BiologicalThermodynamics 1
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Title Page
Biophysics Dept. UMF C. Davila 2018
Course: Biological Thermodynamics
Instructors: Dr. Adrian Iftime, Dr. Eva Katona, Dr. Anca Popescu, Dr. Octavian Călinescu, Dr. Ramona Babeș
Module: Series 1, English, 2022/2023, 1st semester
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Outline
General Concepts
1st Principle of Thermodynamics – Applications in Biology
2nd Principle of Thermodynamics – Applications in Biology
Thermodynamic Potentials
Thermodynamic Gradients and Fluxes
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General Concepts
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General Concepts
Definition: Thermodynamics is derived from Greek
thermos = hot
dynamis = power, movement
Scope: Describes the relationship between heat and movement (energy transformations)
Focus: Studies reciprocal transformations of different energy forms in natural systems.
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What is Temperature?
Indicates continuous disordered movement at the atomic and molecular level:
Molecules in a gas or liquid are in motion
Molecules in a solid have less movement
Reference: Animated .gif files provide visual examples.
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What is Temperature?
Temperature descriptions:
“Cold” = slow molecular motion
“Hot” = faster molecular motion
Reference: Further animated .gif illustrations available.
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What is Temperature?
Temperature relates to kinetic energy of atoms/molecules:
Types of motion: translation, rotation, oscillation
Temperature applicable to systems with many atoms.
Absolute zero (0 K or -273.15 °C) marks the point with no molecular movement.
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Temperature Scales
Kelvin Scale: 0 K = no random molecular movement, corresponds to -273.15 °C
The Kelvin and Celsius scales vary identically.
Homework: Convert 100 K to Celsius and find the freezing temperature of water in Kelvin.
Note: "Degree Kelvin" is incorrect, temperatures at or below 0 K are impossible.
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Temperature Scales Importance
Clear distinction between temperature scales is crucial to avoid confusion.
Body temperature: ~37°C is ~98.6°F.
In scientific contexts, Kelvin is generally required (e.g., ideal gas law).
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What is Pressure?
Pressure involves converting disordered molecular movement into useful ordered movement.
Definition: Pressure = measure of molecular force over wall surface.
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Terminology in Thermodynamics
Use specialized terms to avoid confusion with other scientific fields
a) Thermodynamic systems
b) State parameters
c) Thermodynamic processes
d) Equilibrium state
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Thermodynamic Systems
Definition: Macroscopic systems consisting of many atoms/molecules, in continuous random motion and energetic interactions.
They have defined boundaries separating them from the surroundings.
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Classification of Thermodynamic Systems
Types of boundaries:
Adiabatic walls (ideal insulator)
Examples include thermos bottles and living organisms.
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State Parameters
Definition:
Describes the current situation of the system (e.g., temperature, volume).
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State Parameters
Measurable Quantities Include:
Temperature (K)
Pressure (N/m²)
Density (kg/m³)
Concentration (mol/L)
Mass (kg)
Volume (m³)
Number of Moles (mol)
Divided into intensive and extensive parameters.
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Relationships Between State Parameters
Foundational relationships:
p – pressure of the gas
V – volume
– number of moles
R – universal gas constant (R = 8.31 J/mol·K)
T - temperature
Equation: pV = RT (Fundamental law of gases applicable in particle systems in thermal motion).
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Effects of Parameter Changes
If one state parameter changes while another remains constant, specific observations occur:
If V is constant and T increases → pressure increases due to more force from moving particles.
If T is constant and V increases → pressure decreases because the same force distributes over a larger area.
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Thermodynamic Processes
Definition: Transitions of thermodynamic systems mediated by state parameter modifications.
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Equilibrium State in Thermodynamics
In the equilibrium state, state parameters remain constant over time and space, reflecting a system's natural tendency to seek equilibrium.
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The Necessity of Equilibrium
Humorously stated: A system in thermodynamic equilibrium has constant state parameters, which is undesirable for life!
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Reversible Processes
Characteristics:
Quasistatic processes that maintain thermodynamic equilibrium at every moment
System returns to initial state through the same pathway when conditions are reversed.
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Irreversible Processes
Characteristics:
Return to initial state occurs via different pathways, often due to external intervention.
