Chapter 9: Energy Production in Cells

Overview

• Two methods of ATP production:
  • Cellular respiration
  • Fermentation
• Cellular respiration produces significantly more ATP than fermentation.

ATP Production

• Forms of ATP: Adenosine Triphosphate (ATP)
  • Essential for all cells.

Cellular Respiration

1. Stages of Cellular Respiration:
   • Glycolysis
   • Pyruvate oxidation
   • Citric Acid Cycle (Krebs Cycle/TCA Cycle)
   • Electron Transport Chain (ETC)
2. Aerobic process
3. Produces ~36-38 ATP per glucose
4. Electron acceptor: Oxygen

Fermentation

1. Single Stage: Glycolysis
2. Anaerobic process
3. Produces only 2 ATP per glucose
4. Electron acceptors: Organic molecules other than oxygen

Oxidation and Reduction

• Oxidizing Glucose: Stealing energy from glucose
  • Glucose: Highly reduced (rich in energy)
  • Oxidation: Loss of electrons, loss of energy, loss of hydrogens
  • Reduction: Gain of electrons, gain of energy, gain of hydrogens

Tools and Terminology

• Substrate Level Phosphorylation: Produces ATP directly during glycolysis and Krebs cycle.
• Oxidative Phosphorylation: Produces ATP at the ETC.

Equations and Metabolic Pathways

• Cellular Respiration Equation:
  • Inputs: Glucose, Oxygen
  • Outputs: CO₂, Water, Heat, Light, ATP
• Photosynthesis (upcoming chapter): Opposite reaction to cellular respiration

Glycolysis

• Occurs in the cytoplasm
• Inputs: Glucose, ADP, Inorganic Phosphate, NAD+
• Outputs: 2 Pyruvate, 2 NADH, 2 ATP (net)
• ATP production method: Substrate Level Phosphorylation

Pyruvate Processing

• Occurs in the mitochondrial matrix
• Inputs: Pyruvate
• Outputs: 2 Acetyl CoA, 2 NADH, 2 CO₂

Citric Acid Cycle (Krebs Cycle/TCA Cycle)

• Occurs in the mitochondrial matrix
• Inputs: Acetyl CoA
• Outputs: 6 NADH, 2 FADH₂, 4 CO₂, 2 ATP (or GTP)
• ATP production method: Substrate Level Phosphorylation

Electron Transport Chain (ETC)

• Occurs in the inner mitochondrial membrane
• Produces most ATP via Oxidative Phosphorylation

Metabolic Pathways

• Catabolic Pathways: Break down molecules, release energy (ATP)
• Anabolic Pathways: Build larger molecules, require energy (ATP)

Regulation of Cellular Respiration

• Regulated steps: All steps of cellular respiration are regulated.

Importance of Homeostasis

• Stable conditions (homeostasis):
  • Examples: Body temperature, blood glucose levels
• Metabolism: All chemical reactions in a cell aimed at maintaining homeostasis

Study Tips for Chapter 9

• Memorization:
  • Know stages of cellular respiration
  • What goes in and what comes out at each stage
  • Locations of each stage in a eukaryotic cell
  • How and where ATP is produced in each stage