Jennifer Sullivan
Midwood High School
Brooklyn, NY
August 2004
Organisms maintain a dynamic equilibrium that sustains life.
Pre-Lab: Students should have discussed the urinary system, including the function of the kidneys and the composition of urine. They should also be familiar with sugar and protein testing from a previous nutrient lab.
Motivation: Initiate a discussion on why doctors take urine samples. Tell your students that they will be acting like doctors trying to determine what is wrong with their patients.
Preparation:
Control- water and yellow food coloring
Sample A- water and apple juice
Sample B- water, red and yellow food coloring and albumin
Sample A should be from a diabetic person. Add as much juice for a positive sugar test, but try to keep the color dilute.
Sample B should be from a person with damaged kidneys.
Be sure to perform all tests on all samples in both your large flask and the small cups that you will distribute to your students.
Materials per group: 2 test tubes
1 test tube rack
1 test tube holder
1 bottle of Benedict’s solution
1 bottle of Biuret reagent
1 set of goggles
3 cups marked and filled with samples
Transparency: Normal fresh urine samples are transparent. Old samples of urine may be cloudy due to the presence of bacteria growing after the samples were collected. Fresh urine samples that are cloudy may be due to urinary tract infections (bacteria growing inside the urethra) or may indicate the presence of blood cells, pus or fat.
Color: The color of urine depends in part on its concentration. Pale, dilute urine may be the result of drinking large volumes of liquids, but it may indicate diabetes. Dark, concentrated urine may be the result of dehydration or of fever. A smoky-red color may indicate the presence of red blood cells, which may be due to damaged kidneys.
Odor: The normal odor of urine may be altered by several factors. A foul odor in fresh urine can indicate the presence of bacteria. A fruity odor indicates the presence of ketones. Ketones are a product of the breakdown of fat, which can occur due to diabetes or to starvation.
Sugar Content: Sugar may be present in your urine after eating a meal rich in carbohydrates or during periods of stress. However, a consistent finding of sugar in urine may indicate diabetes.
Protein Content: Protein in urine indicates an abnormal condition known as proteinuria. This condition may result from disease or damage to the kidneys.
Procedure: Evaluate the urine samples and place your data in the following table.
|
Characteristics |
Control |
Sample A |
Sample B |
|
Transparency |
|
|
|
|
Color |
|
|
|
|
Odor |
|
|
|
|
Sugar |
|
|
|
|
Protein |
|
|
|
Analysis and Interpretation:
1. Why should urine samples be fresh when they are tested?
____________________________________________________________________________________________________________________________________________________________________________________________________________
2. Describe two changes that occur in urine after bacteria have acted upon it?
____________________________________________________________________________________________________________________________________________________________________________________________________________
3. What are three observations or tests that could indicate that a person has diabetes?
____________________________________________________________________________________________________________________________________________________________________________________________________________
4. Why does your doctor tell you not to eat for several hours before giving a urine sample?
____________________________________________________________________________________________________________________________________________________________________________________________________________
5. What can you conclude about the health of the person who submitted Sample A? Explain.
____________________________________________________________________________________________________________________________________________________________________________________________________________
6. What can you conclude about the health of the person who submitted Sample B? Explain.
____________________________________________________________________________________________________________________________________________________________________________________________________________