Your Full Name: UMUC Biology 102/103 Lab2:The Chemistry of Life INSTRUCTIONS:

Your Full Name:

UMUC Biology 102/103
Lab2:The Chemistry of Life
INSTRUCTIONS:

Pre-Lab Questions

Nitrogen
fixation is a natural process by which inert or unreactive forms of
nitrogen are transformed into usable nitrogen. Why is this process
important to life?

Given
when you have learned about the hydrogen bonding shared between nucleic
acids in DNA, which pair is more stable under increasing heat: adenine and
thymine, or cytosine and guanine? Explain why.

Which of the following is not an organic
molecule; Methane (CH4), Fructose (C6H12O6),
Ethanol (C6H12O), or Ammonia (NH3)? How
do you know?

Experiment
1: Testing for Proteins

Materials
(2) 250 mL
Beakers
25 Drops Biuret Solution, H2NC(O)NHC(O)NH
(1) Knox Gelatin Packet
5 mL 1% Glucose Solution, C6H12O6
(1) 10 mL Graduated Cylinder
(1) 100 mL Graduated Cylinder
Permanent Marker
5 Pipettes

5 Test Tubes
(Glass)
Test Tube Rack
5 mL Unknown Solution
Egg White
Hot Water
Tap Water

The protein molecules in many
foods provide the amino acid building blocks required by our own cells to
produce new proteins. To determine whether a sample contains protein, a reagent
called Biuret solution is used. Biuret solution contains copper ions, similar
to Benedicts solution (another common reagent). However, the chemical state of
the copper ions in Biuret solution causes them to form a chemical complex with
the peptide bonds between amino acids (when present), changing the color of the
solution. Biuret solution is normally blue, but changes to pink when short peptides
are present and to violet when long polypeptides are present.

.0/msohtmlclip1/01/clip_image001.jpg” alt=”Figure 6: biuret solution only is located on the far left side of the image (blue). note the transition from blue to violet as proteins are added to the solution, causing the solution to transition from blue to violet. “>

Figure 6: Biuret
solution only is located on the far left side of the image (blue). Note the
transition from blue to violet as proteins are added to the solution, causing
the solution to transition from blue to violet.

Procedure

Predicted results based on a previously learned set
of information is sometimes called an a priori prediction. Before
you begin, take a moment to construct a priori predictions stating whether
or not there are proteins present in each of the following solutions:
Albumin (Egg White), Knox Gelatin, Glucose, and Water. Record these
predictions in Table 1.
Then, use your knowledge of Biuret solution
chemistry (refer to the experimental introduction) to predict the color of
each of the four solutions when mixed with Biuret solution. You must
predict the initial color, as well as the final color (the color after ).
Record these predictions in Table 1.
You may now begin your experiment by using the
permanent marker to label five test tubes 1, 2, 3, 4 and 5.
Prepare your testing samples as follows:

Mix one egg white with 25 mL water in a 250 mL
beaker to create an albumin solution. Pipette 5 mL of this solution into
Test Tube 1.
Mix the packet of Knox gelatin with 50 mL hot
water in a second 250 mL beaker. Stir until dissolved. Pipette 5 mL of
this solution into Test Tube 2.

Pipette 5 mL of the 1% glucose solution into Test
Tube 3.
Use the 10 mL graduated cylinder to measure and pour
5 mL of water into Test Tube 4.
Pipette 5 mL of the Unknown Solution into Test
Tube 5.
Add five drops of Biuret solution to each test tube.
Swirl each tube to mix.
Record the initial color of each sample in Table 2.
Record the final color in Table 2.
Note: Protein is present in the sample if a light purple color is
observed.

Data Tables and Post-Lab Assessment
Table 1: A Priori Predictions

Table
1: A Priori Predictions

Sample

Will
There be Protein Present?

Initial
Color

Final
Color

1 – Albumin Solution

2 – Gelatin Solution

3 – Glucose

4 – Water

5 – Unknown

Table 2: Testing for Proteins Results

Table
2: Testing for Proteins Results

Sample

Initial
Color

Initial
Color

Is
Protein Present?

1 – Albumin Solution

2 – Gelatin Solution

3 – Glucose

4 – Water

5 – Unknown

Post-Lab
Questions

1. How did your a priori
predictions from Table 1 compare to your actual results in Table 2? If there
were any inconsistencies, explain why this occurred.

2. Identify the positive and negative
controls used in this experiment. Explain how each of these controls are used,
and why they are necessary to validate the experimental results.

3. Identify two regions which
proteins are vital components in the human body. Why are they important to
these regions?

4. Diet and nutrition are
closely linked to the study of biomolecules. Describe one method by which you
could monitor your food intake to ensure the cells in your body have the
materials necessary to function.

