Biology 105, Spring 2000
Key to Quiz 2, 15 February 2000

1. (a). There are three kinds of granular leukocytes; these are two of them. Monocytes and lymphocytes are instances of agranular leukocytes.

2. (e). All of these symptoms can give rise to anemia.

3. (e). Blood always enters the heart at the atria. The oxygenated blood enters from the lung to the left atrium.

4. (a). Cytokines are messenger molecules involved in stimulating immune responses against a variety of foreign bodies, including viruses. So suppression of cytokines will make it harder to fight off viral infections. They can play a role in cancer prevention, so without them cancer cells would be harder to recognize, not easier. They're not directly involved in inflammation, allergy, or foreign tissue rejection.

5. (a). The air provides more benefit if it is saturated with moisture and close to body temperature when exchange occurs at the alveoli.

6. (c). The most common reason for excretion of glucose in the urine is overwhelming the glucose-transport mechanisms in the kidney. Kidney failure or a massive overdose on sweets could be reasons for the phenomenon, but they're not the most common reasons.

7. A cytotoxic T cell is a T lymphocyte that attacks and kills antigen-bearing cells. (0.2 points for identifying it as a lymphocyte or an agranular leukocyte; its ability to attack and kill antigen-bearing cells is worth the other 0.3. If it's identified as a leukocyte without reference to the fact that it's agranular or without naming it as a lymphocyte, dock 0.1 point).

8. Emphysema is lung impairment caused by deterioration of the bronchioles, which trap air in the alveoli. (be lenient; give some credit if they mention that it's a form of lung disease; scarring of the alveoli should earn full credit or close to it).

9. A high enough level of drugs should be administered to prevent the immune system from rejecting the tissue; at the same time, if the immune system is depressed too much, the patient is unable to combat disease, producing organisms that enter the body. (0.3 for recognizing that there has to be enough of the drug present to prevent rejection; up to 0.7 for recognizing that if the level is too the body's ability to fight infection will be compromised).

10. Tonsillectomies are rarer now than they used to be because it is better recognized now that the tonsils play a role in defending the body against infection. (0.3 if the student makes clear that a tonsillectomy is the surgical removal of the tonsils; the rest of the point is based on understanding that the tonsils can play a role in fighting off infections).

11. Carbon dioxide is carried from the tissues into the blood by two mechanisms: it is carried in the plasma in solution and it is carried actively in a complex with deoxygenated hemoglobin. The solubilized carbon dioxide is in the form of bicarbonate, produced through the reaction CO2 + H20 --> H2CO3 --> HCO3- + H+ which is catalyzed by carbonic anhydrase; the HCO3- ions are fairly soluble in plasma, so they are taken up into the blood. CO2 complexed with hemoglobin and the bicarbonate ions are carried to the lungs where the bicarbonate is reconverted to CO2 and CO2 is released back out into the air. The predominant mechanism is soluble bicarbonate carried in the plasma. (1 point each for naming the two mechanisms correctly; 1 for describing at least some of the chemistry of the production of bicarbonate from CO2; 1 for saying that more CO2 is carried in bicarbonate form than in hemoglobin).

12. The urinary system provides for homeostasis by helping to regulate (1) the water-salt balance and (2) the pH balance. Water and sodium are actively transported in the nephron back into the bloodstream, and there are controls in place to recycle water and salt and maintain the salt concentration. Bicarbonate ions are reabsorbed in the kidneys and hydrogen ions are secreted; the degree of activation of these processes helps keep the physiological pH balanced. (1 point for mentioning water-salt balance and 1 more for describing how it works. 1 point for mentioning pH balanace and 1 more for describing how it works. Full credit should be given for other forms of homeostatic regulation in the kidneys provided that they're adequately described and correct).