An Introduction to Metabolism (Chapter 8) – General Biology Study Notes

An Introduction to Metabolism

Overview

Metabolism encompasses all the chemical reactions that occur within a living organism, enabling it to maintain life, grow, and respond to environmental changes. These reactions are governed by the laws of thermodynamics and are organized into metabolic pathways.

Metabolism and Thermodynamics

Definition of Metabolism

• Metabolism is the totality of an organism’s chemical reactions.

• Chemical reactions occur when atoms, ions, or molecules collide in such a way that they produce a new substance.

Metabolic Pathways

• A metabolic pathway begins with a specific molecule and ends with a product.

• Each step in the pathway is catalyzed by a specific enzyme.

• Pathways can be linear, branched, or cyclic, depending on the sequence of reactions.

• Example: Glycolysis is a metabolic pathway that breaks down glucose to pyruvate.

Types of Energy

• Energy is the capacity to cause change or do work.

• Forms of energy relevant to biology include:

  • Kinetic energy: Energy of motion (e.g., movement of molecules).

  • Thermal energy: Energy associated with random movement of atoms or molecules; heat.

  • Potential energy: Stored energy due to position or structure (e.g., chemical bonds).

  • Chemical energy: Potential energy available for release in a chemical reaction.

• Energy can be converted from one form to another (e.g., chemical energy to kinetic energy).

The Laws of Thermodynamics

• First Law of Thermodynamics (Law of Conservation of Energy):

  • Energy can be transferred and transformed, but it cannot be created or destroyed.

• Second Law of Thermodynamics:

  • Every energy transfer or transformation increases the entropy (disorder) of the universe.

  • Some energy is always lost as heat, making it less available to do work.

• Application to Biology: Biological processes obey these laws; for example, cells transform energy during metabolism, increasing entropy in the environment.

Examples and Applications

• Climbing up a platform converts the kinetic energy of muscle movement to potential energy.

• Diving off the platform converts potential energy back to kinetic energy.

• Cells convert chemical energy from food into kinetic and thermal energy.

Additional info: Later sections (not shown in these images) would likely cover free energy, ATP, enzyme function, and regulation, as suggested by the table of contents and partial text.