BIO 2924 – Unit III
Chapter 8 and 9.3
Enzymes: - Chapter 8
1. Simple Enzymes
2. Conjugated Enzymes
D. Nomenclature of Enzymes
E. Classification of Enzymes
F. Enzyme--Substrate Reactions
G. Levels of Structure of Enzymes
H. Conditions Affecting Enzyme Activity
I. Location and Regularity of Enzyme Action
3. Constitutive Enzymes
4. Inducible Enzymes
J. Regulation of Enzymatic Activity
1. Competitive vs. noncompetitive inhibition
2. Reversible vs. irreversible
3. Energy Link Control
4. Feedback Control
5. Precursor Activation
6. General Processes
K. Regulation of Enzyme Synthesis
1. Constitutive Enzymes
2. Inducible Enzymes
3. Induction – Chapter 9.3
4. Repression – Chapter 9.3
Metabolism - Chapter 8
B. Coupling of Cellular Reaction
1. Free Energy Change
3. Exergonic Reactions
4. Endergonic Reactions
C. Oxidation and Energy Production
D. Biochemical Pathways for Glucose Catabolism
1. Aerobic Respiration
2. Anaerobic Respiration
E. Catabolism of Other Macromolecules
1. Catabolism of Lipids
2. Catabolism of Proteins
An enzyme is an organic catalytic agent produced by a living cell. A catalyst is a substance that has the capacity to speed up chemical reactions without itself being altered after the reaction is complete.
Characteristics of Enzymes
1. Most enzymes are proteins or proteins combined with other chemical groups, and other enzymes (ribozymes) are composed of RNA.
Since enzymes are proteins or RNA molecules,
a. their specific three-dimensional structure is essential to functionality. b. they are often denatured by heat and changes in pH.
c. they cannot cross the plasma membrane via simple diffusion. 2. Enzymes act as organic catalysts to speed up the rate of a reaction. They perform this function by lowering the activation energy required for a chemical reaction to occur. The energy of activation (activation
energy) is the energy required to start a
chemical reaction. It forms a barrier to
a particular reaction, which must be
overcome for a reaction to proceed.
In the laboratory, overcoming the activation energy barrier can be achieved by a. increasing thermal energy (heating) to increase molecular velocity b. increasing the concentration of reactants to increase the rate of molecular collisions
c. adding a catalyst (which lowers the activation energy).
Enzymes contain an active site, a spot where chemical reactants (substrates) are rapidly converted to products
Enzymes are not used up or permanently changed by the reaction taking place between the enzyme and its substrate. Thus they are reusable and usually effective in very low concentrations.
Enzymes are affected by particular environmental conditions, particularly temperature and pH (e.g., An enzyme that would normally function at 37C would most likely be ineffective (and chemically changed) at 50C or higher. An enzyme that would normally function at pH 7 would most likely be ineffective (and chemically changed) at pH 2.) Enzymes can be regulated by feedback and genetic mechanisms.
1. Simple Enzyme – consists only of protein parts
2. Conjugated Enzyme – consists of both protein parts and non-protein molecules *A conjugated enzyme is sometimes referred to as a holoenzyme, which is composed of both a
a. protein portion – called the apoenzyme
b. non-protein portion (cofactor), which is either
1. an inorganic element (metal ion) that these enzymes need to become functional. These metal ions are often trace nutrients that must be supplied to the organism for proper enzyme function.
(*See Table 8.2, pg. 220 for examples)
2. a coenzyme (an organic...
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