Lecture #7 Introduction to Metabolism & Enzymes

Energy the capacity to cause change the ability to do work Kinetic Energy Thermal energy Potential Energy

Thermodynamics The study of energy transformations that occur Law #1 – Energy can neither be created nor destroyed; it can only be transferred and transformed

Chemical Potential Energy A + B ↔ C + D The potential energy available for release in a chemical reaction Potential energy - stored energy that can be used to transfer energy from one system to another

G and  G Gibbs free energy - the energy portion of a system available to do work – when temperature and pressure are constant  G – the change in free energy that happens when a system changes  G = G end – G start

What  G means …. A + B ↔ C + D  if  G is negative – the ending free energy is lower than the starting free energy  therefore, there has been a release of energy – energy must have been transferred or transformed – spontaneous reaction  If  G is positive – the ending free energy is higher than the starting free energy  Energy is absorbed by the system - non- spontaneous reaction

Exergonic reaction »energy is released »the  G value is less than 0 (negative) »spontaneous »the  G value represents the theoretical maximum amount of work (quantity of energy that can be transferred to another system) Endergonic reaction »energy is absorbed and stored »the  G value is grater than 0 (positive) »non-spontaneous »the  G value represents the amount of energy required to drive the reaction

Respiration/Photosynthesis C 6 H 12 O 6 + O 2 ↔ 6CO 2 + 6H 2 O forward reaction:  G = -686 kcal/mol reverse reaction:  G = 686 kcal/mol

Equilibrium balance when a chemical reaction proceeds at the same rate as its reverse reaction, with no change in the amount of each compound lowest possible free energy (G) value a system in balance cannot spontaneously change Must push the system away from the balance

Equilibrium in Metabolism? C 6 H 12 O 6 + O 2 → 6CO 2 + 6H 2 O CO 2 O2O2 C 6 H 12 O 6 CO 2 O2O2 C 6 H 12 O 6 C 6 H 12 O 6 + O 2 → 6CO 2 + 6H 2 O

ATP ADP P PiPi  G=-7.3 kcal/mol

Ca 2+ -ATPase – skeletal muscle CYTOPLASM ER LUMEN Ca 2+ ATP Ca 2+ P

Enzymes a protein catalyst catalyst – speeds up a chemical reaction

E + S ↔ ES ↔ E + P

Continued tomorrow and in today’s lab session……..