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Skip Navigation LinksKCC Home > Academic Departments > Biological Sciences > 11New > Bio 11 Webpages > Unit 4, Lesson 9

Lesson 9 - Proteins as Enzymes

Student Performance Objectives

1. Define catalyst, enzyme, substrate, product and metabolic pathway.
2. Distinguish between extracellular and intracellular enzymes.
3. List and describe 5 conditions that affect the work of enzymes.
4. Define isozyme and explain their diagnostic usefulness.
5. Explain the concept of an enzyme's active site.
6. Explain why it is important for an enzyme to lower the activation energy for a specific
    chemical reaction.


Lesson Outline
A. Enzymes as biological catalysts. Animations of enzyme actions:
    http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_enzymes_work.html
B. Enzymes as molecular machines carrying out a very specific activity.
C. Enzymes working in sequences, as machines in a factory, converting a starting material,
    called the substrate, into a finished product.
D. Functional enzyme sequences called metabolic pathways.
E. Enzyme types.
    1. Extracellular (e.g., digestive like amylase and pepsin).
    2. Intracellular (e.g., glycolytic and Kreb's cycle enzymes).
F. Condition affecting the work of enzymes.
    1. Temperature.
    2. Substrate (reactant) concentrations.
    3. pH.
    4. Salt concentration.
    5. Presence of correct concentrations of coenzymes (usually "B" vitamins) and cofactors
        (usually minerals, also called metals, like magnesium, Mg+2).
    6. Presence of inhibitory, inorganic substances, e.g., heavy, toxic metals like mercury, Hg, or lead, Pb.
    7. Presence of inhibitory organic substances, e.g., various carbon-based molecules used in insecticides
        and herbicides.
G. Enzyme variations by tissue: isozymes and diagnostics for heart, liver and kidney disease.
H. Theory of enzyme function: providing surface for substrate interactions (the enzyme's active
     site) and lowering of the activation energy necessary for the substrates to chemically interact
     with each other.













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