ECA: Proteins and Enzymes: Directions: Work in your lab groups to answer the following questions, make sure each member of the group understands all the concepts. Any figures that are mentioned are found in the 8th Edition.

  1. What is the basic structure of an amino acid? Diagram a generic amino acid.
  2. What is an R group?
  3. Explain how amino acids can lead to primary, secondary, tertiary, and quaternary structure in a protein. Explain how R groups can create unique internal structures that are hydrophobic, hydrophilic, polar, or non-polar.
  4. Relate the structures of proteins to membrane proteins. How can the arrangement of R groups facilitate transport of various large macromolecules such as organic molecules (carbohydrates (example sucrose), lipids, protein, or nucleic acids)?
  5. Why is the ΔG (Gibbs free energy) considered when looking at spontaneous and non-spontaneous reactions?
  6. Explain why ΔG can have a negative value? When is ΔG zero?
  7. Relate ΔG to activation energy (E≠A) to exergonic (exothermic) and endergonic (endothermic) reactions.
  8. Relate the tertiary and/or quaternary structure of a protein enzyme to the specificity of an active site and the corresponding substrate. Donít forget to consider the charge or polarity of the substrate.
  9. How do competitive inhibitors work in relationship to the active site? What do non-competitive inhibitors, co-factors, and co-enzymes share in common?
  10. Scientists try to design enzymes to work better in commercial applications (Tide detergent, biofuels), what do scientists need to consider in designing these enzymes?


4.B.1. Interactions between molecules affect their structure and function.

a. Change in the structure of a molecular system results in a change of the function of the system.

b. The shape of enzymes, active sites, and interaction with specific molecules are essential for basic functioning of the enzyme.

Evidence of student learning is a demonstrated understanding of the following concepts:

1. For a simple chemical reaction to occur, the substrate must be complementary to the surface properties (shape and charge) of the active site. In other words, the substrate must fit into the enzymeís active site.

2. Cofactors and coenzymes can either enhance or inhibit enzyme function; this interaction relates to a structural change which alters the activity rate of the enzyme. The enzyme may only become active when all the appropriate cofactors or coenzymes are present and bound to the appropriate places (often the active site) of the enzyme.

3. No specific cofactors or coenzymes are within the scope of the course and exam.

c. Other molecules and the environment in which the enzyme acts can enhance or inhibit enzyme activity. In some systems a competitive inhibitor can bind reversibly to the active site, preventing substrate binding and changing the activity of the enzyme.

d. The change in function of an enzyme can be interpreted from a graphical representation of concentrations as a function of time. These representations demonstrate the relationship between an enzymeís activity and a competitive inhibitor.