Thermodynamics. Physical Thermodynamics. Physical process in the biological process in the biological

membranes.membranes.

Heat and ThermodynamicsHeat and Thermodynamics

First Law of ThermodynamicsFirst Law of Thermodynamics

Second Law of Thermodynamics Second Law of Thermodynamics

EntropyEntropy

Adiabatic ProcessAdiabatic Process

Heat Engine CycleHeat Engine Cycle

EnthalpyEnthalpy

First Law of ThermodynamicsFirst Law of ThermodynamicsThe first law of thermodynamics is the application of the The first law of thermodynamics is the application of the

conservation of energyconservation of energy principle to heat and principle to heat and thermodynamic processes:thermodynamic processes:

The first law makes use of the key The first law makes use of the key concepts of concepts of internal energy, heatinternal energy, heat , , and and system worksystem work. It is used . It is used extensively in the discussion of extensively in the discussion of heat enginesheat engines ..

System WorkSystem WorkWhenWhen workwork is done by a thermodynamic is done by a thermodynamic system, it is ususlly a gas that is doing system, it is ususlly a gas that is doing the work. The work done by a gas at the work. The work done by a gas at constant pressure is: constant pressure is:

For non-constant pressure, the work can be For non-constant pressure, the work can be visualized as the area under the pressure-volume visualized as the area under the pressure-volume curve which represents the process taking place. curve which represents the process taking place. The more general expression for work done is:The more general expression for work done is:

Work done by a system decreases the internal Work done by a system decreases the internal energyof the system, as indicated in the energyof the system, as indicated in the First First Law of ThermodynamicsLaw of Thermodynamics. System work is a . System work is a major focus in the discussion of heat engines.major focus in the discussion of heat engines.

Second Law of Second Law of ThermodynamicsThermodynamics

The second law of thermodynamics is The second law of thermodynamics is a general principle which places a general principle which places constraints upon the direction of heatconstraints upon the direction of heat transfertransfer and the attainable efficiencies and the attainable efficiencies of heat enginesof heat engines . In so doing, it goes . In so doing, it goes beyond the limitations imposed by the beyond the limitations imposed by the first law of thermodynamics. It's first law of thermodynamics. It's implications may be visualized in terms implications may be visualized in terms of the waterfall analogy. of the waterfall analogy.

Second Law: Heat EnginesSecond Law: Heat EnginesSecond Law of Thermodynamics: It is Second Law of Thermodynamics: It is impossible to extract an amount of impossible to extract an amount of heat QH from a hot reservoir and use it heat QH from a hot reservoir and use it all to do work W . Some amount of heat all to do work W . Some amount of heat QC must be exhausted to a cold QC must be exhausted to a cold reservoir. This precludes a perfect heat reservoir. This precludes a perfect heat engineengine . . This is sometimes called the "first This is sometimes called the "first form" of the second law, and is form" of the second law, and is referred to as the Kelvin-Planck referred to as the Kelvin-Planck statement of the second lawstatement of the second law. .

Second Law: RefrigeratorSecond Law: RefrigeratorSecond Law of Thermodynamics: It is not Second Law of Thermodynamics: It is not possible for heatpossible for heat to flow from a colder to flow from a colder body to a warmer body without any workbody to a warmer body without any work having been done to accomplish this flow. having been done to accomplish this flow. Energy will not flow spontaneously from a Energy will not flow spontaneously from a low temperaturelow temperature object to a higher object to a higher temperature object. This precludes a temperature object. This precludes a perfect refrigeratorperfect refrigerator . The statements about . The statements about refrigerators apply to air conditioners and refrigerators apply to air conditioners and heat pumpsheat pumps , which embody the same , which embody the same principles.principles.

EntropyEntropy

Second Law of Thermodynamics: In Second Law of Thermodynamics: In any cyclic process the entropy will any cyclic process the entropy will either increase or remain the same. either increase or remain the same. EntropyEntropy : a state variable whose : a state variable whose change is defined for a reversible change is defined for a reversible process at T where Q is the heat process at T where Q is the heat absorbed. absorbed.

Entropy:a measure of the amount Entropy:a measure of the amount of energy which is unavailable to of energy which is unavailable to do work.do work.

EntropyEntropy :a measure of the disorder :a measure of the disorder of a system. Entropyof a system. Entropy :a measure of :a measure of the multiplicity of a system. the multiplicity of a system.

Entropy in Terms of Heat and Entropy in Terms of Heat and TemperatureTemperatureThe macroscopic relationship The macroscopic relationship which was originally used to which was originally used to define entropy S isdefine entropy S isdS = Q/TdS = Q/TThis is often a sufficient definition This is often a sufficient definition of entropy if you don't need to of entropy if you don't need to know about the microscopic know about the microscopic details. details.

