University of Florida PHA Biology Questions

• List the forms of nitrogen in the nitrogen cycle in order of most oxidized to the most reduced form. [2]
• What are the two key enzymes involved in nitrogen fixation? How does molecular oxygen affect the reductase complex? How is this overcome? [3]
• Compare how glutamate is formed in plants and bacteria versus its formation in animals. [2]
• a) What two amino acids normally supply the nitrogen required for amino acid and nucleotide synthesis? b) What molecule i s a common intermediate in the synthesis of several amino acids AND in nucleotide synthesis? [2]
• a) How is glutamine used in nitrogen metabolism?
  b) Why is the activity of glutamine synthetase tightly regulated? [2]
• What is meant by the term “essential amino acid”? List the six primary precursors used to derive the 20 common amino acids. [2]
• Describe the role of PLP in the biosynthesis of serine, glycine and cysteine. [2]
• List the amino acids synthesized from oxaloacetate and pyruvate. Which amino acids are essential and which are non-essential? [3]
• In what way is the role of ATP in histidine biosynthesis unusual? Propose a possible fate for the inorganic phosphate released at step 8 in histadine biosynthesis. [2]
• Briefly describe the regulatory mechanisms involved in purine and pyrimidine nucleotide synthesis. What is the role of aspartate transcarbamoylase? [3]
• Describe the functions of phosphocreatine and glutathione. [2]
• What do all amino acid decarboxylases have in common? Which of the following is not a conversion reliant upon a decarboxylase? [2]
  • dopa to dopamine
  • glutamate to GABA
  • tryptophan to 5-hydroxytryptophan
• a) Which molecules contribute the nitrogen atoms for purine biosynthesis?
  b) Which reactions in the de novo synthesis of purine nucleotides require energy expenditure? [3]
• Describe the similarities and differences in the de novo synthetic schemes of purines and pyrimidines. [2]
• What happens to purine biosynthesis when excessive AMP accumulates? [2]
• How are nucleotide monophosphates are converted to nucleotide triphosphates? [2]
• How are deoxyribonucleotides are formed from ribonucleotides? [2]
• How do ATP and low and high concentrations of dATP affect the activity of ribonucleotide reductase? [2]
• Using your text and any available web resources, identify a genetic disease that results from an anomaly associated with the biosynthesis of amino acids, nucleotides or related molecules. Provide the name of the disease, its exact biochemical effect on the pathway(s), the resultant physiological and symptomatic aspects, and how it might be treated. [5]
• Locate and read the following article which has implications on the de novo synthesis of guanosine nucleotides . Answer the questions below. [5]

  Murali Dhar TG, Shen Z, Gu HH, Chen P, Norris D, et al. (2003) Bioorganic & Medicinal Chemistry Letters, 13 (20): 3557-3560.

• Specifically what reaction does inosine monophosphate dehydrogenase catalyze?
• With respect to the novel small molecule inhibitors of inosine monophosphate dehydrogenase, what general purpose is sought or served by the carbamate side chain?
• What metal is commonly used in the catalysis of the reactions described in this article?
• Why would the scientists be interested in identifying or developing novel small molecule inhibitors of inosine monophosphate dehydrogenase?
• If you were to take on a follow-up study to this research, what might you investigate?

1.Describe the difference between endocrine and paracrine hormones.

2. What are the possible fates of acetyl CoA produced by the liver?

3. What types of lipids are stored in adipocytes? What triggers mobilization of these lipids?

4. List the compounds used as energy sources by each of the following:

a) Skeletal muscle

b) Cardiac muscle

c) Brain

5. Describe how epinephrine coordinates enzyme activity in the gluconeogenic and glycogen breakdown pathways.

6. At the molecular level, what is the effect of glucagon on cell metabolism?

7. What are the effects of epinephrine on each of the following aspects of metabolism:

a) Glycogen breakdown

b) Glycolysis

c) Glucagon secretion

d) Insulin secretion

8. During conditions of fasting or starvation, what is the limiting factor in using citric acid cycle intermediates for gluconeogenesis?

9. Describe the feedback loop observed in insulin secretion.

10. During starvation what happens to the acetyl co-A made available from stored fats?

11. How are the cellular effects of insulin mediated? How does insulin regulate the activity of glycogen phosphorylase?

12. Adrenalin is stored in and released from membrane bound vesicles. Why are testosterone and estrogen not stored in this manner?

13. Describe the differences between Type 1 and Type 2 diabetes and the kinds of therapy used to control each.

14. Why are peptide hormones are initially synthesized as inactive precursors (prepro- or pro-hormones) and processed to the active hormone?

15. Compare and contrast the mechanisms and locations of the effects of peptide and amine hormones and steroid hormones. (Answer in table form if you wish.)

16. Why are the effects of steroid and thyroid hormones slower in action and lengthier in duration than other types of hormones?

17. What factors are released from the hypothalamus, and what cells do they target?

18. Why are the hormones of the anterior pituitary gland often described as tropic?

19. Cells of the islets of Langerhans are found in the _____________. Glucagon is produced by the ____ cells and insulin by the ____ cells.

20. Which hormones are catecholamines? When acting as hormones, from where are they secreted? Where else might these molecules be found?

21. Briefly describe the major actions of the catecholamines on carbohydrate and lipid metabolism.

22. Describe the general pathways and end products of carbohydrate and lipid metabolism in each of the following mammalian tissues:

a) Liver

b) Adipose

c) Muscle (skeletal and heart)

d) Brain tissues

e) Blood

23. Locate and read the following article. Answer the questions below.

Sandoval DA and Davis SN. (2003) Journal of Diabetes and its Complications, 17 (2): 108-113.

• What exactly is leptin, and how does it relate to the biochemistry of metabolism?
• How do researchers often experimentally induce hypoglycemia?
• Describe how exercise, a stressor, affects the secretion of leptin.
• How might activity of the sympathetic nervous system affect plasma leptin secretion on a molecular level?
• A major function of leptin may be to switch fuel utilization to fat from carbohydrates. T/F