1. Chemical Reactions Review
Process that changes one set of chemicals into another
Bonds are broken and reforming
Reactant(s)  Product(s)
Energy is released or gained
Require activation energy

2. Chemical Reactions Review
Activation Energy: the minimum energy required to start a chemical reaction.
Energy Diagram:
Reaction peak
Reactants:
Products:

3. Energy in Reactions Endothermic Reaction Exothermic Reaction
Chem rxn that release energy will often occur spontaneously
Chem rxn. That absorb energy will not occur without a source of energy
exergonic reactions release energy
endergonic reactions consume energy

4. Catalysts
Substance that speeds up a chemical reaction by lowering energy barriers.
Biological Catalysts are called: ENZYMES
Activation energy represents the minimum amount of energy required in order for a process to occur. In chemical reactions, we can lower the activation energy of a reaction by using a catalyst. Catalysts initiate chemical reactions by lowering activation energy without being consumed or changed during the process. Enzymes are the biological catalysts, they speed up reactions by lowering the energy of activation required to initiate the reaction
Without enzymes, biochemical reactions could not proceed fast enough for life to be possible. Enzymes lower the energy required to start these reactions.

5. Enzymes
Are catalysts.
They speed up one type of chemical reactions that take place in cells.
They are substrate specific

6. Enzymes are Proteins Review: Proteins have 4 levels of organization
Elements: C, H, O, N
Monomer: Amino Acids
Polymer: Protein or Polypeptide
Proteins have 4 levels of organization

7. Four levels of organization
Primary Structure: order of the amino acids in the protein chain
Secondary Structure: the protein chain twisted or folded
Tertiary Structure: the chain folded
Quaternary Structure: clustering of multiple protein chains into the final three dimensional shape

8. Enzymes are Specific Enzymes catalyze only one chemical reaction
Enzymes are commonly named by adding a suffix "-ase" to the root name of the substrate molecule it acts on or job it does.
What are the following enzymes acting upon?
Lipase
Lactase
Sucrase
RNAase
hydrolase

9. Enzyme-substrate Complex: Induced Fit
Active Site
Reactants are known as substrates
Enzymes have a site where the substrates can be brought to react
The substrate binds to the active site of an enzyme
LOCK AND KEY - bit more complex than key analogy

10. Coenzymes and Cofactors
coenzymes are organic molecules that are required by certain enzymes to carry out catalysis.
They bind to the active site of the enzyme and participate in catalysis but are not considered substrates of the reaction. Thamine- Vitamin B1, Riboflavin- b2,
often classified as inorganic substances that are required for, or increase the rate of, catalysis. Zn, Fe, Mg, K

11. Ideal Working Conditions
Enzymes have an optimal temperature and pH range.
What temperature do enzymes work best in humans?
As the temperature rises, reacting molecules have more and more kinetic energy. This increases the chances of a successful collision and so the rate increases. There is a certain temperature at which an enzyme's catalytic activity is at its greatest (see graph). This optimal temperature is usually around human body temperature (37.5 oC) for the enzymes in human cells.
Above this temperature the enzyme structure begins to break down (denature) since at higher temperatures intra- and intermolecular bonds are broken as the enzyme molecules gain even more kinetic energy.
Each enzyme works within quite a small pH range. There is a pH at which its activity is greatest (the optimal pH). This is because changes in pH can make and break intra- and intermolecular bonds, changing the shape of the enzyme and, therefore, its effectiveness.

12. Enzyme Inhibitors
Inhibitors are molecules that prevent enzymes from working in their normal fashion
There are two types:
Nonspecific: Denatures enzymes
Temperature pH
Alcohol
Heavy Metals
Specific: Blocks or alters active sites.
Competitive
Noncompetitive
Poisons and drugs are examples of enzyme inhibitors.
Non-specific methods of inhibition include any physical or chemical changes which ultimately denatures the protein portion of the enzyme and are therefore irreversible.
A competitive inhibitor is any compound which closely resembles the chemical structure and molecular geometry of the substrate. The inhibitor competes for the same active site as the substrate molecule. The inhibitor may interact with the enzyme at the active site, but no reaction takes place. The inhibitor is "stuck" on the enzyme and prevents any substrate molecules from reacting with the enzyme. However, a competitive inhibition is usually reversible if sufficient substrate molecules are available to ultimately displace the inhibitor. Therefore, the amount of enzyme inhibition depends upon the inhibitor concentration, substrate concentration, and the relative affinities of the inhibitor and substrate for the active site.
Ethanol is metabolized in the body by oxidation to acetaldehyde, which is in turn further oxidized to acetic acid by aldehyde oxidase enzymes. Normally, the second reaction is rapid so that acetaldehyde does not accumulate in the body.
A drug, disulfiram (Antabuse) inhibits the aldehyde oxidase which causes the accumulation of acetaldehyde with subsequent unpleasant side-effects of nausea and vomiting. This drug is sometimes used to help people overcome the drinking habit.
A noncompetitive inhibitor is a substance that forms strong covalent bonds with an enzyme and consequently may not be displaced by the addition of excess substrate. Therefore, noncompetitive inhibition is irreversible. A noncompetitive inhibitor may be bonded at, near, or remote from the active site. In any case, the basic structure of the enzyme is modified to the degree that it ceases to work. See the graphic on the left.
Since many enzymes contain sulfhydral (-SH), alcohol, or acid groups as part of their active sites, any chemical which can react with them acts as a noncompetitive inhibitor. Heavy metals such as Ag+, Hg2+, Pb2+ have strong affinities for -SH groups.

13. Competitive v. Noncompetitive