Name: ____________________________ Per: _____ Lab Group: ____ Performance:
PRE-LABORATORY QUESTIONS
Write answers on this paper, show all your math!
1. Shown below are three beakers each with a dialysis bag (square box) inside them. They
represent the experiment A1/A2.
I. Label what is inside and outside of each bag initially as described in A1/A2 a, b, and c.
II. Using a colored marker, predict the net movement of water.
A a)
A b)
A c)
2. Now pretend you are Mr. Archer. For this lab I have to make 500 mL of a 30% (m/v) sucrose
solution for one class. How much sucrose in grams do I need to weigh out?
3. Now I have to make 500 mL of a 1.75 M sucrose (MM: 342g/mole) solution. How much sucrose
do I need to weigh out?
4. What is more concentrated? 30% (m/v) or 1.7 M? Since you cannot compare apples with pears
you need to bring both concentrations in to the same unit. Convert 1.7 M into % m/v, now you
are able to compare!
5. Study the patient’s lab report from page 1. Which variables are out of range and by how much.
6. Kidneys have the responsibility to excrete nitrogen that accumulates in the blood, that is a result
of protein breakdown from normal cell turnover - proteins are made and broken down on an
ongoing level. BUN is the Blood-Urine-Nitrogen level and an indicator of kidney health. If the
kidneys are stressed, they cannot excrete enough Nitrogen and it accumulates in the blood.
•
•
Creatinine is an amino acid that indicates muscle breakdown.
Based on the data sheet on page 1, can you make a diagnosis about the patient’s health?
Name: ____________________________ Per: _____ Lab Group: ____ Performance:
BIOCHEMISTRY LAB # 4
SOLUTIONS, CONCENTRATIONS, OSMOSIS, AND DIALYSIS
BACKGROUND
Solutions and Concentrations
Health care professionals work with a variety of solutions, the most common type probably being
intravenous (IV) solutions. A solution is a _____________ of _____________or more substances. In a
solution the substance that is present in the greater amount is called the _____________, while the
substance (or substances) that is present in the smaller amount is called the _____________. Although
most common solutions are liquids, and the most common solvent is water, solutions can be made from
solvents and solutes that are liquids, solids or gases. Body fluids are examples of liquid solutions while
the air we breathe is an example of a solution containing gaseous components.
In solutions, the amount of dissolved solutes can lead to changes in the properties of the
solution. In the case of body fluids the amount of dissolved solutes are maintained within specific limits.
Deviations from these normal limits can indicate the presence of disease. Health care professionals
routinely look at the amounts of solutes to make diagnoses and to determine if therapeutic interventions
are having their desired effects. The amount of a solute dissolved in a certain amount of solution is
called the __________________________ of the solute in the solution.
Take a look at the lab report shown below.
This lab report gives details about the different solutes found in the blood of a patient. Notice
that each solute has a numerical value associated with it. This numerical value is a measure of the
concentration of the solute and health care professionals can use this information to determine the
health of the patient. Notice also that in this particular lab report concentrations are given using two
different units ___________ and ____________. Although concentration values can be expressed in
different ways, they all specify a certain amount of solute in a given amount of solution. Given below are
some of the most common ways of expressing solute concentrations (pay particular attention to the
difference between solvent and solution):
Name: ____________________________ Per: _____ Lab Group: ____ Performance:
Name the 4 common type of concentration measurements
1. ____________________________________
3. ____________________________________
2. ____________________________________
4. ____________________________________
In medicine the concentration of ionic solutes found in body fluids are typically measured in Equivalent
per liter (Eq/L) or milliequivalent per liter (mEq/L). An Equivalent: def:
___________________________________________________________________________.
Ex: 1 mole of Na+ ions has __________ Eq, 1 mole of chloride (Cl-) ions has __________ Eq.