Since entropy gives information Since entropy gives information about the evolution of an isolated about the evolution of an isolated system with time, it is said to give system with time, it is said to give us the direction of "time's arrowus the direction of "time's arrow " . " . If snapshots of a system at two If snapshots of a system at two different times shows one state different times shows one state which is more disordered, then it which is more disordered, then it could be implied that this state could be implied that this state came later in time. For an isolated came later in time. For an isolated system, the natural course of system, the natural course of events takes the system to a more events takes the system to a more disordered (higher entropy) state. disordered (higher entropy) state.

Alternative statements: Second Alternative statements: Second Law of ThermodynamicsLaw of Thermodynamics

Biological systems are highly Biological systems are highly ordered; how does that square ordered; how does that square with entropy?with entropy?

Adiabatic ProcessAdiabatic ProcessAn adiabatic process is one in which An adiabatic process is one in which no heat is gained or lost by the system. no heat is gained or lost by the system. The first law ofThe first law of thermodynamics with thermodynamics with Q=0 shows that all the change in Q=0 shows that all the change in internal energyinternal energy is in the form of work is in the form of work done. This puts a constraint on the done. This puts a constraint on the heat engine process leading to the heat engine process leading to the adiabaticadiabatic conditioncondition shown below. This shown below. This condition can be used to derive the condition can be used to derive the expression for the work done during an expression for the work done during an adiabatic process. adiabatic process.

The ratio of the specific heats g = The ratio of the specific heats g = CP/CV is a factor in determining the CP/CV is a factor in determining the speed of soundspeed of sound in a gas and other in a gas and other adiabatic processes as well as this adiabatic processes as well as this application to heat engines. This application to heat engines. This ratio g = 1.66 for an ideal ratio g = 1.66 for an ideal monoatomic gas and g = 1.4 for air, monoatomic gas and g = 1.4 for air, which is predominantly a diatomic which is predominantly a diatomic gas.gas.

Heat TransferHeat Transfer

The transfer of heat is normally from a The transfer of heat is normally from a high temperature object to a lower high temperature object to a lower temperature object. Heat transfer temperature object. Heat transfer changes the internal energy of both changes the internal energy of both systems involved according to the First systems involved according to the First Law of Thermodynamics.Law of Thermodynamics.

Heat ConductionHeat Conduction Conduction is heat transfer by means of Conduction is heat transfer by means of molecular agitation within a material without molecular agitation within a material without any motion of the material as a whole. If one any motion of the material as a whole. If one end of a metal rod is at a higher end of a metal rod is at a higher temperature, then energy will be transferred temperature, then energy will be transferred down the rod toward the colder end down the rod toward the colder end because the higher speed particles will because the higher speed particles will collide with the slower ones with a net collide with the slower ones with a net transfer of energy to the slower ones. For transfer of energy to the slower ones. For heat transfer between two plane surfaces, heat transfer between two plane surfaces, such as heat loss through the wall of a such as heat loss through the wall of a house, the rate of conduction heat transfer house, the rate of conduction heat transfer is:is:

QQ = heat transferred = heat transferred in time = in time = tt

TT = thermal = thermal conductivity of the conductivity of the barrierbarrier

AA = area = area

d d = thickness of = thickness of barrierbarrier

Heat ConvectionHeat Convection Convection is heat transfer by mass Convection is heat transfer by mass motion of a fluid such as air or water motion of a fluid such as air or water when the heated fluid is caused to when the heated fluid is caused to move away from the source of heat, move away from the source of heat, carrying energy with it. Convection carrying energy with it. Convection above a hot surface occurs because above a hot surface occurs because hot air expands, becomes less hot air expands, becomes less dense, and rises (see Ideal Gas Law). dense, and rises (see Ideal Gas Law).

Hot water is likewise less dense than Hot water is likewise less dense than cold water and rises, causing cold water and rises, causing convection currents which transport convection currents which transport energy. Convection is thought to energy. Convection is thought to play a major role in transporting play a major role in transporting energy from the center of the Sun to energy from the center of the Sun to the surface, and in movements of the surface, and in movements of the hot magma beneath the surface the hot magma beneath the surface of the earthof the earth

It is difficult to quantify the effects of It is difficult to quantify the effects of convection since it inherently depends convection since it inherently depends upon small nonuniformities in an upon small nonuniformities in an otherwise fairly homogeneous medium. otherwise fairly homogeneous medium. In modeling things like the cooling of In modeling things like the cooling of the human body, we usually just lump the human body, we usually just lump it in with conductioit in with conductio

Heat EnginesHeat Engines

A heat engine typically uses energy A heat engine typically uses energy provided in the form of heat to do work provided in the form of heat to do work and then exhausts the heat which and then exhausts the heat which cannot be used to do work. cannot be used to do work. Thermodynamics is the study of the Thermodynamics is the study of the relationships between heat and work. relationships between heat and work. The first law and second law of The first law and second law of thermodynamics constrain the thermodynamics constrain the operation of a heat engine. operation of a heat engine.

