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Biology 30S Name:
Digestion and Nutrition
Kelvin High School
The
BBiioocchheemmiissttrryy Crash Course
The following is an investigation into the basic biochemistry and identification of Carbohydrates, Proteins
and Fats. These groups of organic molecules are important to the normal function of the human body and
will be frequently encountered as we explore the Human Digestive System. Each section of this “Crash
Course” deals with one group of molecules. Read each section carefully and complete each of the
required tasks.
Section One: Carbohydrates
The Chemistry of Carbohydrates: Answer the following questions in the spaces provided. You may need to refer to your notes or
your text book in order to properly answer these questions
1. What is a Carbohydrate?
2. Define the following terms:
(a) Monosaccharide
(b) Disaccharide
(c) Polysaccharide
3. Identify the following molecules:
Biology 30S Name:
Digestion and Nutrition
Kelvin High School
4. How do you draw the following:
Monosaccharide, Disaccharide, Polysaccharide
5. How is a Polysaccharide assembled from Monosaccharides?
The Task has been
completed satisfactorily
Biology 30S Name:
Digestion and Nutrition
Kelvin High School
Identification of Carbohydrates:
Materials: Test tubes Test tube rack Grease pencil
Benedict’s Solution Iodine Solution Droppers
Hot Plate / Water Bath Beakers Test tube clamps
Monosaccharide Solution Disaccharide Solution Polysaccharide Solution
Apple juice Oat solution Table sugar solution
Honey solution Powdered Sugar solution
Procedure #1: Testing Known Carbohydrates
Benedict’s Test:
1. Prepare a hot water bath (your teacher will do this for you)
2. Get three test tubes and number them one to three using a grease pencil
3. Using a clean dropper for each tube, add the following:
Tube #1 – 30 drops of monosaccharide solution
Tube #2 – 30 drops of disaccharide solution
Tube #3 – 30 drops of polysaccharide solution
4. Add 30 drops of Benedict’s Solution to each tube. Use the diagram below as a guide:
.
5. Observe the tubes and record your observations in the table below.
6. Place the three test tubes into a hot water bath for five minutes
7. Use a test tube clamp to remove the tubes from the hot water bath
8. Observe the tubes again and record your observations in the table below.
Table #1: Benedict’s Test With Known Carbohydrates
Tube
Number
Carbohydrate
Type
Benedict’s Colour Before
Heating
Benedict’s Colour After
Heating
#1 Monosaccharide Blue Orange #2 Disaccharide Blue Blue #3 Polysaccharide Blue Blue
Biology 30S Name:
Digestion and Nutrition
Kelvin High School
Iodine Test: 1. Get three cleans and number them one to three using a grease pencil.
2. Using a clean dropper for each tube, add the following:
Tube #1 – 30 drops of Monosaccharide Solution
Tube #2 – 30 drops of Disaccharide Solution
Tube #3 – 30 drops of Polysaccharide Solution
3. Observe the test tubes and record your results in the table below.
4. Add 4 drops of Iodine Solution to each tube. Use the diagram below as a guide:
5. Mix the contents of each tube by gently swirling the test tube
6. Observe the test tubes and record your results in the table below.
Table #2: Iodine Test With Known Carbohydrates
Tube
Number
Carbohydrate
Type
Carbohydrate Colour
Before Adding Iodine
Carbohydrate Colour
After Adding Iodine
#1 Monosaccharide Pale yellow Pale yellow
#2 Disaccharide Pale yellow Pale yellow
#3 Polysaccharide Pale yellow Dark Blue
The Task has been
completed satisfactorily
Biology 30S Name:
Digestion and Nutrition
Kelvin High School
Procedure #2: Testing Unknown Carbohydrates
By comparing the results of this procedure with the Benedict’s and Iodine test results completed
in the previous section, you should be able to identify some unknown carbohydrates as a
monosaccharide, disaccharide, or polysaccharide.
