I. Protein function in a cell can be controlled by regulating either the shape of the protein or the amounts of protein synthesized and degraded.
II. The binding of a modulator molecule to the regulatory site on an allosteric protein alters the shape of the functional binding site, thereby altering
Vander et al.: Human Physiology: The Mechanism of Body Function, Eighth Edition
PART ONE Basic Cell Functions its binding characteristics and the activity of the protein. The activity of allosteric proteins is regulated by varying the concentrations of their modulator molecules.
III. Protein kinase enzymes catalyze the addition of a phosphate group to the side chains of certain amino acids in a protein, changing the shape of the protein's functional binding site and thus altering the protein's activity by covalent modulation. A second enzyme is required to remove the phosphate group, returning the protein to its original state.
SECTION A REVIEW QUESTIONS
ligand binding site chemical specificity affinity saturation competition allosteric modulation allosteric protein functional site regulatory site modulator molecule cooperativity covalent modulation phosphorylation protein kinase phosphoprotein phosphatase
1. List the four characteristics of a protein binding site.
2. List the types of forces that hold a ligand on a protein surface.
3. What characteristics of a binding site determine its chemical specificity?
4. Under what conditions can a single binding site have a chemical specificity for more than one type of ligand?
5. What characteristics of a binding site determine its affinity for a ligand?
6. What two factors determine the percent saturation of a binding site?
7. Describe the mechanism responsible for competition in terms of the properties of binding sites.
8. Describe two ways of controlling protein activity in a cell.
9. How is the activity of an allosteric protein modulated?
10. How does regulation of protein activity by covalent modulation differ from that by allosteric modulation?
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.