CHAPTER INVESTIGATION
Modeling a Kidney
OVERVIEW AND PURPOSE Your kidneys are your body’s
filters. Every 20 to 30 minutes, every drop of your blood passes
through the kidneys and is filtered. What types of materials are
filtered by the kidneys? In this investigation you will
• model the filtering process of the kidneys
• determine what types of materials are filtered by
your kidneys
Problem
Write
It Up
What types of materials can be removed from the blood by
the kidneys?
Hypothesize
MATERIALS
• fine filter paper
• small funnel
• graduated cylinder
• 100 mL beaker
• solution A
• solution B
• solution C
• salinity test strips
• glucose test strips
• protein test strips
Write
It Up
Write a hypothesis to explain how substances are filtered out of
the blood by the kidneys. Your hypothesis should take the form
of an "If . . . , then . . . , because . . ." statement.
Procedure
Make a data table like the one shown on the sample notebook
page. Fold the filter paper as shown. Place the filter paper in the
funnel, and place the funnel in the graduated cylinder.
Pour 20 mL of solution A into a beaker.
Test the solution for salt concentration
using a test strip for salinity. Record
the results in your notebook. Slowly
pour the solution into the funnel.
Wait for it all to drip through the
filter paper.
618 Unit 5: Human Biology
step 2
Test the filtered liquid for salt concentration
again. Record the results.
Write
Conclude
It Up
1. COMPARE AND CONTRAST In what
Repeat steps 1, 2, and 3 for solution B using
glucose test strips. Record the results in your
notebook.
ways does your model function like a kidney?
How is your model not like a kidney?
step 5
2. INTERPRET Which materials were able to
Repeat steps 1, 2,
and 3 for solution C
using protein test
strips. Record the
results in your
notebook.
pass through the filter and which could not?
3. INFER What materials end up in the urine?
How might materials be filtered out of the
blood but not appear in the urine?
4. APPLY How could a filtering device be
useful in your body?
INVESTIGATE Further
Observe and Analyze
Write
It Up
CHALLENGE Your blood contains many
1. RECORD Be sure your data table is
complete.
2. OBSERVE What substances were present
in solutions A, B, and C?
3. IDENTIFY VARIABLES Identify the variables and constants in the experiment. List
them in your notebook.
chemicals. Some of these chemicals are waste
products, but some are in the blood to be transported to different parts of the body. What other
substances are filtered out of the blood by the
kidneys? Which of the filtered substances are
normally present in the urine? Use a variety of
reference materials to research the chemicals
found in urine. Revise your experiment to test
the ability of your model kidney to filter other
substances.
ney
Modeling a Kid
results
Table 1. Test-strip
Before filtering
After filtering
Solution A
Solution B
Solution C
Chapter 17: Absorption, Digestion, and Exchange 619