Introduction to Biophysics

Introduction to Biophysics/Life and its Physical Basis

• Biophysics is a branch of science applying physical principles and methods to biological problems.
• It bridges the gap between physics and biology, providing a physical perspective on life.
• The course aims to define the scope of biophysics, describe life from a physical perspective, explain the mechanism of energy acquisition in organisms, and trace energy origins.

Learning Outcomes

• Students will define the scope of biophysics.
• Students will describe life from a physical viewpoint.
• Students will describe how organisms acquire energy and its origins.

Outline

• What is Biophysics?
  • Biophysics is the bridging science.
  • Scope of biophysics includes data analysis and structure, computer modeling, molecules in motion, neuroscience, bioengineering/nanotechnology/biomaterials, and medical applications.
• Life: Its Characteristics
  • Life exhibits characteristics such as order, sensitivity, regulation, reproduction, growth, and development, homeostasis, and energy processing.
• Life: Thermodynamic Features
  • Life is an open system interacting with its surroundings.
  • Living organisms are capable of doing work and organizing themselves.
  • They require energy to maintain organization and function.
• Thermodynamics: Development and its Laws
  • Thermodynamics deals with the interaction of heat and other forms of energy.
  • Laws of thermodynamics govern energy exchanges in living organisms.
• Free Energy Change
  • Free energy is the energy available to do work under cellular conditions.
  • Free energy change (ΔG) is a measure of the spontaneity of a biological process, influenced by enthalpy (ΔH) and entropy (ΔS).
• Enthalpy and Entropy
  • Enthalpy is the total heat content of a system at constant pressure.
  • Entropy measures the level of disorder in a system.

Scope of Biophysics

• Data analysis and structure.
• Computer modeling.
• Molecules in motion.
• Neuroscience.
• Bioengineering, nanotechnology, and biomaterials.
• Medical applications.

Life: A Physical Perspective

• Life is an open system.
• It involves the interactions between a system and its surroundings.
• Key features of life from a physical perspective include: order, sensitivity, regulation, reproduction, growth, development, homeostasis, and energy processing.

Life: Its Characteristics

• Order: Organized structure
• Sensitivity: Responds to stimuli.
• Regulation: Internal adjustments.
• Reproduction: Creates offspring.
• Growth: Increases in size.
• Development: Changes in form or function across the lifespan.
• Homeostasis: Maintains stable internal conditions.
• Energy processing: Acquires and uses energy.

Life: Thermodynamic Features

• Organisms are open systems exchanging matter and energy with their environment.
• Organisms are capable of doing work and self-organization.
• Maintaining order and functioning requires a constant supply of energy.

Thermodynamics: Its Relation to Organisms

• Thermodynamics describes interactions among energy forms.
• It elucidates conversions of thermal energy and its impact on matter.
• Living creatures adhere to the laws of thermodynamics.

Development of Thermodynamics

• Historical developments like the steam engine led to the advancement of thermodynamic principles.
• Early inventors (Savery, Newcomen, and Watt) contributed to these advancements.

Forms of Energy

• Organisms use various energy forms.
• Potential energy (stored energy, determined by height)
• Kinetic energy (energy of motion).

1st Law of Thermodynamics

• Energy can be transferred or transformed, but not created or destroyed.
• Heat flow influences a system.
• Work occurs when a system acts on its surroundings.

State Functions

• A state function depends only on the initial and final states, not the path taken.
• Internal energy is a state function.
• State functions (e.g., internal energy, enthalpy), are measurable quantities.

Zeroth Law of Thermodynamics

• Two bodies in thermal equilibrium with a third are in thermal equilibrium with each other.
• This helps define the concept of temperature.
• Temperature is a measure related to the "hotness" of a system.

Example of Energy Conversion

• Energy in foods gets converted to kinetic energy (e.g., cheetah running).

2nd Law of Thermodynamics

• Heat flow is never completely converted to work in real processes.
• Entropy (measure of disorder) always increases in spontaneous processes for an isolated system.

Equilibrium and the Second Law

• Equilibrium is a state where spontaneous change is impossible.
• Entropy is maximal at equilibrium.

Free Energy Change

• Free energy is the energy available to a system to do work under cellular conditions.
• The change in free energy (ΔG) during a biological process depends on enthalpy and entropy changes.

Enthalpy: Changing Variables

• Enthalpy is a system's total heat content at constant pressure.
• Enthalpy is related to internal energy, pressure, and volume.

Entropy

• Entropy is a measure of disorder in a thermodynamic system.
• In a given isolated system, spontaneous processes tend to increase entropy.

Differences Between Enthalpy and Entropy

• Enthalpy (denoted by H) measures the total heat content of a system at constant pressure.
• Entropy (denoted by S) measures the level of disorder in a system.
• They are different characteristics/properties.

Free Energy, Stability, and Equilibrium

• Organisms live at the expense of free energy.
• Free energy decreases in spontaneous processes and the stability of a system increases.

Conclusion

• Mechanisms of energy acquisition among organisms are crucial for existence.