Reference no: EM132266237

Assignment

A. Acute Aspirin Overdose: Relationship to the Blood Buffering System

Focus concept: The carbonic acid-bicarbonate buffering system responds to an overdose of aspirin.

Topics to revise

• Principles of acids and bases, including pKa and the Henderson-Hasselbalch equation.
• The carbonic acid-bicarbonate blood buffering system (see below)

The Blood Buffering System - Case Study

Q1: At pH 2.0 in the stomach, what is the charge on this weak acid ? Q2: At pH 8.5, what is the charge on this weak acid?
It has been shown that salicylates act directly on the nervous system to stimulate respiration. Thus, the patient is hyperventilating due to her salicylate overdose.

Q3: What is the change in O2 level, due to aspirin ingestion, compared to normal?

Q4: After 10 hours of aspirin overdose, how would the blood pH value be described, compared to normal? Q5: What is the effect of the bicarbonate drip on blood pH?

B: Histidine-Proline-rich Glycoprotein (HPRG) as a Plasma pH Sensor

Focus concept: HPRG may serve as a plasma sensor and regulate local pH in extracellular fluid during ischemia or metabolic acidosis.

Topics to revise
• Acid/base properties of amino acids.
• Amino acid structure and protein structure

Q6. How is the binding of HPRG to heparin dependent on pH?

Q7. pK of histidine in HPRG is approximately the pH when half of the HPRG is bound to heparin. From the graph, this pK is:......

Q8. The side chain pK of free histidine residues is 6.0. So at pH 6.0, is the histidine side chain in HPRG charged or neutral?

Q9. What happens to the pH dependence of HPRG binding to heparin, when DEPC is added?

Q10. The side chain pK of free histidine residues is 6.0. So at pH 6.0, is the histidine side chain in HPRG charged or neutral when DEPC is present?

Other plasma proteins have been studied for their ability to bind to glycosaminoglycans. One such protein is kininogen, which is a lysine-rich protein. Like HPRG, kininogen is able to bind to glycosaminoglycans, but this binding is far less sensitive to small fluctuations in physiological pH.

Q11. Why does kininogen bind to glycosaminoglycans easily?

Q12. Why is the binding of kininogen less sensitive to physiological pH changes?

C. The Structure of Insulin

Focus concepts: The three dimensional structure of insulin is examined and sequences of various animal insulins are compared.

Q13. From the list of animals provided, what would be the least number of amino acid changes with respect to human insulin?

Q14. Which animal would serve as the best source of insulin to be used for treating diabetics? (consider the number of residue changes, abundance and availability as well as cost of purification)

Q15. Would the pI values of the most suitable animal insulin be the same as, greater than, or less than human insulin?

Q16 and Q17. Duck and chicken insulin have charged residues substituting for an uncharged polar residue in human insulin. Would the pI values of these animal insulins be the same as, greater than, or less than human insulin?

The immune system produces antibodies to proteins that are non-self and these non-self proteins are recognized because their shape differs from self-proteins. Some people developed allergies to the animal insulin because their immune systems recognized the proteins as foreign.

Q18. Using the data in Table 2, explain why the immune system would be able to distinguish animal insulin from human insulin.

A denaturation/renaturation (similar to the one carried out by Anfinsen with ribonuclease) experiment was carried out using insulin. However, in contrast to Anfinsen's results, only less than 10% of the activity of insulin was recovered when urea and ?-mercaptoethanol were removed by dialysis. (This is the level of activity you would expect if the disulfide bridges paired randomly.) In contrast, if the experiment is repeated with proinsulin, full activity is restored upon renaturation.

Q19. What is the main difference between insulin and proinsulin?

Q20. Why is insulin unable to re-create the disulphide bonds correctly after denaturing?

Attachment:- Assignment.rar