Experiment 2: Testing for Reducing Sugars
Many of the foods we eat contain
carbohydrates. Monosaccharides and short chains such as disaccharides taste
sweet due to certain aspects of their chemical structure. A structural
characteristic of some sugars can be identified using a chemical solution
called Benedicts reagent. When heated, the copper ions in Benedicts solution
react with the free end of any reducing sugars, such as glucose molecules.
Copper ions are reduced by the sugars, producing an orange or red colored
precipitate.

Materials
5 mL Benedicts
Solution
5 mL 1% Glucose Solution, C6H12O6
10 mL Graduated Cylinder
Permanent Marker
3 Pipettes
Ruler
Spatula
5 Test Tubes (Glass)
Thermometer
5 mL Unknown Solution

Fork
Hot Water Bath (stovetop or microwave and a deep, heat-safe bowl)
Knife
Onion
Potato
Stopwatch
Tap Water

Many of the
foods we eat contain carbohydrates. Monosaccharides and short chains such
as disaccharides taste sweet due to certain aspects of their chemical
structure. A structural characteristic of some sugars can be identified
using a chemical solution called Benedicts reagent. When heated, the
copper ions in Benedicts solution react with the free end of any reducing
sugars, such as glucose molecules. Copper ions are reduced by the sugars,
producing an orange or red colored precipitate.

Materials
5 mL Benedicts
Solution
5 mL 1% Glucose Solution, C6H12O6
10 mL Graduated Cylinder
Permanent Marker
3 Pipettes
Ruler
Spatula
5 Test Tubes (Glass)
Thermometer
5 mL Unknown Solution

*Fork
*Hot Water Bath (stovetop or microwave and a deep, heat-safe bowl)
*Knife
*Onion
*Potato
*Stopwatch
*Tap Water
*You Must
Provide

Note: Use great caution when handling a knife and/or
cutting. Ask for assistance if you need help or are uncomfortable with knife
work.
Procedure

Label five test tubes as 1 – 5.
Prepare your testing samples as follows:

Cut a raw potato into a 1.0 cm x 1.0 cm x 1 cm
cube. Cut this cube into smaller pieces, and mash with a fork and
approximately 5 – 10 drops of water. Place half of the mashed raw
potato into Test Tube 1. Use the 10 mL graduated cylinder to measure
and pour 5 mL of water into Test Tube 1.
Cut a raw onion into a 1.0 cm x 1.0 cm x 1.0 cm
cube. Cut this cube into smaller pieces, and finally mash with a clean
or new fork. Place half of the mashed raw onion into Test Tube 2. Use
the 10 mL graduated cylinder to measure and pour 5 mL of water into
Test Tube 2.

Pipette 5 mL of the 1% glucose solution into Test
Tube 3.
Use the 10 mL graduated cylinder to measure and
pour 5 mL of water into Test Tube 4.
Pipette 5 mL of the Unknown solution into Test
Tube 5.
Record the initial color of each solution in Table
3.
Prepare a hot water bath using the following
information:

Heat water to a temperature between 85 and 100 C
(not boiling) using a stovetop or microwave safe container. Be sure to
confirm this temperature using the thermometer just prior to use in
Step 9. The hot water bath must be of appropriate size and shape to fit
five glass test tubes in a vertical orientation.

Pipette 10 drops of Benedicts Solution to each
test tube. Swirl each tube gently to mix.
Place the five test tubes into the hot water bath
and let sit for three minutes. Remove the tubes from water and place
them in test tube rack to cool for five minutes.
Record the final color in Table 3.
Note: A reducing sugar is present in the sample if a red, yellow
or green precipitant forms. Wash your test tubes immediately after
recording results to prevent permanent staining from the reaction
products.

Data Tables and Post-Lab Assessment
Table 3:Testing for Reducing Sugars Results

Table
3: Testing for Reducing Sugars Results

Sample

Initial
Color

Final
Color

Reducing
Sugar Present

1 – Potato

2 – Onion

3 – Glucose Solution

4 – Water

5 – Unknown

Post-Lab Questions
1.
Write
a statement to explain the molecular composition of the unknown solution based
on the results obtained during testing with each reagent.
2.
What
can you conclude about the molecular make-up of potatoes and onions based on
the test you performed? Why might these foods contain these substance(s)?

3.
What
results would you expect if you tested ribose, a monosaccharide, with
Benedicts solution? Biuret solution?

Experiment 3: What Household Substances are Acidic or Basic?
In the following experiment,
you will be using pH test strips to determine the pH of various household
substances. pH stands for potential hydrogen and is broken into a scale of 1
– 14 to indicate the acidity or basicity of a solution. Generally speaking,
more hydrogen ions in a solution correlates to lower pH values, and more acidic
solutions. Conversely, fewer hydrogen ions correlates to higher pH values, and
more basic solutions. 7 is located in the middle of this number scale, and
represents neutral solutions.

