Download Constructing Models of Carbodydrates

Name: __________________________________
Period: ______ Date: _____________
Honors Biology
Constructing Molecular Models of Carbohydrates, Lipids and Proteins
Introduction:
Carbohydrates, lipids, proteins and nucleic acids are the four major groups of organic molecules found in living
organisms. This lab will focus on the chemical structure of carbohydrates, lipids and proteins. Most organic
compounds are large polymers constructed by linking smaller monomers together with the removal of water in a
process called dehydration synthesis. Each class of organic compound has is own polymer and monomer units.
The term polysaccharide describes carbohydrate polymers which are constructed by linking monomers called
monosaccharides together. The term triglyceride describes lipid polymers such as fats and oils. Triglycerides
are constructed by linking two type of monomers; glycerol and fatty acids together. The term polypeptide
describes protein polymers. Polypeptides are constructed by linking monomers called amino acids together.
Purpose: The purpose of this lab is to identify the structural characteristics of carbohydrates, lipids and proteins,
construct models of carbohydrates, lipids and proteins, and model the process of dehydration synthesis.
Each pair of students should obtain a baggie of molecular model parts. The table below shows what each
component piece represents.
Component
Represents
4 prong black
Carbon atom
3 prong red
Nitrogen atom
2 prong blue
Oxygen atom
1 prong white
Hydrogen
atom
White tubes
Covalent bond
Part I: Water
The chemical formula of water is H20. Use the chemical formula of water to answer the following questions.
1. What elements make up water? _____ and ______
2.
What does the subscript number 2 following the H represent?
3.
Why doesn't the O have a subscript?
4.
How many molecules of water are represented by the formula H20? _______
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Build one molecule of water with the parts provided. Have your teacher check your model and
initial here: _________
5.
Draw the structural formula for water.
6.
What do the lines between O and H represent in your structural formula? (Specify the exact type in your
answer.)
Part II: Carbohydrates
The carbohydrate sugars (“saccharides”) are an important group of biological compounds. They contain
carbon (C), hydrogen (H), and oxygen (0). There is always a 2:1 ratio between the hydrogen and oxygen
in a carbohydrate. Carbohydrates also contain two important functional groups; the hydroxyl group (OH) and the carbonyl group (C=O). The carbonyl group is not present on the ring structures.
Carbohydrate sugars have been grouped into three main categories based on their size: monosaccharides,
disaccharides, and polysaccharides
The monosaccharide (single sugar) is the monomer unit of larger carbohydrates such as disaccharides
and polysaccharides. Monosaccharides usually have a five or six carbon backbone. Figure 1 shows the
structural formulas of three monosaccharides.
Figure 1
Figure 1 shows the structural formulas of three monosaccharides.
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Study the three different monosaccharides in figure 1. Answer the following questions.
1.
What elements are present in glucose, fructose, and galactose? ________, ________, _________
2. Write the chemical formulas for:
a. Glucose:
b. Fructose:
c. Galactose:
3. How are the structural formulas of glucose and galactose different from fructose? (Look at the shape of
the ring.)
4. How does the structural formula of glucose differ from galactose? (Your description should mention a
functional group.)
5. Compare the number of hydrogen atoms to the number of oxygen atoms in each sugar. What is the ratio of
hydrogen to oxygen? (i.e., how many hydrogen atoms are there for each oxygen atom?) REDUCE!
_________H: ________ O
6. What group is present on each monosaccharide?
7. Circle and label the functional group from your answer in the question above on one monosaccharide.
8. What functions does glucose serve? (There are two important ones! See table 3-2.)
Construct a three-dimensional model of glucose and fructose. Use figure 1 above as a guide to determine
how to arrange the atoms. Have your teacher check your models and initial below.
Teacher’s Initials: ___________
Dissaccharides are double sugars. They are constructed by dehydration synthesis. During this process, two
monosaccharides are bonded together by removing a molecule of water. A hydroxyl group from each
monosaccharide is involved. When a glucose and a fructose molecule are joined, the disaccharide sucrose is
produced.
Figure 2
Glucose
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Fructose
Sucrose
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Obtain your glucose and fructose molecules constructed earlier. Orient them the
same way as the figure above.
Remove the hydrogen atom from glucose and the hydroxyl group from fructose as
shown in the diagram above.
Bond the remaining oxygen on the glucose to the open carbon on fructose.
Join the remaining H and OH together.

Take your model up and have your teacher initial here: _____________________
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9.
What is the chemical formula of sucrose?
10. What did you remove to make sucrose? What is its chemical formula?
11. What is the ratio of hydrogen to oxygen atoms in sucrose? (Reduce!) ___ H : ___ O
12. How many monosaccharides are needed to form a disaccharide? How many water
molecules must be removed to form a disaccharide?
13. What is this process of linking monomers together by removing water called?
14. What functional group was involved in this process?
Completely disassemble your disaccharide and return all components to the baggie.
Part III: Lipids
Lipids include fats, oils, waxes, phospholipids and steroids. Fats and oil polymers are referred to as triglycerides.
They contain C,H and O, but they do not have a 2H:1O ratio. They usually have large amounts of C and H and
little O. The monomer units for fats and oils (triglycerides) are one glycerol + three fatty acids. Examine the
structural formula of glycerol and answer the following questions.
Figure 3
Glycerol
1. What elements are present in glycerol? ______, ________, ________
2. Are there any elements in glycerol that are not in carbohydrates? YES or NO
3. What is the chemical formula of glycerol?
4. Does glycerol have a 2H: 1O ratio like carbohydrates? YES or NO
5. What functional group is present on glycerol? __________
6. Circle and label the functional group identified in your answer above on glycerol. (You only need to circle
and label one of them.)
*** Construct a three dimensional model of glycerol. Use the picture of glycerol as a guide. Have your
teacher check your model and initial below. SAVE YOUR MODEL.
Teacher’s Initials: __________