1. Get 5 clean test tubes and number them one to five with a grease pencil
2. Using a clean dropper, add the following to each tube:
Tube #1 – 20 drops of Honey Solution
Tube #2 – 20 drops of Liquid Oats
Tube #3 – 20 drops of Table Sugar Solution
Tube #4 – 20 drops of Apple Juice
Tube #5 – 20 drops of Powdered Sugar Solution
3. Add 30 drops of Benedict’s Solution to each test tube. Use the diagram below as a guide:
4. Place all five test tubes into a hot water bath for five minutes
5. Remove the test tubes from the bath using a test tube clamp
6. Observe the tubes and record your observations in the Benedict’s Test column of Table #3
7. Get 5 more clean test tubes and label them one to five with a grease pencil
8. Using a clean dropper for each tube, add the following to each tube:
Tube #1 – 20 drops of Honey Solution
Tube #2 – 20 drops of Liquid Oats
Tube #3 – 20 drops of Table Sugar Solution
Tube #4 – 20 drops of Apple Juice
Tube #5 – 20 drops of Powdered Sugar Solution
Biology 30S Name:
Digestion and Nutrition
Kelvin High School
9. Add 4 drops of Iodine Solution to each tube and mix by swirling. Use the following diagram
as a guide:
10. Observe the tubes and record your results in the Iodine Test Results column of Table #3
11. Based on the results of both tests, classify each carbohydrate as a monosaccharide,
disaccharide or polysaccharide and record your answers in Table #3
Table #3: Results of Tests With Unknown Carbohydrates
Carbohydrate Benedict’s Test Results Iodine Test Results Type of Carbohydrate
Honey orange Pale yellow
Oats blue Dark blue
Table Sugar blue Pale yellow
Apple Juice orange Pale yellow
Powdered Sugar blue Pale yellow
The Task has been
completed satisfactorily
Biology 30S Name:
Digestion and Nutrition
Kelvin High School
Section Two: Proteins
The Chemistry of Proteins: Answer the following questions in the spaces provided. You may need to refer to your notes or
your text book in order to properly answer these questions
1. What is a Protein?
2. Define the following terms:
(a) Amino Acid
(b) Monopeptide
(c) Polypeptide
3. How do you draw the following:
Monopeptide, Polypeptide
Biology 30S Name:
Digestion and Nutrition
Kelvin High School
4. How is a Polypeptide assembled from Monopeptides?
The Task has been
completed satisfactorily
Biology 30S Name:
Digestion and Nutrition
Kelvin High School
Identification of Proteins:
Materials:
Droppers test tubes test tube racks
Ceramic Spot Plate Nitric Acid Biuret’s Reagent
Grease pencils fingernail clippings egg white (hard boiled)
Absorbent cotton dog hair cream cheese
Procedure #3: Xanthoproteic Test
The Xanthoproteic Test is used to identify Proteins. The term Xanthoproteic is Latin in origin and is
derived from the words “xantho” (which means yellow) and “proteic” (which means protein). If a
substance turns yellow during this test it is a protein.
1. Get a clean Ceramic Spot Plate
2. Using the diagram below as a guide, add a small amount of each of the following substances
to a separate well on the spot tray
Well #1 – fingernail clippings
Well #2 – egg white (hard boiled)
Well #3 – absorbent cotton
Well #4 – dog hair
Well #5 – cream cheese
3. Add 5 drops of Nitric Acid to each well
4. Wait for 30 seconds and then observe the wells and record your results in the Xanthoproteic
Test Results column of Table #4
Well #1
Fingernail
clippings
Well #2
Egg White Well #3
Cotton
Well #4
Dog Hair
Well #5
Cream
Cheese
Biology 30S Name:
Digestion and Nutrition
Kelvin High School
Procedure #4: Biuret’s Test The Biuret’s Test is another test use to identify proteins. Biuret’s reagent will react with protein
molecules after a short period of time. (Will eventually turn Purple)
1. Get a clean Ceramic Spot Plate
2. Using the diagram below as a guide, add a small amount of each of the following substances
to a separate well on the spot tray
Well #1 – fingernail clippings
Well #2 – egg white (hard boiled)
Well #3 – absorbent cotton
Well #4 – dog hair
Well #5 – cream cheese
3. Add 5 drops of Biuret’s Reagent to each well
4. Wait for 5 minutes and then observe the wells and record your results in the Biuret’s Test
Results column of Table #4
Table #4: Identifying Proteins
Substance Xanthroproteic
Test Results
Biuret’s
Test Results
Is the Substance
a Protein?
