Where have you heard about enzymes, other than in a previous biochemistry class? Perhaps in detergent ads? Or in clinical laboratory tests on a family member? Where else?

Enzymes speed up biochemical reactions by using the structure of the protein to catalyze the biochemistry. Enzymes carry the necessary properties to enable regulation of metabolic pathways. Enzymes are often targets of drugs for inhibition of those metabolic pathways.

1. Are all enzymes proteins?

2. To what extent can chemical reactions be accelerated by enzymes?

3. Do all enzymes accelerate chemical reactions to the same extent?

4. Do enzymes consist of any components other than protein?

5. Are enzymes used up in the chemical reactions they catalyze?

6. In the M-M formalism, what kind of reaction kinetics are observed at very low substrate concentration?

7. What are zero order reaction kinetics? Give an example.

8. What is a competitive inhibitor?

9. What factors does an enzyme utilize to catalyze chemical reactions?

10. What is the difference between competitive and non-competitive inhibition?

11. What is an enzyme assay? How is this used in the clinical lab?

Write these questions down, now, and get them answered: in your study group; in class; from individuals; by email; etc.

Answer the questions in writing that are listed at the beginning of this section.

That will help you remember it.

After understanding by what principles enzymes carry out their catalysis, it is important to understand how this catalysis is regulated. Your job is to obtain for yourself an overview of the regulation of enzymes. By what mechanisms are enzymes regulated? This will lie at the heart of metabolism that you will encounter in the second section of the course. This is part of the process by which you are getting an overall understanding of the functioning of the organism known as your patient (or yourself!).

Just as it is important to have enzymes to speed up essential biochemical reactions, it is also essential to regulate the activity of these enzymes, and thus to control the speed of the metabolic pathways of which these enzymes are a part. This is the means by which we keep all our metabolism under control, each of the metabolic pathways in balance with all the others. If this control is lost, there is disaster looming for the individual. For example, the lack of insulin leads to a loss of control of the metabolic pathway called glycolysis, among other things, and you know the disaster caused by diabetes.

1. By what means can enzymes be regulated?

2. What is the difference between competitive and non-competitive inhibition?

3. What is the difference between irreversible inhibition and reversible inhibition?

4. Is any given enzyme regulated by only one means?

5. How is the blood clotting process regulated?

6. What roles do membranes play in blood clotting?

7. What roles do enzyme synthesis and degradation have in controlling the rate of activity in given cells of a particular enzyme?

8. Question 7 points to the third section of this course in which you will explore gene expression; i.e., how the biosynthesis of enzymes is regulated.

Write these questions down, now, and get them answered: in your study group; in class; from individuals; by email; etc.

Answer the questions in writing that are listed at the beginning of this section.

That will help you remember it.

It is now time to put some of your knowledge of protein structure to work. Your first assignment will be to explore the function of the protein, hemoglobin, in the context of what you have learned about protein structure. In the process, you will see an example of how protein conformation determines function. This study will illustrate fundamental principles of the working of proteins in our bodies. You cannot study all the known examples in the time we have available. Rather, by studying one in depth, you can see patterns that are used by other proteins in other settings to carry out biological function.

You know blood is red; you may well know that the red color is from oxygenated hemoglobin inside the red cells. You likely already know that hemoglobin is involved in the transport of oxygen from the lungs to the tissues. What else do you know?

Hemoblogin binds oxygen in the lungs and releases oxygen in the tissues.

1. You have a patient that is turning blue in your chair; what is one of the things that is happening physiologically?

2. Can you visualize the quaternary structure of hemoglobin and give a description in words and pictures?

3. Compare the structure of hemoglobin and myoglobin - how do differences in structure lead to differences in function?

4. How does the binding of one oxygen affect the binding of another oxygen to hemoglobin?

5. How is oxygen binding to hemoglobin regulated?

6. Can you think of any other proteins that operate biologically with analogous principles of cooperativitiy that are exemplified by hemoglobin?

Write these questions down, now, and get them answered: in your study group; in class; from individuals; by email; etc.

Answer the questions in writing that are listed at the beginning of this section.

That will help you remember it.