Time Estimate for Entire Lab: 1.5 hours

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1 Laboratory 12 Homeostasis (LM pages ) Time Estimate for Entire Lab: 1.5 hours Seventh Edition Changes This was lab 11 in the previous edition. Section 12.3 Kidneys was reorganized; Nephron Structure and Circulation is new. The Experimental Procedure: Urinalysis was clarified. New or updated figure: 12.8 Capillary exchange MATERIALS AND PREPARATIONS Lungs (LM pages ) slide, prepared: lung tissue (Carolina , -5684) microscopes, compound light lens paper 12.2 Liver (LM pages ) wax pencils rulers, plastic millimeter test tubes and racks model, liver (Carolina ) simulated serum samples Benedict s reagent solution 50 ml per student group (Carolina , -7113) boiling water bath hot plate boiling chips, pumice thermometer, Celsius beaker beaker clamps test-tube clamp Test tubes. The exercises in this laboratory require students to add solutions to test tubes. As an expedient, the students are asked to mark off the tubes at various centimeter levels with a ruler and then to fill to these marks. You may prefer to have students use a standard method of measuring volume, such as with a graduated cylinder or a pipette. Most experiments use the standard size test tube. A few experiments require the large size test tube. Mini test tubes can be substituted for most laboratory exercises as long as the total volume in a given tube does not exceed 9 cm. This will reduce the volume of reagents used by approximately one-third. Test tube sizes/volumes are as follows: Mini mm (Carolina ) 1 cm = 1.0 ml Standard mm (Carolina ) 1 cm = 1.5 ml Medium large mm (Carolina ) 1 cm = 2.4 ml Large mm (Carolina ) 1 cm = 4.0 ml 1 Note: Materials and Preparations instructions are grouped by exercise. Some materials may be used in more than one exercise.

2 50 Simulated serum samples (glucose solutions). Prepare a stock glucose solution by adding (while stirring) 40 g of dextrose (D-glucose) to 40 to 50 ml of heated distilled water. Increase volume to 100 ml. Determine the amount of each solution that will be needed, and add this amount of water to six flasks or beakers. Mark the containers as indicated, and add stock dextrose, so that they contain the correct relative amounts of dextrose: A 1 low glucose A 2 same as A 1 B 1 high glucose B 2 least glucose C 1 middle glucose C 2 same as C 1 or prepare 20 ml of each glucose solution per student group as follows: A % glucose (dissolve 0.25 g glucose per 100 ml distilled water) B 1 3% glucose (dissolve 3 g glucose per 100 ml distilled water) C 1 0.5% glucose (dissolve 0.5 g glucose per 100 ml distilled water) A % glucose B 2 0% glucose C 2 0.5% glucose 12.3 Kidneys (LM pages ) model, kidney (Carolina A to -6925A) Chemstrip 6 test strips (Carolina ) simulated urine sample dropping bottle, or bottle with dropper Kidney models. Carolina Biological Supply has a large number of kidney models and model sets that vary widely in price. See the Models section of the Carolina catalog to select the most appropriate one for your needs. Simulated urine sample. The patient is to be diagnosed as having diabetes mellitus. It would be appropriate for the sample to have a low ph and to test positive for glucose and ketones. The presence of ketones (acetone) is caused by excessive fat metabolism. Use the stock glucose solution prepared for the serum samples in the Liver section of this laboratory, or prepare fresh. It is easiest to prepare synthetic urine in 1,000 ml quantities. Using a low concentration hydrochloric acid solution (0.1 M suggested), adjust the ph of 1,000 ml distilled water to ph 5, using ph paper or a ph meter. Add enough of the stock glucose solution and acetone to yield positive tests for glucose and ketones. Approximately 5 ml of stock glucose solution and 4 ml of acetone should be adequate. Test with a dipstick, and add more if necessary. Add phenol red solution to yield a slight urine-yellow color if desired. EXERCISE QUESTIONS 12.1 Lungs (LM pages ) Questions About Lung Function (LM page 158) 1. During gas exchange in the lungs, carbon dioxide (CO 2 ) leaves the blood and enters the alveoli, and oxygen (O 2 ) leaves the alveoli and enters the blood. Label Figure 12.2b to show gas exchange in the lungs. The arrows pointing inward should be labeled CO 2, and the arrows pointing outward should be labeled O State one way the lungs contribute to homeostasis. The lungs oxygenate the blood. 3. Is blood more acidic when it is carrying carbon dioxide? yes, slightly Explain. Carbon dioxide combines with water to form carbonic acid, which dissociates to bicarbonate ions and hydrogen ions. The increase in hydrogen ions makes the blood more acidic. 4. Is blood less acidic when the carbon dioxide exits? yes Explain. Hydrogen ions combine with bicarbonate ions to form carbonic acid, which dissociates to water and carbon dioxide. A decrease in hydrogen ions makes blood less acidic. 5. State another way the lungs contribute to homeostasis. The lungs remove carbon dioxide.

