Cell & Molecular Bio Chap 5.1

1. Metabolic Pathways and Networks

• Definition: Metabolic pathways consist of a series of chemical reactions within a cell, each catalyzed by a specific enzyme.

• Interconnected Networks: These pathways do not function in isolation but are interconnected, forming a complex metabolic network.

• Regulation: Cells regulate these pathways to maintain homeostasis and meet energy demands.

2. Oxidation and Reduction in Metabolism

• Oxidation: The loss of electrons from a molecule.

• Reduction: The gain of electrons by a molecule.

• Importance: Oxidation-reduction (redox) reactions are fundamental to energy transformations in cells, enabling the controlled release of energy.

3. Energy Generation Through Oxidation of Organic Molecules

• Cells extract energy by breaking down organic molecules, primarily carbohydrates, lipids, and proteins.

• This oxidation process releases energy, which is harnessed in the form of ATP.

4. Glycolysis: The First Step of Energy Harvesting

• Definition: Glycolysis is the breakdown of glucose (C6H12O6) into two molecules of pyruvate.

• Location: Occurs in the cytoplasm of the cell.

• ATP Production: Produces a small net gain of ATP.

• NADH Generation: High-energy electrons are transferred to NAD+, forming NADH.

5. Connecting Glycolysis to the Citric Acid Cycle (TCA Cycle)

• Pyruvate from glycolysis enters the mitochondria and is converted into acetyl-CoA.

• Acetyl-CoA enters the TCA cycle (Krebs cycle), leading to further oxidation of carbon molecules.

6. Free Energy Change (∆G) in Glucose Oxidation & High-Energy Electron Carriers

• ∆G (Gibbs Free Energy Change): Determines whether a reaction will proceed spontaneously.

• Glucose Oxidation: Releases large amounts of energy, stored in electron carriers like NADH and FADH2.

7. Major High-Energy Electron Carriers

• NADH (Nicotinamide Adenine Dinucleotide)

• FADH2 (Flavin Adenine Dinucleotide)

• These molecules temporarily store energy and transfer electrons to the electron transport chain (ETC).

8. Oxidative Phosphorylation: The Final Step of Energy Production

• Occurs in the mitochondria.

• Uses the Electron Transport Chain (ETC) to pass electrons through protein complexes.

• Produces ATP via ATP synth