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

2. 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

3. 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

4. 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)

5. 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

6. 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

7. The Hydrolysis of ATP to ADP + P

8. 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.

9. Enzyme Substrate Complex

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

11. Optimal temp and pH Table: pH for Optimum Activity Enzyme pH Optimum
Lipase (pancreas)8.0
Lipase (stomach)
Lipase (castor oil)4.7
Pepsin
Trypsin
Urease7.0
Invertase4.5
Maltase
Amylase (pancreas)
Amylase (malt)
Catalase7.0

12. 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

13. Inhibitors

14. 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