3 Liver (LM pages ) Urea Formation (LM page 161) 1. In the chemical formula for urea that follows, circle the portions that would have come from amino groups: Circle both NH 2 groups. 2. State one way the liver contributes to homeostasis. The liver makes urea, a relatively nontoxic nitrogenous end product. Regulation of Blood Glucose Level (LM page 162) after eating (insulin) > glucose glycogen < - before eating (glucagon) 3. State another way in which the liver contributes to homeostasis. The liver maintains the blood glucose level. Experimental Procedure: Blood Glucose Level After Eating (LM page 162) Table 12.1 Blood Glucose Level After Eating Test Tubes (in Order of Color Change) B 1 C 1 A 1 Source of Serum Hepatic portal vein Hepatic vein Mesenteric artery Results (LM page 163) Which blood vessel a mesenteric artery, the hepatic portal vein, or the hepatic vein contains the most glucose after eating? hepatic portal vein Why do you suppose that the hepatic vein does not contain as much glucose as the hepatic portal vein after eating? The liver removes sugar from the blood and converts it to glycogen. Experimental Procedure: Blood Glucose Level Before Eating (LM page 163) Table 12.2 Blood Glucose Level Before Eating Test Tubes (in Order of Color Change) C 2 A 2 B 2 Source of Serum Hepatic vein Mesenteric artery Hepatic portal vein Results (LM page 163) Which blood vessel a mesenteric artery, the hepatic portal vein, or the hepatic vein contains the most glucose before eating? hepatic vein Why do you suppose that the hepatic vein now contains more glucose than the hepatic portal vein? During fasting, glycogen is being broken down in the liver into glucose in order to increase the blood glucose level. Since the hepatic vein removes venous blood from the liver, its glucose level will be higher than that of the hepatic portal vein, which enters the liver.

4 Kidneys (LM pages ) Nephron Structure and Circulation (LM page 165) 1. With the help of Figure 12.5, list the parts of a nephron and tell whether they are located in the renal cortex or the renal medulla. glomerular capsule (renal cortex), proximal convoluted tubule (renal cortex), distal convoluted tubule (renal cortex), collecting duct (renal cortex and renal medulla), loop of the nephron (renal medulla) 2. With the help of Figure 12.5 and Table 12.3, trace the path of blood toward, around, and away from an individual nephron. Blood goes from a renal artery to an afferent arteriole, to a glomerulus, to an efferent arteriole, to a peritubular capillary network, to a venule, to a renal vein. Kidney Function (LM page 166) Figure 12.6 tubular reabsorption tubular secretion glomerular filtration Glomerular Filtration (LM page 167) 1. In the list that follows, draw an arrow from left to right for all those molecules that leave the glomerulus and enter the glomerular capsule: Glomerulus Cells Proteins Glucose Amino acids Salts Urea Water Glomerular Capsule (Filtrate) 2. What substances are too large to leave the glomerulus and enter the glomerular capsule? cells and proteins Tubular Reabsorption (LM page 167) 1. What would happen to blood pressure if water were not reabsorbed? The blood pressure would get lower. 2. What would happen to cells if the body lost all its nutrients by way of the kidneys? The cells would die. 3. In the list that follows, draw an arrow from left to right for all those molecules that are passively reabsorbed into the blood. Use darker arrows for those that are actively reabsorbed. Proximal Convoluted Tubule Water Glucose Amino acids Urea Salts 4. What molecule is reabsorbed the least? urea Peritubular Capillary darker arrow darker arrow darker arrow