Osmosis
When two solutions with different solute concentrations are separated by a semipermeable
membrane there will be a _______________ movement of water from the solution with the
_______________ solute concentration to the solution with the _______________ solute concentration
to, or attempt to, equalize the concentrations on either side of the membrane. This process, of water
movement through a semipermeable membrane, is called _______________. A semipermeable
membrane is a membrane that allows the movement of _______________ but not the movement of
dissolved _______________. The solution with the higher solute concentration is said to be
_______________ with respect to the solution with the lower solute concentration, while the solution
with the lower solute concentration is said to be _______________ with respect to the solution with the
higher solute concentration. If two solutions with the same solute concentrations are separated by a
semipermeable membrane there will be no net movement of water and the two solutions are said to be
_______________ to each other.
Tonicity is the ability of a solution to cause net water movement. _______________ solutions do
not cause a net movement of water in or out of the cell. _______________ solutions cause a net
movement of water out of the cell, while _______________ solutions cause a net movement of water
into the cell. A red blood cell placed in a hypertonic solution would _______________ water and shrink.
This process is called _______________________________. On the other hand a red blood cell
placed in a hypotonic solution would take in water, _______________. and eventually burst. This
process is called ________________________. Many of the intravenous fluids in medicine are isotonic
solutions and do not cause a net movement of water in or out of cells. Note that the tonicity of a solution
always refers to a comparison, usually with respect to the intracellular fluid.
Dialysis
Dialysis is the movement of solute and solvent _________________a selectively permeable
membrane. These selectively permeable membranes, also known as dialysis membranes, allow water
molecules and certain sized solute molecules to pass through. When two solutions are separated by a
dialysis membrane water and certain solutes (those that have the right size) will move across the
membrane to equalize, or attempt to equalize, the concentration on either side with equalize.
In the body, dialysis takes place at the membranes of the ________________, which removes
waste products, such as urea, excess salt and water from the blood. Artificial kidneys use dialysis to
remove waste products from patients with kidney failure. This process is called hemodialysis
Name: ____________________________ Per: _____ Lab Group: ____ Performance:
PROCEDURE
The goal of this laboratory is to introduce you to the concept of solute concentration and osmosis and
dialysis. You will be given solutions with different solute concentrations which you will use to observe
the process of osmosis. Finally you will use dialysis to separate out glucose and chloride ions from a
mixture of chloride ions, glucose, and starch.
A. OSMOSIS
Materials: 3 x dialysis tubing, 3 x 250 mL beakers, beral pipette, distilled water, 30% (m/v) sucrose
solution, 1.75 M sucrose solution.
A.1. You will be given three pieces of dialysis tubing of equal length (8-10 cm). Soak them in a beaker
with water for about 10 min to hydrate them. Tie a knot at the end of each bag and fill half with 30%
(m/v) sucrose solution using a beral pipette. Gently squeeze out any air above the liquid and close bag
with another knot. Rinse bags with tap water, pat dry using a paper towel to remove any liquid from the
outside of the bag and weigh the bag. Record the weight of each bag. DO NOT MIX UP BAGS!
A.2. Label three labeled beakers and fill with (a) 50 mL of distilled/deionized water, (b) 50 mL of 30 %
(m/v) sucrose, and (c) 50 mL of 1.75 M sucrose. Be sure to keep track of the bags placed in each
solution by labeling the beakers. Allow the bags to remain undisturbed in each solution for 30 min.
Gently swirl the beaker every 5 minutes. At the end of the 30 minutes quickly remove each bag, rinse
the bag well with distilled water, gently pat the bag completely dry to remove any liquid from the
outside the bag and reweigh the bag. Record your results for each bag.
B. IDENTIFICATION TESTS FOR CHLORIDE, GLUCOSE AND STARCH
Materials: 10% NaCl solution, AgNO3 solution, 10% glucose solution, Benedict’s reagent, microcentrifuge tubes.
B.1. Chloride test
Place 5-6 drops of 10% NaCl in one well and 5-6 drops of deionized (DI) water in another well of a
plastic well plate. The well with water will be the control or comparison sample. Test for Cl- by adding 1
drop of AgNO3 to each. Record your observations. Compare the results for the NaCl solution with the
results of the water sample.