(Yes or No)
Fingernail Turns yellow Turns Purple
Egg White Turns yellow Turns Purple
Cotton No change No change
Dog Hair Turns yellow Hard to tell
Cream Cheese Turns Yellow Turns Purple
The Task has been
completed satisfactorily
Well #1
Fingernail
clippings
Well #2
Egg White Well #3
Cotton
Well #4
Dog Hair
Well #5
Cream Cheese
Biology 30S Name:
Digestion and Nutrition
Kelvin High School
Section Three: Lipids and Fats
The Chemistry of Lipids and Fats: Answer the following questions in the spaces provided. You may need to refer to your notes or
your text book in order to properly answer these questions
1. What is a Lipid?
2. What is a Fat?
3. Define the following terms:
(a) Fatty Acid
(b) Glycerol
(c) Monoglyceride
(d) Triglyceride
(e) Saturated Fat
(f) Unsaturated Fat
4. What is a unique characteristic of Fat Polymers that are not shared by other Polymers?
Biology 30S Name:
Digestion and Nutrition
Kelvin High School
5. How do you draw the following:
Fatty Acid, Glycerol, Triglyceride
6. How is a Triglyceride assembled from Glycerol and Fatty Acids?
The Task has been
completed satisfactorily
Biology 30S Name:
Digestion and Nutrition
Kelvin High School
Identification of Fats (Lipids):
Materials:
Grease pencils Test tubes test tube rack
Eye dropper distilled water brown paper
Lighter fluid oil (canola, olive) test tube stoppers
Unknown Substances X,Y and Z
Procedure #5: Solubility Test on Known Fats
Generally speaking, Fats (lipids) tend to be oils or semi solids. Fats are useful in that they can
store energy and some vitamins and nutrients. An object is considered soluble in water if it
completely disappears or is evenly mixed when added to water. An object is considered
insoluble in water if it is unable to mix with water when it is added. The following is a solubility
test of a known fat – oil.
1. Get two clean test tubes and label them one and two with a grease pencil
2. Add 10 drops of oil to each tube
3. Add 20 drops of lighter fluid to tube #1
4. Add 20 drops of cold water to tube #2. Use the diagram below as a guide:
5. Place a stopper on the end of each tube. Place your thumb over the stopper and shake
each tube for one minute
6. Wait one minute
7. Examine and compare both tubes. Record your results in Table #5
Biology 30S Name:
Digestion and Nutrition
Kelvin High School
Procedure #6: Brown Paper Test for Fats
This is another easy test used to identify Fats. An interesting thing happens when fats are rubbed
against brown paper.
1. On separate pieces of brown paper, rub one drop of oil (a fat) and one drop of water (not a
fat)
2. Allow the paper to dry for a few minutes
3. Hold the paper toward light. If light passes through, a translucent (semitransparent) spot
has formed.
4. Examine the pieces of paper to check for a translucent spot. Record your results in Table #5
Table #5: Results of Tests on Known Fats
Test Results
Fat Mixed with Lighter Fluid Soluble
Fat mixed with Cold Water Insoluble
Fat Rubbed on Brown Paper Forms clear spot
Water Rubbed on Brown Paper No noticeable change
The Task has been
completed satisfactorily
Biology 30S Name:
Digestion and Nutrition
Kelvin High School
Procedure #7: Testing Unknown Substances for Fats
1. Get three clean test tubes and label them X, Y and Z with a grease pencil
2. Place a SMALL amount of Unknown Substance X into the tube labelled X
3. Place a SMALL amount of Unknown Substance Y into the tube labelled Y
4. Place a SMALL amount of Unknown Substance Z into the tube labelled Z
5. Add 20 drops of water to each tube
6. Cover each tube with a stopper. Place your thumb on the stopper and shake each tube for
one minute.
7. Examine the tubes and record your results in Table #6
8. Repeat steps #1 - #4 9. Add 20 drops of lighter fluid to each tube
10. Cover each tube with a stopper. Place your thumb on the stopper and shake each tube for
one minute.
11. Examine the tubes and record your results in Table #6
Table #6: Testing Unknown Substances for Fat
Substance Soluble in
Water
Soluble in
Lighter Fluid
Translucent Spot
Formed on
Brown Paper
Fat Present?
X yes
yes
yes
Y no
yes
yes
Z no
no
sort of
The Task has been
completed satisfactorily
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