5 53 Questions About Urine Formation (LM page 168) Table 12.4 Urine Constituents Substance In Blood of Glomerulus In Filtrate In Urine Protein (albumin) X Glucose X X Urea X X X Water X X X 1. What molecule is reabsorbed from the collecting duct so that urine is hypertonic? water 2. Based on this table, state one way the kidneys contribute to homeostasis. Kidneys remove waste products from the body. 3. Which organ the lung, liver, or kidney makes urea? liver 4. Which organ excretes urea? kidney 5. Which organ excretes urine? kidney 6. If the blood is more acidic than normal, what ph do you suppose the urine will be? acidic 7. If the blood is more basic than normal, what ph do you suppose the urine will be? basic 8. State another way the kidneys contribute to homeostasis. Kidneys help regulate the ph of the blood. Urinalysis (LM page 168) Experimental Procedure: Urinalysis (LM page 168) Figure 12.7 Tests for: Results leukocytes negative ph low ph protein negative glucose positive ketones positive blood negative Conclusions (LM page 169) According to your results, what condition might the patient have? diabetes mellitus Explain. Diabetes mellitus is primarily diagnosed by glucose in the urine. Glucose is in the urine because insulin is not being produced by the pancreas and the liver is not storing glucose as glycogen. Ketones appear in the urine because the body is metabolizing fat instead of glucose. The urine has a low ph because ketones are strong organic acids. Given that the patient s blood contains excess glucose, why is the patient suffering from excessive thirst and urination? Extra water is needed to wash the excess glucose from the blood. Since neither the liver nor the body cells are taking up glucose, why is the patient tired? Glucose is metabolized in cells to produce ATP molecules. The patient has no energy because of the lack of glucose in the cells. Since cells begin to metabolize fat when glucose is not available, why is this patient losing weight? Metabolism of fat results in weight loss. The metabolism of fat can explain the low ph of the urine. Why? Fat metabolism results in ketone bodies.

6 Capillary Exchange in the Tissues (LM page 170) 1. Figure 12.8 carbon dioxide glucose < > wastes amino acids 2. What type of pressure causes water to exit from the arterial side of the capillary? blood pressure 3. What type of pressure causes water to enter the venous side of the capillary? osmotic pressure Questions About Homeostasis (LM page 170) 1. What organ studied in this lab exchanges gases with the external environment? lungs What gases are exchanged? carbon dioxide for oxygen What happens to the oxygen? Oxygen leaves the alveoli of the lungs and enters the blood. 2. In Figure 12.1, what structure digests food and puts glucose and amino acids into the bloodstream? digestive tract 3. What organ studied in this lab regulates the glucose level of the blood? liver 4. What organ studied in this lab removes urea from the blood? kidneys 5. Name several ways the kidneys contribute to homeostasis. The kidneys contribute to homeostasis by excreting waste products and by regulating ph. LABORATORY REVIEW 12 (LM page 171) 1. What process accounts for gas exchange in the lungs? diffusion 2. What molecule is excreted by the lungs? CO 2 3. What are the air spaces in the lung called? alveoli 4. What blood vessel lies between the intestines and the liver? hepatic portal vein 5. In what form is glucose stored in the liver? glycogen 6. The liver metabolizes the amino group from amino acids to what molecule? urea 7. The hepatic vein enters what blood vessel? inferior vena cava 8. When molecules leave the glomerulus, they enter what portion of the nephron? glomerular capsule 9. Name a substance that is in the filtrate but not in the urine. glucose 10. Glucose in the urine indicates that a person may have what condition? diabetes mellitus 11. Name the process by which molecules move from the proximal convoluted tubule into the blood. tubular reabsorption 12. Where does urine collect before exiting the kidney. renal pelvis 13. Does venous blood in the tissues contain more or less carbon dioxide than arterial blood? more 14. What type of pressure causes water to exit from the arterial side of the capillary? blood pressure Thought Questions 15. Which systemic blood vessel would you expect to have a high glucose content immediately after eating? the hepatic portal vein Explain. The process of digestion releases glucose, which enters the blood at the intestinal capillaries, which eventually drain into the hepatic portal vein. 16. In what ways do the kidneys aid homeostasis. The kidneys rid the body of urea and maintain the blood volume and ph within normal limits.