The second portion of a triglyceride is a long carbon chain called a fatty acid. Many different fatty
acids exist, but all are similar in several ways.
Examine the structural formulas of the fatty acids and answer the following questions.
7. What elements are present in fatty acids? _____, ______, ______
8.
Do fatty acids have a 2 H: 1 O ratio? YES OR NO
9. What do you notice about the proportion of Carbon and Hydrogen compared to oxygen in fatty acids?
10. What two functional groups do all fatty acids have? _______ and _______
11. Circle and label each of the functional groups listed in your answer from the question above on each fatty
acid.
12. Are these fatty acids saturated or unsaturated? How can you tell in terms of their C-C bonds?
*** Construct three butyric acid models. (You need three because a triglyceride is composed of one glycerol
+ three fatty acids.) Have your teacher check your models and initial in the space below. SAVE ALL
THREE BUTYRIC ACID MODELS.
Teacher’s Initials: __________
A triglyceride molecule (a molecule of fat or oil) consists of one glycerol and three fatty acids.
Figure 5
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Obtain your glycerol and three butyric acid models from part III.
Place the glycerol on your lab station so the –OH groups are on the right side. Remove the hydrogen
from each –OH group on the glycerol (see Figure 5).
Place the butyric acids on the lab station. Find the carboxyl group on each butyric acid.
Remove the –OH end from each carboxyl group (see figure 5).
Connect each fatty acid to the glycerol (see Figure 5).
Join the H and OH’s together to make three water molecules
Have your teacher check your triglyceride and initial here: __________
13. What monomer units are needed to make a triglyceride? (Include appropriate number of each in your
answer.)
14. What process allowed you to construct the triglyceride? How many water molecules were removed?
15. Which two functional groups were involved in dehydration synthesis of the triglyceride?
Disassemble your triglyceride model.
Part IV: Proteins
Polypeptides (the polymer term for a protein) are composed of monomer units called amino acids. Examine the
structural formulas of the amino acids below and answer the following questions.
Figure 6
1. What elements are present in glycine, alanine and threonine? _____, _____, _____, _____
2. What element is present in amino acids that cannot be found in carbohydrates and lipids? ______
2. Every amino acid consists of a central carbon surrounded by an amino group, carboxyl group, and variable
group. Circle and label the central carbon, amino group, and carboxyl group on threonine. Circle
and label the variable group on the other two amino acids.
3. What other monomer unit has a carboxyl group? ___________
*** Construct a three dimensional model of glycine and alanine. Use the structural formulas in figure 6 as a
guide. Have your teacher check your model and initial in the space below.
Teacher’s Initials: ________
A protein consists of amino acids bonded together.
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Obtain your glycine and alanine.
To put them together, you will have to remove one molecule of water.
Remove the –OH from the carboxyl group on the glycine.
Remove one –H from the amino group on the alanine.
Connect the open positions on the carbon and nitrogen with a bond.
Join the H and –OH to make water.
Have your teacher check your protein and initial in the space below.
Teacher’s Initials: ________
The structure you just made is called a dipeptide because it is two amino acids long. The term polypeptide
or protein is reserved for chains of more than 50 amino acids.
4. How many molecules of water were removed to make a dipeptide? __________
5. What is this process called (removing water to link monomers together)? _______________________
6. Which functional groups on an amino acid are involved in the dehydration synthesis reaction?
7. Why isn’t the variable group involved in the dehydration synthesis reaction?
8. What is the name of the bond that forms between the two amino acids? ________________ What atoms
does it link? _________ and __________.
9. What is the monomer unit of a protein? ______________________
Disassemble your protein model and return all components to the baggies.
Conclusion:
10. Complete the following table for the three classes of organic compounds studied in this lab.
Organic Compound
Elements Present
Carbohydrate
Lipid
Protein
_____, _____, _____
_____, _____, _____
_____, _____, _____, _____
N/A
N/A
____________________
________________ +
________________
____________________
___________________
___________________
___________________
____________________
Don’t need to know a
specific example
Don’t need to know a specific
example
____________________
_______________________
Specific Element Ratio
_____: _____
Monomer Unit
Specific Example of
Monomer Unit
Polymer Unit
11. Name and describe the process in which all large polymers such as polysaccharides, triglycerides and
polypeptides are constructed?
12. Determine if the following are carbohydrates, lipids or proteins based on their chemical formulas:
C18H32O16
C4H8NO3
C21H38O6
13. Each diagram below represents a monomer unit for an organic compound class. Identify the name of the
monomer and the class of compound it belongs to.
Diagram
Name of Monomer
Class of Organic Compound