General Biology Overview Course: General Biology 2 (BSB 102)

Instructor: T. Michael DodsonYear: 1976Course Code: 12081

Energy in Biological Systems

Definition of Energy:

Capacity to do work, existing in various forms such as thermal, chemical, and mechanical energy.

1st Law of Thermodynamics:

Energy cannot be created or destroyed, only changed in form. This principle underscores the conservation of energy in biological processes.

2nd Law of Thermodynamics:

Energy tends to flow from concentrated to less concentrated forms, which increases entropy. This law is critical in understanding how energy transformations lead to increased disorder within a system.

Work Done by Living Organisms

Living organisms transform potential energy (stored energy) into kinetic energy (energy of motion) to perform various biological functions. This transformation is essential for survival and activity.

ATP Functions:

Adenosine triphosphate (ATP) serves several vital functions:

• Protein synthesis: Provides the energy required for assembling amino acids into proteins.

• Muscle movement: Powers the contraction of muscles, enabling movement.

• Neural transmissions: Supplies energy for transmitting signals across neurons.

• Bioluminescence in lightning bugs for mating: ATP drives biochemical reactions that produce light in certain organisms, aiding in reproduction.

• Other cellular processes: Involved in activities such as cell division, transport of molecules across membranes, and other metabolic reactions.

Energy Conversion Efficiency

Conversion Efficiency: Only about 10% of the energy derived from food is utilized for building body mass and maintaining biological functions; the remainder is dissipated as heat during metabolic processes.Example: For instance, 10,000 pounds of corn and soybeans yield only about a 1,000-pound steer, illustrating the inefficiency of energy transfer in food webs.

Ecosystem Energy Flow

One-way Flow of Energy: Energy enters ecosystems primarily from the sun, where it is captured by producers (e.g., plants) and flows through various trophic levels, ultimately exiting as heat.Compensation for Energy Loss: Living organisms continuously capture and convert energy, balancing energy loss through metabolic processes.

Oxidation-Reduction Reactions

Redox Reactions: These reactions are critical for energy flow in biological systems:

• Oxidation: Involves the loss of electrons from a molecule.

• Reduction: Refers to the gain of electrons by another molecule.These reactions always occur in pairs; when one molecule loses an electron, another gains it through electron transfer via transport chains.

Photosynthesis and Cellular Respiration

Photosynthesis:

During photosynthesis, carbon dioxide (CO2) is reduced (gains electrons) to form glucose (C6H12O6), a key energy source for living organisms. This process is facilitated by sunlight and occurs in chloroplasts.

Cellular Respiration:

Oxidation of glucose during cellular respiration releases energy, which is captured in the bonds of ATP. This process occurs in multiple stages—glycolysis, the Krebs cycle, and the electron transport chain—allowing for efficient ATP production.

Chemical Reactions and Activation Energy

Reactions:

• Endergonic Reactions: Require energy input (anabolic processes) to synthesize larger molecules from smaller ones.

• Exergonic Reactions: Release energy (catabolic processes) by breaking down complex molecules into simpler ones.

Both reaction types require activation energy, the energy needed to initiate a reaction.

Enzymes:

Biological catalysts that lower the activation energy of chemical reactions, thereby increasing the rate at which reactions occur without being consumed in the process.

ATP: Energy Currency of the Cell

ATP Synthase:

A critical enzyme in the production of ATP for living organisms. It converts adenosine diphosphate (ADP) and inorganic phosphate (Pi) into ATP using energy derived from exergonic reactions, such as those occurring during cellular respiration.

Energy Transfer in ATP

Energy from exergonic reactions (e.g., glucose breakdown) is harnessed to synthesize ATP from ADP. When ATP releases a phosphate group to become ADP, energy is liberated, driving endergonic reactions such as protein synthesis and muscle contraction.

Energy Process Overview

Steps of Energy Flow:

1. Solar energy → Captured by photosynthesis in plants.

2. Photosynthesis → Converts sunlight into chemical energy stored in glucose.

3. Ingestion/Digestion → Organisms consume glucose and other organic compounds.

4. Cellular Respiration → Releases energy from glucose.

5. ATP → Energy currency used for various cellular activities.

6. Chemical Energy → Utilized in biological systems for growth, repair, and maintenance of life.