Cellular Respiration

• Cellular Respiration 


  The process in which organisms take molecules broken down from food and release the chemical energy stored in the chemical bonds of those molecules.
• Cellular Respiration


  It’s important to remember that food is not the direct source of energy.
• The energy that is released from chemical bonds during cellular respiration is stored in molecules of ATP.
• Autotrophs


  Only undergoes photosynthesis
• Heterotrophs and Autotrophs


  Undergo cellular respiration
• Any food (organic) molecule, or nutrient, including carbohydrates, fats/lipids, and proteins can be processed and broken down as a source of energy to produce ATP.
• ATP will release energy for cellular metabolic processes.
• Cellular Respiration Simple Equation

  Nutrients + Oxygen → Water + Energy (ATP) + Carbon Dioxide
• Cellular Respiration Equation

  _C6H12O6 +_O2  →  _CO2 + _H2O + energy
• Cellular Respiration is a biochemical pathway just like photosynthesis in which each step (chemical reaction) of the process is dependent on the products of the previous step.
• Cellular respiration is a process that is aerobic.
• Some steps within the process of cellular respiration do not require the presence of oxygen and are therefore anaerobic.
• Cellular respiration takes place in the mitochondria of the eukaryotic cell.
• Recall that the mitochondria is considered to be the “powerhouse” of the cell because it produces the majority of a cell’s ATP.
• Parts of the Mitochondria

  • Inner Membrane
  • Outer Membrane
  • Cristae
  • Matrix
• Mitochondria has a double membrane.
• Energy Carriers Found in Cellular Respiration

  • ATP
  • NADH
  • FADH2
• Cellular respiration breaks down into these major steps.

  1. Glycolysis (anaerobic)
  2. Krebs Cycle (aerobic)
  3. Electron Transport Chain (aerobic)
• Glycolysis is an anaerobic step in the cellular respiration pathway.
• Glycolysis takes place in the cytoplasm of the cell and is a series of reaction using enzymes.
• Glycolysis is the splitting of a molecule of glucose.
• The products of glycolysis are broken down in the mitochondria to make more ATP.
• Products of Glycolysis

  • When a molecule of glucose is split, 2 pyruvate molecules, 2 NADH molecules, and 4 ATP are produced.
  • Glycolysis makes 4 molecules of ATP but it takes 2 molecules of ATP for the reaction to occur.  Therefore Glycolysis yields a net of 2 ATP molecules.
• Pyruvic acid is the main goal of glycolysis.
• Pyruvic Acid : Krebs Cycle
• NADH : ETC
• ATP : Usable Energy
• What Happens After Glycolysis?

  If O2 is not present : Fermentation

  If O2 is present : Krebs Cycle
• Pre-Krebs Cycle

  Before pyruvic acid enters the Krebs Cycle, it combines with an enzyme called Coenzyme A (CoA). This reaction produces a molecule of Acetyl CoA.
• Pre-Krebs Cycle

  Acetyl CoA is a molecule produced by almost all nutrients (carb., protein, lipids) before entering the Krebs cycle.
• Pathway to the Krebs Cycle

  Glycolysis → Pyruvic Acid → Acetyl CoA → Krebs Cycle
• Krebs Cycle

  • Cyclical series of oxidation reactions that give off CO2 and produce one ATP per cycle.
  • Requires Oxygen (Aerobic).
  • Turns twice per glucose molecule (produces 1 ATP per turn).
  • Produces two ATP.
  • Takes place in matrix of mitochondria.
• Krebs Cycle

  • Acetyl CoA (formed from Pyruvic Acid) combines with a four-carbon molecule to make a molecule of citric acid.2, , ATP.
  • Citric acid is broken down in several steps providing the energy to make NADH, FADH2, , ATP.
• Krebs Cycle Product Summary

  2 ATP → Usable energy

  6 NADH → Goes to ETC

  2 FADH2 → Goes to ETC

  CO2 → Byproduct
• Electron Transport Chain


  Series of proteins located in the mitochondrial membrane.
• Electron Transport Chain

  • Uses high energy electrons from the NADH and FADH2 provided  by the Krebs Cycle to move H+(protons) across the concentration gradient.
  • These protons pass back down the concentration gradient through ATP synthase to form ATP.  Very much like the ETC in the light reactions of photosynthesis.
• Electron Transport Chain

  Oxygen is used as the final electron acceptor at the end of the ETC.
• Electron Transport Chain

  Oxygen receives electrons and H+(hydrogen ions) and produces a molecule of water.
• ETC Product Summary

  34 ATP → Usable energy

  H2O → Byproduct
• Cellular Respiration ATP Tally

  Glycolysis : 2 ATP

  Krebs Cycle : 2 ATP

  ETC : 34 ATP