Intermediate states typically not equilibrium states.
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Laws of Thermodynamics
Laws condense basic properties of nature and govern thermodynamic behavior.
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0th Principle of Thermodynamics
If two systems are in thermal equilibrium with a third system, they are in thermal equilibrium with each other.
Conclusion: Thermal equilibrium is transitive.
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1st Principle of Thermodynamics
Expression:
Energy cannot be created from nothing, nor can it be lost without trace; internal energy of an isolated system is conserved.
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Internal Energy
Definition: The total energy of all system components, comprised of:
Kinetic energy (translations, rotations, vibrations)
Potential energy (interactions between molecules, electric/magnetic force-field interactions).
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Conservation of Internal Energy
Evidence shows that internal energy of a perfectly isolated system does not change over time (i.e., it is conserved).
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Variation in Internal Energy
A system can receive energy from outside, indicating that the final internal energy can exceed the initial state. Variation (ΔU) only depends on the initial and final states, irrespective of intermediate pathways.
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Biological Application: Energy from Glucose
Living systems don’t burn glucose directly to avoid thermal damage.
Glucose stores internal energy through chemical bonds.
Direct burning releases energy as intense heat, which is damaging to cells.
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Handling Energy in Living Systems
Living systems process energy through smaller steps, releasing manageable energy increments via enzymatic reactions (e.g. ATP storage).
The total energy released is the same as direct burning but done more efficiently over several stages.
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Heat Absorption in Chemical Reactions
The heat absorbed or liberated in a reaction depends solely on initial and final reactant states—not intermediate stages.
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Numerical Expression of the 1st Principle
Goal: Express variation of internal energy mathematically (ΔU).
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Heat Transfer
Heat gained/lost is denoted by Q. Absorbed heat leads to an increase in internal energy.
Sign Convention: Q > 0 means the system receives heat.
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Relationship between Temperature and Energy
T = measure of average kinetic energy of molecules.
U = total energy of all molecules within the system.
Q = energy transfer resulting from temperature difference.
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Work and Internal Energy
Work (L) denotes energy transfer due to ordered motion.
Sign Convention: L > 0 means the system does work, leading to a reduction in internal energy.
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Net Change in Internal Energy
Equation: ΔU = Q - L
Describes net energy change in the system.
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Summary of the 1st Principle in Simple Terms
Energy is neither created nor destroyed but can transform between different forms (heat and work).
In an isolated system, internal energy remains conserved (ΔU = 0).
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Energy Transformations
Energy conservation persists during form transformations.
Example: Work converts to heat, which while occurring, increases the disordered molecular motion.
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Reminder on Work and Heat
Work done often results in heat generation through friction, signifying energy transformation.
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Heat Converted to Work
Heat can be converted into mechanical work; kinetic energy increases, causing movement.
Example: Gasoline engines convert heat from fuel combustion into mechanical energy.
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Internal Energy Conversion in Nuclear Reactions
Example:
Internal energy in nuclear reactions translates into heat during fission processes, subsequently generating work.
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ATP and Thermodynamics
ATP (adenosine tri-phosphate) serves as a crucial energy carrier in biological systems, storing energy efficiently for varied cellular functions.
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Measuring Energy
SI unit for energy = Joule (J)
Work = Force × Distance; relationship between Joules and Newtons.
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Defining Calorie and its Conversion
1 calorie is the energy to heat 1 g of water by 1°C.
Relationship: 1 cal ≈ 4.18 J.
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Calories in Human Energy Use
Medical energy calculations typically utilize kilocalories (kcal). 1 kcal = 1000 cal. Average energy expenditure for humans = 2000-5000 kcal daily.
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Calculating Food Energy
Total energy in food is calculated via bomb calorimetry:
Alternatively, use macronutrient energy formulas for carbohydrates, proteins, and fats.
Homework: Calculate energy from a 100 g chocolate bar containing 57 g carbs, 8 g protein, and 30 g fat.
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Energy Balance and Metabolism
Components: Energy from food, energy expended as work, and energy release as heat.
Relates to basal metabolic rate which influences diet.
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BMR Determination
Methods: Indirect calorimetry and other metabolic assessments evaluate caloric expenditure.
