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Biochemistry – Basic Concepts
Reaction, reactants and products
A + B →CWhat is a reactant?What is a product?IntermediatesReversible / irreversibleRate of reaction Rate constant
Energy related with reactions
Free energy diagramsExothermic and endothermic reactions
Laws of thermodynamics
Thermodynamics is the study of the effects of work, heat, and energy on a system
All of thermodynamics can be expressed in terms of four quantities Temperature (T) Internal Energy (G) Entropy (S) Heat / Enthalpy (H)
First law
Energy can be changed from one form to another, but it cannot be created or destroyed.
The total amount of energy and matter in the Universe remains constant, merely changing from one form to another.
The First Law of Thermodynamics (Conservation) states that energy is always conserved, it cannot be created or destroyed. In essence, energy can be converted from one form into another
ΔU = Q - W
Process terminology
Adiabatic – no heat transferredIsothermal – constant temperatureIsobaric – constant pressureIsochoric – constant volume
An adiabatic process transfers no heat therefore Q = 0
ΔU = Q – WWhen a system expands adiabatically, W is
positive (the system does work) so ΔU is negative.
When a system compresses adiabatically, W is negative (work is done on the system) so ΔU is positive
An isothermal process is a constant temperature process. Any heat flow into or out of the system must be slow enough to maintain thermal equilibrium
For ideal gases, if ΔT is zero, ΔU = 0Therefore, Q = W
Any energy entering the system (Q) must leave as work (W)
An isobaric process is a constant pressure process. ΔU, W, and Q are generally non-zero, but calculating the work done by an ideal gas is straightforward
W = P·ΔVWater boiling in a saucepan is an example of
an isobar process.
An isochoric process is a constant volume process. When the volume of a system doesn’t change, it will do no work on its surroundings. W = 0
ΔU = QHeating gas in a closed container is an
isochoric process
2nd law
"in all energy exchanges, if no energy enters or leaves the system, the potential energy of the state will always be less than that of the initial state."
This is also commonly referred to as entropy.
ΔG = ΔH – T ΔSG – Free energy / potential energy of the stateH – Enthalpy S – entropy / Disorder/ messiness