The first law is the application of The first law is the application of conservation of energy to the conservation of energy to the system, and the second sets limits system, and the second sets limits on the possible efficiency of the on the possible efficiency of the machine and determines the machine and determines the direction of energy flow.direction of energy flow.

EnthalpyEnthalpy

Four quantities called Four quantities called "thermodynamic potentials" are useful "thermodynamic potentials" are useful in the chemical thermodynamics of in the chemical thermodynamics of reactions and non-cyclic processes. reactions and non-cyclic processes. They are internal energy, the enthalpy, They are internal energy, the enthalpy, the Helmholtz free energy and the the Helmholtz free energy and the Gibbs free energy. Enthalpy is defined Gibbs free energy. Enthalpy is defined byby H = U + PV

where P and V are the pressure and where P and V are the pressure and volume, and U is internal energy. volume, and U is internal energy. Enthalpy is then a precisely Enthalpy is then a precisely measurable state variable, since it is measurable state variable, since it is defined in terms of three other defined in terms of three other precisely definable state variables. It is precisely definable state variables. It is somewhat parallel to the first law of somewhat parallel to the first law of thermodynamics fora constant thermodynamics fora constant pressure systempressure system

Q = DU + PDV Q = DU + PDV since in this case Q=DHsince in this case Q=DH

It is a useful quantity for tracking It is a useful quantity for tracking chemical reactions. If as a result of an chemical reactions. If as a result of an exothermic reaction some energy is exothermic reaction some energy is released to a system, it has to show up released to a system, it has to show up in some measurable form in terms of in some measurable form in terms of the state variables. An increase in the the state variables. An increase in the enthalpy H = U + PV might be enthalpy H = U + PV might be associated with an increase in internal associated with an increase in internal energy which could be measured by energy which could be measured by calorimetry, or with work done by the calorimetry, or with work done by the system, or a combination of the two. system, or a combination of the two.

The internal energy U might be thought of The internal energy U might be thought of as the energy required to create a system in as the energy required to create a system in the absence of changes in temperature or the absence of changes in temperature or volume. But if the process changes the volume. But if the process changes the volume, as in a chemical reaction which volume, as in a chemical reaction which produces a gaseous product, then work produces a gaseous product, then work must be done to produce the change in must be done to produce the change in volume. For a constant pressure process volume. For a constant pressure process the work you must do to produce a volume the work you must do to produce a volume change DV is PDV. Then the term PV can be change DV is PDV. Then the term PV can be interpreted as the work you must do to interpreted as the work you must do to "create room" for the system if you presume "create room" for the system if you presume it started at zero volume.it started at zero volume.

MembraneMembrane. . Mechanism of Mechanism of transport charge and non transport charge and non

charge partial throw membrane charge partial throw membrane structure of cell.structure of cell.

Transfer of water soluble molecules across cell membranes by transport proteins

Two classes of membran proteins

Comparison of passive and active transport

Examples of sbubstances transported across cellmembranes by carrier proteins

Bacteriorhodopsin: A carrier protein

Conformational change in protein to passivelycarry glucose

Two components of an electrochemical gradient

Three ways of driving active transport

Three types of transport by carrier proteins

Two types of glucose carriers for transfer of glucoseacross the gut lining

The Na-K pump

The Na-K pumpcycle

Osmosis

Avoiding osmotic swelling

Carrier mediated solute transport in animal and plant cells

The structure of an ion channel

Patch-clamp recording

Current through a single ion channel

Gated ion channels

Stress activated ion channels allow us to hear

Distribution of ions gives rise to membranepotential

K+ is responsible for generating a membrane potential

Nernst equation: V = 62log10(Co/Ci)

Neurons

Action Potenetial

Three conformations of the voltage gated Na channel

----------

+++++ +++++

Ion Flows and the Action Ion Flows and the Action PotentialPotential

The propogation of an action potential along an axon

The Action PotentialThe Action Potential

SynapsesSynapses

SynapsesSynapses

SynapsesSynapses

Excitatory vs. Inhibitory Excitatory vs. Inhibitory SynapseSynapse

SynapsesSynapses

Ion ChannelsIon Channels