B.2. Glucose test
Place 0.25 mL of 10% glucose solution in a micro-centrifuge tube. Place 0.25 mL of DI water into
another micro-centrifuge tube. Add 9 drops of Benedict’s reagent to the glucose and water. Heat both
tubes in a boiling water bath for 5 minutes. Record your observations. Remove tube from the water,
label them and keep on table for comparison reasons. Note: Each time you carry out the glucose test,
the tube containing Benedict’s reagent must be heated in a boiling water bath.
B.3. Starch test
Place 5-6 drops of 1% starch solution in one well and 5-6 drops of DI water in another well of a plastic
well plate. Add 1 drop of iodine reagent to each. Record your observations. Compare the results for
the starch sample with the results for the water sample.
Name: ____________________________ Per: _____ Lab Group: ____ Performance:
C. DIALYSIS
Materials: 10% NaCl solution, AgNO3 solution, 10% glucose solution, Benedict’s reagent, dialysis
tubing, dialysis tubing clips, 100 mL beakers, distilled water.
In a small beaker combine approx. 1 mL of 10% NaCl, 1 mL of 10% glucose, and 1 mL of 1% starch
solution. Clip one end of a 4-5 cm long piece of dialysis tubing. Fill a dialysis bag with the mixture, rinse
bag with water to remove any of the mixture that may be on the outside of the bag, pat dry and place in
a beaker with about 30 mL of distilled water, making sure bag is submerged.
C.1. Immediately remove 1-2 mL sample of the water in the beaker (surrounding the dialysis bag).
Divide the sample into 2 test wells (about 4-5 drops each) and a micro-centrifuge tube. Repeat each of
the three identification tests that you did in part on these three samples (one test per sample).
A substance is present in the sample if a test for that substance gives the same results as in the
identification tests in part B. Record the result as positive (+). If the substance is absent (there is no
chemical reaction), record the test as negative (-).
C.2. Repeat the procedures in part B after 15 minutes of placing the bag in the beaker.
C.3. Repeat the procedures in part B after 30 minutes of placing the bag in the beaker.
C.4. After the 30 minute test, open the bag and remove the contents and perform the three identification
tests for chloride, glucose and starch.
Name: ____________________________ Per: _____ Lab Group: ____ Performance:
REPORT SHEET
A. OSMOSIS
Distilled water
30% sucrose
1.75 M sucrose
A.1. Initial weight of dialysis bag (g)
A.2. Final weight of dialysis bag (g)
Change in weight (g)
B. IDENTIFICATION TESTS FOR CHLORIDE, GLUCOSE AND STARCH
Test performed Reagent Added Observations with test solution Observations with water (control)
B.1. Chloride
B.2. Glucose
B.3. Starch
C. DIALYSIS
Observations for:
Time
C.1.
Chloride test
0 minutes
C.2. 15 minutes
C.3. 30 minutes
C.4. Contents of
bag
Glucose test
Starch test
Name: ____________________________ Per: _____ Lab Group: ____ Performance:
QUESTIONS
1. Imagine that the dialysis bag you used in part A is a ‘cell’ and that the solution inside the bag is
intracellular fluid.
a. Which solution is isotonic to the fluid inside the bag?
b. Which solution is hypertonic to the fluid inside the bag?
c. Which solution is hypotonic to the fluid inside the bag?
2. What would have happened in each of the three beakers in part A if the bags were filled with
distilled water instead of the 30% sucrose solution?
3. In part C which substances were found in the solution outside the dialysis bag?
4. How did these substances in question 3 go into the solution outside the bag?
5. What substances were retained inside the bag in part C? Why were they retained?
6. 0.9 % (m/v) NaCl and 5% (m/v) glucose solutions are said to be isotonic with respect to the
intracellular fluid of red blood cells. A red blood cell placed in these solutions would undergo
neither crenation nor hemolysis (i.e. no change in the red blood cell would occur). Given this
information predict if a red blood cell would undergo crenation, hemolysis, or no change in the
following solutions:
a.
b.
c.
d.
2% (m/v) glucose
2% (m/v) NaCl
0.1% (m/v) NaCl
10% (m/v) glucose
7. Are the solutions given above isotonic, hypotonic or hypertonic with respect to the intracellular
fluid of a red blood cell?