Introduction to Biochemistry: Thermodynamics Fundamentals
Topics Covered:
Thermodynamics
Energy
Work
Entropy
Enthalpy
Page 4: Overview of Thermodynamics
The term thermodynamics originates from the Greek words:
θέρμη (therme) meaning heat
δύναμις (dynamis) meaning power
Thermodynamics is the branch of science that studies the relationship between energy, work, and entropy.
Page 5: Importance and Nature of Energy
All living organisms depend on energy, primarily derived from food.
Essential functions supported by energy include:
Growth and repair
Sustaining life processes
Energy can exist in different forms and can be transformed from one form to another.
Energy transfer is crucial for driving biochemical processes.
Page 6-10: Forms of Energy
Types of Energy:
Electric energy
Heat energy from chemical reactions
Aeolic energy (wind energy)
Solar energy
Nuclear energy
Example:
Hiroshima (Japan, August 6, 1945), highlighting the destructive power of nuclear energy.
Page 13: Definition of Energy
Energy is defined as:
Lacking physical form
An intrinsic attribute of any substance or biological system
The capacity to do work.
The greater the energy possessed by an entity, the more capable it is of bringing about change.
Page 14-15: Understanding Energy's Properties
A fundamental property of energy is convertibility.
Examples of Energy Transformation:
Photosynthesis: Light energy is converted into chemical energy in plants.
Batteries: Chemical energy is transformed into light energy.
Page 18: Conservation of Energy Principle
Conservation of Energy: Energy cannot be created or destroyed; it can only be transformed from one form to another.
Examples:
Heating water in a kettle using electrical energy without depleting it.
Lighting a match transforms stored chemical energy into thermal energy.
Page 19: Forms of Energy
Kinetic Energy (KE)
Energy due to motion.
The faster an object moves, the more kinetic energy it possesses.
Example: A car moving at 70 mph has 3 times more kinetic energy than one moving at 40 mph.
KE depends on the mass of the object: KE = rac{1}{2} mv^2 where $m$ is mass and $v$ is velocity.
Potential Energy
Energy due to position or state.
Gravitational Potential Energy (GPE): Energy due to an object’s position relative to the earth.
Transformers into kinetic energy when released.
Page 20: Examples of Energetics
Kinetic Energy Explained:
A heavy object moving at a specific speed has more KE than a lighter object at the same speed.
Gravitational Potential Energy Explained:
Used in examples like hydroelectric dams, where stored water has GPE that can be converted to KE as it cascades down.
Page 24: Chemical Potential Energy
Energy within atoms bonded by covalent or ionic interactions.
Amount of energy needed to overcome these bonds, known as bond energy.
Examples of bond energies:
C-H bond: 412 kJ/mol
N-H bond: 390 kJ/mol
Stronger bonds require more energy to break.
Page 25: Scientific Definition of Energy
Energy is the capacity to do work.
Page 26: Work Defined
Work can be described as any process capable of lifting a weight.
Example: Lifting a book involves chemical energy converting to kinetic energy to overcome gravitational potential energy (GPE).
Page 27-28: Spontaneous vs. Non-Spontaneous Processes
Spontaneous Process:
Transfer of energy as heat from high temperature to low temperature without external energy input.
Non-Spontaneous Process:
Energy transfers from low temperature to high temperature, needing energy input.
Page 29-30: Understanding Entropy
Entropy derives from the Greek words indicating a 'turning towards.'
It describes the direction and likelihood of spontaneous changes.
Entropy has universal applications in thermodynamics.
Page 31-33: Entropy and Spontaneity
Entropy increases in spontaneous processes.
In spontaneous changes: Disorder increases, and entropy increases.
In non-spontaneous changes: Work is required to decrease entropy and achieve order.
Key Note: Non-spontaneous processes do not imply impossibility.
Page 37: Measuring Entropy
Entropy measures the distribution and dispersion of energy within a system.
Higher entropy indicates wider energy distribution and increased disorder.
Page 38: Reversing Entropy
Reversing entropy involves high-information work, often vital in biological systems.
Quote by Gilbert Newton Lewis: “Gain in entropy always means loss of information.”
Page 39: Energy Changes in Chemical Reactions
In chemical reactions, energy can be absorbed or released.
This is characterized as enthalpy change (ΔH), which encapsulates the energy changes associated with bond formation and breaking in reactions.
Page 40-44: Enthalpy Explained
Positive Enthalpy (Endothermic Reaction):
More energy is required to break original bonds than is released when forming new ones.
Energy is absorbed from the surroundings, indicating that heat input is required.
Negative Enthalpy (Exothermic Reaction):
More energy is released upon bond formation than is absorbed for bond breaking.
Energy is released into the surroundings, indicating that the reaction can proceed easily without added energy.
-Heat is considered a degenerate form of energy due to its inefficiency in producing work and its high entropy.
Page 45: Gibbs Free Energy (ΔG)
Gibbs Free Energy quantifies the interplay between entropy and enthalpy.
Formula:
riangle G = riangle H - T riangle S
Where:
( riangle G) is Gibbs free-energy change (kJ/mol)
( riangle H) is the change in enthalpy (kJ/mol)
(T) is temperature (Kelvin)
( riangle S) is the change in entropy (J/K·mol)
Page 46-47: Biological Applications of Gibbs Free Energy
In biological contexts, energy from spontaneous reactions (negative ΔG) can drive non-spontaneous (positive ΔG) reactions.
Cellular Respiration: A process where glucose (C₆H₁₂O₆) is consumed, releasing energy in a controlled manner through multiple reactions to yield ATP.
Example reaction for aerobic cellular respiration:
C₆H₁₂O₆ + 6O₂
ightarrow 6CO₂ + 6H₂O ext{ (ΔG = -2879 kJ/mol)}The energetics of metabolic processes involve coupling catabolic (energy-releasing) and anabolic (energy-consuming) reactions, thereby balancing cellular metabolism.
Page 48: Conclusion and Questions
The lecture concludes with a reflection on thermodynamic principles and their importance in biological systems.
Questions: Encouragement for students to engage and clarify concepts discussed during the lecture.