Energy The coupling of anabolic and catabolic pathways catalyzed by enzymes, otherwise known as “Metabolism”

Metabolism and thermodynamics Metabolism includes all chemical reactions in an organism Pathways are a sequence of ordered steps each controlled by an enzyme Catabolic pathways release energy and typically hydrolyze molecules Anabolic pathways require energy and usually synthesize molecules

Forms of Energy Kinetic- energy of motion Thermal energy or heat is the measure of kinetic energy Potential- energy of position or location, stored Chemical energy is potential energy stored in bonds of molecules

Thermodynamics 1st law- the total energy of the universe is constant, it can only be transferred and transformed from one kind to another. 2nd law- energy transfer or transformation results in increasing disorder or entropy. Energy is often lost as heat during a reaction or motion of matter (friction)

Reactions An exergonic reaction proceeds with a net release of free energy and is spontaneous An endergonic reaction is nonspontaneous and must absorb free energy from the surroundings ATP powers cellular work by coupling exergonic and endergonic reactions

Energy coupling: using exergonic reactions to power endergonic ones ATP or adenosine triphosphate can be hydrolyzed to ADP and an inorganic phosphate molecule releasing ~ 13kcal/mol. The phosphate is often transferred to another molecule in a process called phosphorylation This molecule is more reactive (less stable) ex. Integral transport protein in the membrane A cell regenerates the ATP during cellular respiration

The Hydrolysis of ATP to ADP + P

Enzymes are Catalyst Enzymes speed up chemical reactions by lowering the EA, activation energy. Remember Enzymes are proteins and have very specific shapes. They fit with the substrate(s) at the active site. The result in an “induced fit” that creates the enzyme-substrate complex.

Enzyme Substrate Complex

Activation Energy EA EA The red line indicates the reaction with an enzyme.

Optimal temp and pH Table: pH for Optimum Activity Enzyme pH Optimum Lipase (pancreas)8.0 Lipase (stomach)4.0 - 5.0 Lipase (castor oil)4.7 Pepsin1.5 - 1.6 Trypsin7.8 - 8.7 Urease7.0 Invertase4.5 Maltase6.1 - 6.8 Amylase (pancreas)6.7 - 7.0 Amylase (malt)4.6 - 5.2 Catalase7.0

Enzyme activity Proteins are denatured at high temp, and low or high pH, this is why buffers are so important to the maintenance of chemical reactions. The rate of a reaction can be controlled or regulated in 3 ways Denaturing- interupts the 3D shape Competitve inhibitors- compete for active site Noncompetitive inhibitors- attach at allosteric site

Inhibitors

Enzyme helpers Cofactors- nonprotein helpers for catalytic activity, bind to either the enzyme or the substrate ex. Zinc, iron, and copper Coenzymes- are organic helpers and include most vitamins http://academic.brooklyn.cuny.edu/biology/bio4fv/page/coenzy_.htm