Ch6

Introduction

• Overview of kinetic and potential energy in biological systems.

Energy Concepts

Kinetic Energy

• Definition:

  • Energy of motion; associated with the movement of particles in a substance.

  • Contributes to heat energy and entropy.

Potential Energy

• Definition:

  • Stored energy or energy in a state of rest.

  • Examples: chemical energy, potential energy stored in the bonds of molecules.

Entropy

• Definition:

  • Measure of disorder in a system, symbolized as ( S ).

  • Higher entropy indicates a system is more disorganized.

Laws of Thermodynamics

First Law of Thermodynamics

• Concept: Conservation of energy.

  • Energy cannot be created or destroyed; it can only change forms.

Second Law of Thermodynamics

• Concept: Energy conversions are not 100% efficient.

  • Typically, they increase the entropy of the universe.

  • Illustrates the concept that systems naturally progress towards disorder.

• Implications for biological systems: Living organisms require continuous energy input to maintain order and stay alive, thereby illustrating the application of the 2nd law.

Caloric Measurement

• Definition of Calorie:

  • The amount of energy required to raise the temperature of 1 gram of water by 1°C.

• Food Calorie (Kilocalorie):

  • Denoted as kcal; equivalent to 1000 calories.

Adenosine Triphosphate (ATP)

• Definition:

  • ATP is known as the energy currency of the cell.

  • Function: Stores and transfers energy.

• Mechanism of Action:

  • Energy is released when a cell breaks the bond of the last phosphate group, resulting in adenosine diphosphate (ADP) plus a free phosphate.

• Importance: The released energy is utilized for cellular work.

Metabolism

Definition:

• The total of all chemical reactions in an organism.

Types of Metabolic Reactions:

1. Catabolic Reactions

   • Definition: Reactions that release energy by breaking down biomolecules.

   • Example: Cellular respiration, where glucose is oxidized into carbon dioxide.

2. Anabolic Reactions

   • Definition: Reactions that consume energy to build biomolecules such as polymers.

   • Example: Photosynthesis, where carbon dioxide and water are used to form glucose.

Enzymes

Definition:

• Proteins that catalyze chemical reactions in cells.

Activation Energy:

• Definition:

  • The initial energy needed to start a chemical reaction.

  • Enzymes lower this energy barrier, making reactions occur more easily.

Mechanism of Enzymes:

• Enzymes hold substrates in the correct position, thereby stabilizing them and reducing the energy required to initiate reactions.

Enzyme Structure:

• Shape of enzyme is critical due to the presence of an active site that fits a specific substrate, akin to a lock and key.

• If the shape of the enzyme is altered, the substrate may not fit, resulting in ineffective catalysis.

Enzyme Inhibitors

Examples of Inhibitors:

1. Disulfiram:

   • Used for treatment of alcoholism; inhibits enzyme activity.

2. Cyanide:

   • Inhibits cellular respiration by blocking enzymatic action.

3. Fluoride:

   • Inhibits glycolysis by affecting enzymes involved in metabolic pathways.

Oxidation and Reduction (Redox Reactions)

Definitions:

• Oxidation: Loss of electrons in a chemical reaction.

• Reduction: Gain of electrons in a chemical reaction.

• Mnemonic: OIL RIG (Oxidation Is Loss, Reduction Is Gain).

Examples:

• Oxidation: In cellular respiration, glucose is oxidized to carbon dioxide.

• Reduction: Oxygen is reduced to water during the process of cellular respiration.

Properties of Enzymes