Energy and Metabolism: Foundations of Biology Study Notes

Energy and Metabolism

Introduction to Metabolism

Metabolism encompasses all chemical reactions occurring within an organism, enabling life processes such as growth, reproduction, and response to the environment. These reactions can either release or require energy.

• Metabolism: The sum of all chemical reactions in an organism.

• Exergonic reactions: Reactions that release energy.

• Endergonic reactions: Reactions that require energy input.

Metabolic Pathways

Metabolic pathways are sequences of chemical reactions, each catalyzed by a specific enzyme, that transform a starting molecule into a final product. Enzymes are crucial for the efficiency and specificity of these pathways.

• Metabolic pathway: A series of chemical reactions with a defined beginning and end.

• Enzymes: Proteins that act as biological catalysts, speeding up reactions without being consumed.

• Each enzyme is highly specific to its substrate and reaction.

• Example pathway: Starting molecule → (Enzyme 1) → Intermediate → (Enzyme 2) → Product

Types of Metabolic Pathways

Catabolism

Catabolic pathways break down complex molecules into simpler ones, releasing energy that can be used by the cell.

• Catabolic pathway: Reactions that release energy by breaking down molecules.

• Example: Cellular respiration – the breakdown of glucose in the presence of oxygen.

Anabolism

Anabolic pathways build complex molecules from simpler ones, requiring an input of energy.

• Anabolic pathway: Reactions that require energy to synthesize complex molecules.

• Example: Photosynthesis – the process that uses CO2, water, and light energy to build glucose.

Forms of Energy in Biology

Bioenergetics

Bioenergetics is the study of how organisms acquire, transform, and use energy to perform biological work.

• Energy: The capacity to cause change or do work.

• Forms of energy include:

  • Chemical energy (stored in bonds)

  • Light energy (from sunlight)

  • Heat energy (thermal energy)

Chemical Energy

Chemical energy is stored in the bonds of molecules and can be released during chemical reactions. This energy is a form of potential energy.

• Chemical energy: Energy based on molecular structure and bonds.

• Potential energy: Energy stored in chemical bonds, available for release in reactions.

• Energy is released when bonds are broken in exergonic reactions.

Potential vs. Kinetic Energy

Energy exists in two main forms: potential and kinetic. Potential energy is stored due to position or structure, while kinetic energy is associated with movement.

• Potential energy: Energy due to position or structure (e.g., chemical bonds, a diver on a platform).

• Kinetic energy: Energy of motion (e.g., movement of molecules, a diver in water).

• Example: Climbing up a platform converts kinetic energy (muscle movement) to potential energy; diving converts potential energy to kinetic energy.

Thermal Energy

Thermal energy is the energy associated with the random movement of atoms and molecules, often perceived as heat.

• Thermal energy: Energy from the movement of particles; transferred as heat between objects.

• Heat is a form of kinetic energy.

Summary Table: Types of Metabolic Pathways

Pathway Type	Energy Change	Example
Catabolic	Releases energy	Cellular respiration
Anabolic	Requires energy	Photosynthesis