glycolysis passed through CAC

Under anaerobic conditions, pyruvate may follow two different pathways for further processing and energy harvesting

Lactic acid Fermentation (LAF) pathway-present in most organisms

Alcohol Fermentation (AF) pathway-a specialty of the yeasts/some bacteria

LAF














































AF
















































Keyword:Biol120Metabolism-Respiration

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Last Modified: Sept. 4, 1995
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Western Kentucky University.