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Energy Production: Cellular Respiration Overview

Aug 18, 2024

Lecture on Bioenergetics: Cellular Respiration and Glycolysis

Overview

  • Focus: Breakdown of organic compounds to produce energy through cellular respiration.
  • Cellular Respiration: The opposite reaction of photosynthesis.
    • Photosynthesis: Converts CO2 and water into organic compounds and releases oxygen.
    • Respiration: Consumes glucose and oxygen, producing ATP, water, and CO2.

Phases of Cellular Respiration

  1. Glycolysis
    • Occurs in the cytosol (cytoplasm).
  2. Pyruvate Oxidation & Citric Acid Cycle
    • Occurs in the mitochondrial matrix.
  3. Oxidative Phosphorylation
    • Occurs on the mitochondrial inner membrane (electron transport chain).

Mitochondria Structure

  • Organelles of Cellular Respiration
    • Outer Membrane
    • Inner Membrane
    • Matrix

Glycolysis

  • Location: Cytosol
  • Steps: 10 enzyme-catalyzed steps

Two Phases of Glycolysis

  1. Energy-Requiring Phase (Endergonic)

    • Converts glucose (6 carbons) to two G3P molecules (3 carbons each).
    • Requires ATP hydrolysis (2 ATP used).

  2. Energy-Releasing Phase (Exergonic)

    • Converts two G3P to two pyruvate molecules.
    • Produces ATP (net gain of 2 ATP) and 2 NADH.

Detailed Steps of Glycolysis

Energy-Requiring Steps

  • Step 1:
    • Glucose phosphorylated to glucose-6-phosphate.
    • Enzyme: Hexokinase
    • ATP used.
  • Step 2:
    • Glucose-6-phosphate isomerized to fructose-6-phosphate.
    • Enzyme: Phosphoglucomutase
  • Step 3:
    • Fructose-6-phosphate to fructose-1,6-bisphosphate.
    • Enzyme: Kinase
    • ATP used.
  • Step 4:
    • Fructose-1,6-bisphosphate split into G3P and dihydroxyacetone phosphate.
    • Enzyme: Aldolase
  • Step 5:
    • Dihydroxyacetone phosphate converted to G3P.
    • Enzyme: Isomerase

Energy-Releasing Steps

  • Step 6:
    • G3P oxidized to 1,3-bisphosphoglycerate.
    • NAD+ reduced to NADH.
    • Enzyme: Dehydrogenase
  • Step 7:
    • 1,3-bisphosphoglycerate to 3-phosphoglycerate.
    • ATP produced via substrate-level phosphorylation.
    • Enzyme: Kinase
  • Step 8:
    • 3-phosphoglycerate converted to 2-phosphoglycerate.
    • Enzyme: Mutase
  • Step 9:
    • 2-phosphoglycerate to phosphoenolpyruvate (PEP).
    • Enzyme: Enolase
  • Step 10:
    • PEP to pyruvate.
    • ATP produced via substrate-level phosphorylation.
    • Enzyme: Kinase

Conclusion

  • End product of glycolysis: 2 pyruvate molecules, 2 net ATP, and 2 NADH.
  • Sets the stage for pyruvate oxidation and the citric acid cycle.

Next Topics

  • Pyruvate Oxidation
  • Citric Acid Cycle
  • Oxidative Phosphorylation

Full transcript