Homework 4

Homework 4 (Due: Oct. 24, 2005)

Enzymes: Isozymes and Regulation

1. Define isozyme and nonfunctional plasma enzyme and discuss the importance of nonfunctional plasma enzymes as a diagnostic tool.

2. Identify the brain, muscle, heart and liver isozyme patterns for creatine phosphokinase and lactate dehydrogenase.

3. Describe how creatine phosphokinase and lactate dehydrogenase can be used in the diagnosis of myocardial infarction.

4. Explain why a combined analysis of plasma glutamyl transpeptidase and alanine aminotransferase is desirable for diagnosing hepatitis in a patient.

5. Define the following types of regulation of enzyme activity: substrate availability, allostery, post-translational modification, interactions with control proteins and zymogens.

6. List 6 ways that proteins can undergo post-translational modification.

7. Identify the 3 amino acids which can undergo phosphorylation.

Case Study 3

Diagram the time course for the appearance in serum of creatine kinase, lactate dehydrogenase and aspartate amino transferase following a myocardial infarction.

Enzyme Mechanisms-Serine Proteases

1. Describe the general roles played by the serine, histidine and aspartate residues in the active site of chymotrypsin.

2. Explain why histidine is found in the active site of many diverse proteases.

3. Diagram the catalytic mechanism of chymotrypsin, identifying the two transition states.

4. Give two examples of other serine proteases and their general physiological role.

5. Define the term proenzyme and give an example of a physiological role for proenzymes.

Overview of Nutrients

1. Define: essential nutrient, protein quality, ideal protein, essential amino acid, biological value, vitamin.

2. List the forms and identifying characteristics of each of the forms of malnutrition.

3. List and define the energy providing nutrients, their major functions in the body and the number of calories (Kcal) furnished by each.

4. Discuss the significance of ethanol as fuel and low vs. high alcohol intake.

5. For each of the 9 water soluble vitamins, list:

(a) major function(s)

(b) RDA (recommended daily allowance).

Vitamins of Carbohydrate and Nitrogen Metabolism

1. Explain how nicotinamide adenine dinucleotide (NAD⁺) and nicotinamide adenine dinucleotide phosphate (NADP⁺) containing enzymes function in energy producing pathways.

2. Explain how flavin adenine dinucleotide (FAD) containing enzymes function in energy producing pathways.

3. List key metabolic pathways in which NAD⁺, NADP⁺ and FAD participate.

4. Compare and contrast dietary and metabolic sources of niacin and riboflavin.

5. Identify the key metabolic pathways in which vitamin B₆ dependent enzymes participate.

6. Distinguish between the dietary and co-enzyme forms of niacin, riboflavin and pyridoxal (pyridoxine).

Antioxidants (Cobalamin and Folic Acid)

1. Identify the major active oxygen (AO) species and compare their relative reactivities.

2. Explain how the following AO species are generated intracellularly:

Singlet Oxygen

Superoxide Anion Radical

Lipid Peroxyl Radical

Hydroxyl Radical

3. List the harmful actions of AO species in cells.

4. Explain how vitamins C, E and the carotenoids act as cellular antioxidants.

5. Discuss the deficiencies, toxicities and RDA for vitamins C, E and the carotenoids.

6. Explain how folate is absorbed and transported.

7. Diagram the function, source, and deficiencies of folic acid and vitamin B₁₂ (cobalamin).

Nucleotides: Composition and Structure

1. List the types and pricipal functions of the nucleic acids.

2. Draw the pyrimidine and purine bases.

3. List the principal chemical building blocks the comprise ribonucleosides, ribonucleotides and draw ATP.

4. Describe the secondary structures of DNA and RNA.

5. List the ways that DNA and RNA can be cleaved or degraded.

6. Define the following terms: double-helix, antiparallel, complementarity, groove, T_m, hyperchromic shift, hybridization.