.0/msohtmlclip1/01/clip_image002.jpg” alt=”Figure 1: “>

Figure 7: Note that many strong acids and bases do not have a pH that
is indicated on this scale. For example, lead battery acid has a pH that is
below one.

Refer to the color key provided
in the module with your pH test strips to determine which color corresponds to
each pH value. In this way, pH paper allows scientists to determine to what
degree a substance is acidic or basic and can provide an approximate pH value.

Materials
5 mL 4.5% Acetic
Acid (Vinegar), C2H4O2
(3) 100 mL Beakers
(3) 250 mL Beakers
10 mL Graduated Cylinder
(10) pH Test Strips
5 mL Sodium Bicarbonate (Baking Soda)Solution, NaHC)3

4 Liquid,
Household Solutions
Paper Towels
Water Source (Jug or Sink)

Procedure

Find four household substances to test (ex: grape
juice, lemon juice, dishwashing liquid, milk, tomato juice, shampoo, corn
starch solution, etc.). You will use the vinegar (acidic) and sodium
bicarbonate (basic) solution provided in your kit as standards.
Predict the pH of each substance before testing with
a pH strip. Record your predictions in Table 4.
Use the permanent marker to label each of the
beakers with the name of one of the six solutions. It does not matter
which size beaker is used for the different solutions.
Use the graduated cylinder to measure and pour five
mL of vinegar into the beaker labeled Vinegar.
Thoroughly rinse the graduated cylinder with water
to remove any remaining vinegar. Use paper towels to dry the graduated
cylinder and repeat Step 4 with each of the five remaining solutions and
beakers.
Measure the pH of each solution by dipping the pad
of the pH strip into the solution for 5 – 10 seconds and comparing it with
the pH test strip key (located in the lab module). Record your results in
Table 4.

Data Tables and Post-Lab Assessment
Table 4:pH Values of Common Household Substances

Table
4: pH Values of Common Household Substances

Substance

pH Prediction

pH Test Strip Color

Acetic Acid (Vinegar)

Sodium Bicarbonate Solution (Baking
Soda)

Post-Lab Questions

1.
What
is the purpose of determining the pH of the acetic acid and the sodium
bicarbonate solution before testing the other household substances?