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Mifflin-St. Jeor Equation
Formula: BMR (kcal/day) = 10W + 6.25H – 5A + S, with W = weight, H = height, A = age, and S = gender specification.
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Energy Circulation in Bioenergetics
Visualize molecular pathways of energy utilization in cells, referencing reactions involving ADP + Pi to ATP.
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Energy Circulation in Living Systems
The sun serves as the net energy source for biosphere cycles, concerning plants and mitochondrial functions in providing ATP from organic compounds.
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Summary of the 1st Principle
Energy cannot be created or annihilated; it is conserved and must be accounted for at both consumption and utilization phases.
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2nd Principle of Thermodynamics
Principle of increasing entropy/disorder governing spontaneous processes in systems.
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Restrictions of Spontaneous Processes
Unidirectional process: Cannot spontaneously result in heat conversion into total work without energy input from external sources.
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Visualization of Entropy Increase
Illustrated using the movement of ink in water, demonstrating increasing entropy with thermal action.
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Characteristics of Spontaneous Processes
These processes are invariably accompanied by increases in disorder, expressed by entropy variations within systems.
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Entropy Variation with Temperature
Colder systems experience slower entropy increases compared to hotter systems due to molecular motion differences.
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Entropic Relationship with Heat and Temperature
For isolated systems, equation: ΔS = Q/T, relates entropic change with added heat and existing temperature.
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Entropy Increase in Spontaneous Processes
Spontaneous processes lead to free energy decrease and increased entropy, establishing a directional characteristic for system evolution over time.
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Definitions of Entropy
Defined from macroscopic and microscopic perspectives, with utmost focus on statistical probabilities and microstate arrangements within a system.
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Macroscopic Definition of Entropy
Entropy as a state function correlates to heat exchanged under reversible processes, introducing Clausius' relational equation with temperature.
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Microscopic Perspective on Entropy
An analogy using coin toss outcomes illustrates the probability variation with increasing arrangements and configurations at molecular levels, reflecting higher entropy likelihoods.
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Boltzmann's Entropy Formula
Formula: S = k ln W, where W is the thermodynamic probability of a system based on arrangements leading to disorder.
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Irreversible Transformation of Systems
Systems progress towards maximal entropy in time, representing spontaneity towards states of higher disorder unless external intervention occurs.
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Key Insights on Thermodynamic Processes
Each irreversible transformation accentuates entropy increments, tying thermodynamics intricately to biological processes and energy dynamics.
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Summary of Irreversible Processes
Distinction forms between energy-dissipating processes and their spontaneous developmental tendencies toward disorganization in thermodynamic systems.
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Lasting Outcomes of Thermodynamic Laws
The definitive conclusion: The laws underpinning thermodynamics emphasize conservation and directional principles governing energy conversions in biosystems.
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Biological Context of Thermodynamics
Examination of metabolic processes in living organisms reflecting coupled vs. uncoupled entropic tendencies; significant for understanding biological energy management.
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Evolution Toward Equilibrium
Systems evolve towards dynamic equilibrium, maintaining constant internal states through external energy contributions, fundamental to sustaining life processes.
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Summary of Key Thermodynamic Concepts
Energy flow, heat transfer, coupled processes, and entropy—all pivotal in biological functioning and sustaining life forms.
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Thermodynamic Potentials in Biology
Internal Energy (U) as the primary thermodynamic potential.
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Enthalpy and its Relevance
Definition: Enthalpy (H) measures heat exchanged in isobaric conditions.
Equation: H = U + pV
Applicable in biological reactions at constant pressure.
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Gibbs Free Energy and Biological Applications
Determines the spontaneous direction of reactions under isothermal and isobaric conditions, measuring effectiveness to perform work.
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Gradients and Fluxes
Explores diverse gradients impacting physical properties like temperature or concentration, propelling transport and thermodynamic principles in living systems.
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Flux Characteristics in Thermodynamics
Defines fluxes in relation to thermodynamic forces, emphasizing vector representations of distributions and their implications in biological dynamics.
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Summary of Energy Dynamics
Revisits core thermodynamic principles with a biological perspective, integrating foundational knowledge for comprehensive applications in biosystems.
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Final Remarks and Review
Urges ongoing engagement with thermodynamic principles as they provide an essential framework applicable across numerous scientific disciplines.