Download Chemistry of Carbohydrates Name_____________ Prd.___

Chemistry of Carbohydrates
Name_____________
Prd.___Date_______
Part A: Carbohydrates
Biologists today depend upon chemists for much of their understanding of life and life
processes. Therefore, an understanding of some chemical concepts important to living things is
necessary. Organic compounds are those which contain the element ____________. Most are
made by living things, but some can be made in a laboratory.
Why is carbon such an important element in living things? Carbon atoms have ____ valence
electrons so they can form covalent bonds with as many as _____other atoms. Carbon atoms
can bond with each other to form ______________or _____________. The carbon atoms in
these chains and rings can also connect with atoms of other elements to form the basic units of
most biomolecules. Most biomolecules are polymers (“poly”=many; “mer”=unit) of smaller,
repeating units called __________________(“mono”=single or 1; “mer”=unit). There are 4 main
kinds of biomolecules: Carbohydrates, Lipids, Proteins, and _____________ ____________.
Carbohydrates are molecules that may also be called ________________. They are composed
of only 3 elements: _______, _______, and __________. The individual monomer units that
make up all carbohydrates are called _______________________________(“mono”=single or
1; “saccharis”= sugar).
Carbohydrates are important molecules for providing _______________for living organisms. In
addition, they play important structural roles for certain organisms. For example,
____________________is a complex carbohydrate (polysaccharide) that helps build the cell
walls of plant cells.
Part B: Monosaccharides or Single Sugars
The many different types of carbohydrates (or sugars) are grouped into 3 categories:
monosaccharides, disaccharides (“di”=2) or polysaccharides.
Examine the structural formulas and the corresponding models for the three monosaccharides.
The models do not show the exact 3-dimensional shape of the molecules but illustrate how
they differ from each other as well as how they join together.
1. What 3 elements are present in monosaccharides? ___________________
2. How many atoms of carbon are there in each of the monosaccharides?
a) Glucose __________
b) Galactose_________
c) Fructose__________
3. Write the molecular formulas for glucose, fructose and galactose by adding the proper
subscripts to each of the following:
a) Glucose C____H____O_____
b) Galactose C____H____O_____
c) Fructose C____H____O_____
4. Compare the number of hydrogen atoms to the number of oxygen atoms in each sugar.
What is the ratio of hydrogen to oxygen? (that is, how many hydrogen atoms are there
for each oxygen atom). _____________________
5. How do the ratios of hydrogen to oxygen compare in glucose, galactose, and
fructose?___________________
6. How do they compare to the ratio in water? _______________
7. Molecules may have the same molecular formula with identical numbers of atoms, yet
differ in their 3-dimensional shape. This is called ______________________. Describe an
example of isomerism in monosaccharides:
________________________________________________________________________
Part C: Disaccharides or Double Sugars
Two monosaccharide sugar molecules can join together chemically to form a larger
carbohydrate molecule called a __________________________, or double sugar.
By chemically joining a glucose molecule to another glucose molecule, a double sugar called
maltose is formed. By joining a glucose molecule with a fructose molecule, a double sugar
called sucrose is formed. By joining a glucose molecule with a galactose molecule, a double
sugar called lactose is formed.
Glucose + Glucose  ___________________(disaccharide)
Glucose + __________________  Sucrose (disaccharide)
Glucose + Galactose  __________________(disaccharide)
1. Attempt to join 2 paper models of glucose to form maltose. What must be removed
from each model in order to join them? ______________________________. Models
should fit together but will not join unless an OH end and an H end are removed.
2. What common molecule does an H atom combined with an OH group form?
__________________
3. This type of chemical reaction is called a _________________________
________________ reaction. (It may also be called a condensation reaction).
(“dehydrate”=to lose water; “synthesis”=to build something). Why is this a good name
for this type of reaction?
________________________________________________________________________
With your models, construct the following disaccharides: Maltose, Sucrose, and Lactose.
4. Carbohydrate molecules store energy in the bonds between the C, H, and O’s. Why is
there more stored energy in a Sucrose molecule than in a Glucose molecule?
________________________________________________________________________
5. Write the molecular formulas for each of the 3 disaccharides you built. Fill in the correct
subscripts for each: (Remember you lost a water molecule in order to join them)
Maltose C_____H_____O_____
Sucrose C_____H_____O_____
Lactose C_____H_____O_____
6. What is the H:O ratio of each of the disaccharides? _________:__________
7. Does isomerism exist in disaccharides? (Compare your paper models of the 3
disaccharides): _________
8. How many monosaccharide molecules are needed to construct one disaccharide
molecule? _________
Part D: Polysaccharides or Complex Carbohydrates
Just as double sugars were formed from two monosaccharide molecules, complex sugars or
__________________________are formed when many monosaccharides are joined together.
Starch and cellulose are two of the most common polysaccharides in biology. They consist of
long chains of glucose molecules bonded together.
Construct a starch molecule by joining three glucose molecules. Note: this will only represent
a small part of a starch molecule because starch actually consists of hundreds of glucose
molecules bonded together.
1. What must be removed from the glucose molecules in order to join them?
____________________What common molecule does this form? ____________
2. What type of chemical reaction joins these glucose molecules to each other?
_________________________________________
3. Determine the molecular formula of this small segment of starch. Fill in the proper
subscripts:
Starch: C_____H_____O_____
4. What is the H:O ratio in starch? ________:_________
5. How does this compare the ratios in the other carbohydrates we have studied?
__________________
Part E: Final Analysis
1. What 3 elements make up all carbohydrates?
_________________
_______________
_________________
2. What is the ratio between Hydrogen and Oxygen in all carbohydrates?
_________________
3. What is the name of the monomer units that make up all
carbohydrates? ________________________
4. What common molecule is always formed when monosaccharide
molecules are joined? ____________________
5. What kind of chemical reaction builds the larger carbohydrate
polymers? ___________________________________
6. “Mono” means 1, “di” means 2, and “poly” means many. Why are
these terms used to describe the three types of carbohydrates?
_____________________________________________________________
_____________________________________________________________
7. What is the primary function of carbohydrates in living organisms?
_____________________________________________________________