2.
Compare
and contrast acids and bases in terms of their H+ ion and OH-
ion concentrations.

3.
Name
two acids and two bases you often use.
Your Full Name: UMUC Biology 102/103Lab2:The Chemistry of LifePre-Lab QuestionsExperiment
1: Testing for Proteins Materials(2) 250 mL
Beakers
25 Drops Biuret Solution, H2NC(O)NHC(O)NH
(1) Knox Gelatin Packet
5 mL 1% Glucose Solution, C6H12O6
(1) 10 mL Graduated Cylinder
(1) 100 mL Graduated Cylinder
Permanent Marker
5 Pipettes 5 Test Tubes
(Glass)
Test Tube Rack
5 mL Unknown Solution
Egg White
Hot Water
Tap WaterThe protein molecules in many
foods provide the amino acid building blocks required by our own cells to
produce new proteins. To determine whether a sample contains protein, a reagent
called Biuret solution is used. Biuret solution contains copper ions, similar
to Benedicts solution (another common reagent). However, the chemical state of
the copper ions in Biuret solution causes them to form a chemical complex with
the peptide bonds between amino acids (when present), changing the color of the
solution. Biuret solution is normally blue, but changes to pink when short peptides
are present and to violet when long polypeptides are present..0/msohtmlclip1/01/clip_image001.jpg” alt=”Figure 6: biuret solution only is located on the far left side of the image (blue). note the transition from blue to violet as proteins are added to the solution, causing the solution to transition from blue to violet. “>Figure 6: Biuret
solution only is located on the far left side of the image (blue). Note the
transition from blue to violet as proteins are added to the solution, causing
the solution to transition from blue to violet. ProcedureData Tables and Post-Lab AssessmentTable 1: A Priori PredictionsTable
1: A Priori PredictionsSampleWill
There be Protein Present?Initial
ColorFinal
Color1 – Albumin Solution 2 – Gelatin Solution 3 – Glucose 4 – Water 5 – Unknown Table 2: Testing for Proteins ResultsTable
2: Testing for Proteins ResultsSampleInitial
ColorInitial
ColorIs
Protein Present?1 – Albumin Solution 2 – Gelatin Solution 3 – Glucose 4 – Water 5 – Unknown Post-Lab
Questions1. How did your a priori
predictions from Table 1 compare to your actual results in Table 2? If there
were any inconsistencies, explain why this occurred. 2. Identify the positive and negative
controls used in this experiment. Explain how each of these controls are used,
and why they are necessary to validate the experimental results.3. Identify two regions which
proteins are vital components in the human body. Why are they important to
these regions?4. Diet and nutrition are
closely linked to the study of biomolecules. Describe one method by which you
could monitor your food intake to ensure the cells in your body have the
materials necessary to function.Experiment 2: Testing for Reducing Sugars Many of the foods we eat contain
carbohydrates. Monosaccharides and short chains such as disaccharides taste
sweet due to certain aspects of their chemical structure. A structural
characteristic of some sugars can be identified using a chemical solution
called Benedicts reagent. When heated, the copper ions in Benedicts solution
react with the free end of any reducing sugars, such as glucose molecules.
Copper ions are reduced by the sugars, producing an orange or red colored
precipitate.Materials5 mL Benedicts
Solution
5 mL 1% Glucose Solution, C6H12O6
10 mL Graduated Cylinder
Permanent Marker
3 Pipettes
Ruler
Spatula
5 Test Tubes (Glass)
Thermometer
5 mL Unknown Solution Fork
Hot Water Bath (stovetop or microwave and a deep, heat-safe bowl)
Knife
Onion
Potato
Stopwatch
Tap WaterMany of the
foods we eat contain carbohydrates. Monosaccharides and short chains such
as disaccharides taste sweet due to certain aspects of their chemical
structure. A structural characteristic of some sugars can be identified
using a chemical solution called Benedicts reagent. When heated, the
copper ions in Benedicts solution react with the free end of any reducing
sugars, such as glucose molecules. Copper ions are reduced by the sugars,
producing an orange or red colored precipitate. Materials5 mL Benedicts
Solution
5 mL 1% Glucose Solution, C6H12O6
10 mL Graduated Cylinder
Permanent Marker
3 Pipettes
Ruler
Spatula
5 Test Tubes (Glass)
Thermometer
5 mL Unknown Solution *Fork
*Hot Water Bath (stovetop or microwave and a deep, heat-safe bowl)
*Knife
*Onion
*Potato
*Stopwatch
*Tap Water*You Must
ProvideNote: Use great caution when handling a knife and/or
cutting. Ask for assistance if you need help or are uncomfortable with knife
work. ProcedureData Tables and Post-Lab AssessmentTable 3:Testing for Reducing Sugars ResultsTable
3: Testing for Reducing Sugars ResultsSampleInitial
ColorFinal
ColorReducing
Sugar Present1 – Potato 2 – Onion 3 – Glucose Solution 4 – Water 5 – Unknown Post-Lab Questions1.
Write
a statement to explain the molecular composition of the unknown solution based
on the results obtained during testing with each reagent.2.
What
can you conclude about the molecular make-up of potatoes and onions based on
the test you performed? Why might these foods contain these substance(s)?3.
What
results would you expect if you tested ribose, a monosaccharide, with
Benedicts solution? Biuret solution?Experiment 3: What Household Substances are Acidic or Basic? In the following experiment,
you will be using pH test strips to determine the pH of various household
substances. pH stands for potential hydrogen and is broken into a scale of 1
– 14 to indicate the acidity or basicity of a solution. Generally speaking,
more hydrogen ions in a solution correlates to lower pH values, and more acidic
solutions. Conversely, fewer hydrogen ions correlates to higher pH values, and
more basic solutions. 7 is located in the middle of this number scale, and
represents neutral solutions. .0/msohtmlclip1/01/clip_image002.jpg” alt=”Figure 1: “>Figure 7: Note that many strong acids and bases do not have a pH that
is indicated on this scale. For example, lead battery acid has a pH that is
below one.Refer to the color key provided
in the module with your pH test strips to determine which color corresponds to
each pH value. In this way, pH paper allows scientists to determine to what
degree a substance is acidic or basic and can provide an approximate pH value. Materials5 mL 4.5% Acetic
Acid (Vinegar), C2H4O2
(3) 100 mL Beakers
(3) 250 mL Beakers
10 mL Graduated Cylinder
(10) pH Test Strips
5 mL Sodium Bicarbonate (Baking Soda)Solution, NaHC)3 4 Liquid,
Household Solutions
Paper Towels
Water Source (Jug or Sink)ProcedureData Tables and Post-Lab AssessmentTable 4:pH Values of Common Household SubstancesTable
4: pH Values of Common Household SubstancesSubstancepH PredictionpH Test Strip ColorAcetic Acid (Vinegar) Sodium Bicarbonate Solution (Baking
Soda) Post-Lab Questions1.
What
is the purpose of determining the pH of the acetic acid and the sodium
bicarbonate solution before testing the other household substances?2.
Compare
and contrast acids and bases in terms of their H+ ion and OH-
ion concentrations.3.
Name
two acids and two bases you often use.