Chapter 4 Review Questions

1. A patient attempted suicide by ingesting 50 aspirin tablets. This led to a fairly severe metabolic acidosis. A decrease of blood pH from 7.5 to 6.5 would be accompanied by which one of the following changes in ion concentration?

A 10-fold increase in hydrogen ion concentration

2. A medical student is attempting to understand the buffering system of the human body and has set up the following experiment in the laboratory to help with their understanding. Consider a biochemical reaction that is taking place in a 0.1 M buffer. The initial pH is 7.4, and the pK _a of the buffer is 7.2. If, in a final reaction volume of 1.0 mL, 10 µmoles of protons are generated, what would be the final pH of the solution?

7.22

3. A patient with an enteropathy (intestinal disease) produced large amounts of ammonia (NH₃) from bacterial overgrowth in the intestine. The ammonia was absorbed through the intestine into the portal vein and entered the circulation. Which of the following is a likely consequence of his ammonia absorption?

Conversion of ammonia to ammonium ion in the blood

4. Which of the following physiologic/pathologic conditions is most likely to result in an alkalosis, provided the body couldn’t fully compensate?

Repeated vomiting of stomach contents, including HCl

5. Laboratory tests on the urine of a patient identified the presence of methylmalonate (⁻OOC–CH(CH₃)–COO⁻). Methylmalonate is best described as which one of the following?

The conjugate base of a weak acid.

6. A patient with influenza has a fever of 101.8°F orally. The excess heat is dissipated throughout the body via a substance that can be best described by which one of the following?

It is a dipolar molecule.

 

7. A patient with hypertension is being treated with hydrochlorothiazide, a diuretic medication that can cause some dehydration and major intracellular electrolyte imbalances. Which one of the following electrolytes might be in imbalance under these conditions?

K+

8. A patient with panic attacks and hyperventilation is in respiratory alkalosis. The excess hydroxide ions were able to overcome which one of the following buffers that has the greatest buffering capacity in and near to normal blood pH?

Dihydrogen phosphate

9. A patient is in early diabetic ketoacidosis. Which one of the following would this patient be expected to exhibit upon examination?

Increased respiratory rate

10. A patient with severe anemia (reduced number of red blood cells in circulation) has a decreased capacity to utilize the bicarbonate buffer system to help maintain blood pH in the normal range. Which one of the following statements best describes the reason for this decreased capacity?

The total amount of carbonic anhydrase in red blood cells is decreased in anemia.

 

11. Water is the solvent of life, yet it only dissociates to a small extent. What is the pK _a of water?

15.7

12. The amino acid glycine has been used as a buffer for a number of biochemical experiments. Glycine contains two ionizable groups, one with a pK _a of 2.34, and the other with a pK _a of 9.60. Glycine would be an effective buffer at which one of the following pH values?

13. Consider a buffer that has a free amino group (X-NH₂) with a pK _a of 8.5. If the buffer is present at a 0.1 M concentration what percentage of the buffer is in the acid form at pH 8.0?

75

14. The major source of metabolic acid in the body is carbon dioxide owing to its ability to be enzymatically converted to which one of the following?

Carbonic acid

15. Histidine is an amino acid with three ionizable groups, one of which has a pK _a of 6.0. This group, when protonated, has a positive charge. If this ionizable group, within a protein, forms an ionic interaction with a negatively charged group, what would you predict would happen to the pK _a of the histidine ionizable group?

Increase