Lecture 3 - Thermodynamics • Thermodynamics is the study...

Info iconThis preview shows pages 1–7. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Thermodynamics • Thermodynamics is the study of the effects of work, heat, and energy in a system • In the case of biological systems, thermodynamics refers to energy changes that occur during biochemical reactions • Typically, reactions that release energy are favored, whereas those that require energy are not • The hydrolysis of ATP to ADP plus P i results in the release of energy (30.5 kJ mol-1 ATP) • This ‘ released ’ energy can then be used to power (or drive) energetically unfavorable reactions p. 28 • The hydrolysis of ATP ( mixed anhydride/ester ) to form ADP plus P i is arguably the most important cellular biochemical reactions • This reaction releases energy (30.5 kJ mol-1 ATP = 7.3 kcal/mol ATP) The Hydrolysis of ATP to ADP plus P i Fig. 1-23, p. 29 Spontaneity in Biochemical Reactions • The most useful criterion for predicting the spontaneity of a reaction is the free energy , indicated by the symbol G (or Gibbs free energy ) • Not possible to measure absolute values of energy; instead we measure the changes in energy that occur during a process • Change in free energy is known as Δ G • For spontaneous, or energy-releasing, reactions Δ G is always a negative value - such a process is called exergonic • When the value of Δ G is positive, the process is non-spontaneous, or endergonic , meaning that energy must be supplied • For a process at equilibrium, with no net change in either direction, the change in free energy is zero ( Δ G = 0) How can we predict what reactions will occur in living cells? The Laws of Thermodynamics • The frst law oF thermodynamics is the law oF conservation oF energy - ‘ energy can neither be created nor destroyed but can be transformed from one form to another…. ’ • The second law oF thermodynamics: ‘ In a closed system, you can't Fnish any real physical process with as much useful energy as you had to start with - some is always wasted ’ • In other words, the second law states that 100% eFfciency is rarely possible • The two laws oF thermodynamics can be related to the Gibbs Free energy by the Following equation The use of thermodynamics in biology has a long history rich in confusion Δ G = Δ H - T Δ S The Laws of Thermodynamics • The frst law oF thermodynamics is the law oF conservation oF energy: for any physical or chemical change, the total amount of energy in the universe remains constant; energy may change form or it may be transported from one region to another, but it cannot be created or destroyed • The second law oF thermodynamics, which can be stated in several Forms, says that the universe always tends toward increasing disorder: in all natural processes, the entropy of the universe increases • Living organisms consist oF collections oF molecules much more highly organized than the surrounding materials From which they are synthesized, and organisms maintain and produce order, seemingly oblivious to the second law oF thermodynamics • But living organisms do not violate the second law; they operate strictly within it Gibbs Free Energy...
View Full Document

This note was uploaded on 02/05/2012 for the course BCH 311 taught by Professor Howlett during the Spring '08 term at Rhode Island.

Page1 / 31

Lecture 3 - Thermodynamics • Thermodynamics is the study...

This preview shows document pages 1 - 7. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online