Energetics

Introduction to Energetics

Purpose: Introduces the importance of energy within living organisms.

Source: Information is sourced from Pearson Education, Inc.

Characteristics of Living Things

Life is defined by eight characteristics:

• Order: Structured organization at the molecular, cellular, and systemic levels that define biological functions.

• Reproduction: Ability to produce offspring, ensuring the continuation of species through sexual or asexual means.

• Inherited information base: Genetic material (DNA/RNA) that is passed through generations and encodes traits that influence an organism's structure and function.

• Growth and development: Increase in size and complexity over time, guided by genetic instructions and environmental factors.

• Energy utilization/processing: Using energy obtained from the environment to carry out various life processes, such as metabolism.

• Response to environment: Reacting to stimuli, encompassing a range of behaviors aimed at survival (e.g., movement towards food, escaping predators).

• Regulation/Homeostasis: Maintaining a stable internal environment despite changes occurring externally, achieved through regulatory mechanisms (e.g., temperature and pH balance).

• Evolutionary adaptation: Changes over time that enhance survival, often resulting in traits that improve fitness in a particular environment through natural selection.

Energy Is Central to Life

Requirement of Energy

• All living things require energy for various life processes, including growth, reproduction, and maintenance of metabolic functions.

Ultimate Energy Source

• The sun is identified as the primary source of energy for most organisms, with a few exceptions (e.g., deep-sea hydrothermal vent communities that rely on chemosynthesis).

Photosynthesis

• Energy from the sun is captured by photosynthetic organisms (e.g., plants, algae) and converted into chemical energy stored in glucose. This process involves chlorophyll and occurs in chloroplasts, producing oxygen as a byproduct.

The Nature of Energy

Definition of Energy

• Defined as the capacity to cause movement against an opposing force or the capacity to perform work. Energy exists in various forms, and its transformations are fundamental to biological systems.

Types of Energy

• Potential Energy: Stored energy, often related to the position of an object or the arrangement of molecules (e.g., chemical bonds).

• Kinetic Energy: Energy in motion, which can manifest in various forms such as thermal energy or mechanical energy.

Thermodynamics

The study of energy transitions is defined as thermodynamics.

• Laws of Thermodynamics: Fundamental principles governing energy.

  • First Law: Energy is neither created nor destroyed, only transformed.

  • Second Law: Energy transfer always leads to greater disorder (increased entropy), implying that energy transformations are not 100% efficient.

• Entropy: A measure of disorder; higher entropy indicates higher disorder within a system. In isolated systems, entropy tends to increase over time.

Energy Transformation

• During energy transformations, some energy is lost as heat, considered the most disordered form of energy.

  • Example: In a car engine, only a portion of energy from gasoline combustion propels the car; the rest dissipates as heat, demonstrating the inefficiency of energy use.

Energy Use by Living Things

• Organisms utilize energy for various life functions: Order, Reproduction, Growth, Energy processing, Response, Regulation. While living organisms can create local increases in order through metabolic processes, they rely on energy to do so.

Macromolecular Synthesis

• Organisms can synthesize complex, ordered molecules (like starches and proteins) from simpler, less ordered molecules (like simple sugars and amino acids). This synthesis process, which includes pathways like gluconeogenesis and protein synthesis, requires energy input.

Endergonic and Exergonic Reactions

• Endergonic Reactions: Reactions that absorb energy, where the products contain more energy than the reactants, often occurring in anabolic pathways.

• Exergonic Reactions: Reactions that release energy, where the products contain less energy than the reactants, typically found in catabolic pathways.

• Coupled Reactions: Exergonic reactions can power endergonic reactions, enabling energy transfer within biological processes, allowing cells to perform work.

The Energy Dispenser: ATP

• Adenosine Triphosphate (ATP): The primary energy transfer molecule in living organisms. ATP is often called the "energy currency" of the cell due to its role in energy transfer.

• Energy from Food: In animals, energy obtained from food is converted into ATP through cellular respiration, which drives metabolic processes such as muscle contraction and nerve transmission.

• Structure of ATP: Contains three negatively charged phosphate groups that repel each other, providing high-energy bonds. Breaking these bonds releases energy that can be harnessed for cellular work.

The ATP/ADP Cycle

• ATP donates its third phosphate group to drive chemical reactions, converting to adenosine diphosphate (ADP) in the process. To regenerate ATP, ADP must acquire a phosphate group through cellular respiration or photophosphorylation, completing the cycle continuously in living systems.

Enzymes and the Activation Barrier

• Enzymes are catalysts that reduce the activation energy needed for chemical reactions, enabling reactions to occur more readily at physiological temperatures.

  • Example of Enzyme Action: The presence of an enzyme (like lactase) lowers the energy barrier for the splitting of lactose into glucose and galactose, resulting in total energy release, significantly enhancing metabolic efficiency.