Activity A: Constructing Molecules of an Ecosystem
Introduction: Plants combine simple molecules, like the ones you will “build” in this
exercise, to produce complex organic molecules, the molecules of life. The organic
molecules synthesized by plants are utilized by the plants themselves, as well as the
fungi, animals, and bacteria of the ecosystem.
Constructing Models
Open your molecular model kit. The contents represent the following:
Symbol
Element
Representation
Quantity per kit
C
Carbon
Black balls
10
H
Hydrogen
Yellow balls
28
N
Nitrogen
Blue balls
2
O
Oxygen
Red balls
6
Wood pegs and springs can be used to represent covalent bonds.
I.
Building Water
Water is probably the best known chemical to any student and is very important to
biological life on this planet. Water constitutes over 50% of the weight of most plants
and animals. Additionally, water functions as the “universal solvent” and is
necessary for many chemical reactions.
Choose the appropriate wooden balls to construct a model of a water molecule.
Use a short wood peg to represent each covalent bond. Sketch your model in the
space below. Describe the shape of the water molecule.
II.
Building additional simple, but important molecules
1. Construct models of these simple molecules:
 ammonia - NH3
 carbon dioxide – CO2
 oxygen gas – O2
 methane – CH 4
Hints:
 Use short wood pegs for single covalent bonds
 Use 2 springs to represent a double covalent bond (each spring represents
one covalent bond)
2. Sketch each molecule in the space below and write its formula underneath:
ammonia
carbon dioxide
oxygen gas
methane
NH3
1. Which of these molecules are linear?
2. Which contain double covalent bonds?
III. Building Glucose, a simple sugar
Organic molecules, or molecules of life, are complex carbon-based molecules
which are found in and produced by living organisms. The main groups of organic
molecules are carbohydrates, proteins, lipids and nucleic acids. Organic compounds
always contain carbon and usually hydrogen and oxygen as well.
All eukaryotic life forms “burn” carbohydrates as fuel, using a process called
cellular respiration. Carbohydrates include both sugars and starches.
The most important simple sugar (a.k.a. “monosaccharide”) is glucose. All of
your body cells depend on the breakdown of glucose to release energy needed for cell
functions. Your brain is particularly sensitive to blood glucose levels. All plants,
animals, and fungi depend on glucose as fuel.
The formula for glucose is C6H1206
1. Construct a “backbone” or chain of 6 carbon atoms, covalently bonded together.
Use long pegs to represent covalent bonds between carbon atoms. (Long pegs will
keep your model from getting too “crowded”.)
2. Use your text to add the H and O atoms in the correct arrangement to your model.
A. One partner should construct a linear form of glucose.
B. One partner should construct a ring form of glucose.
C. One partner should construct an isomer of glucose. (fructose or galactose)
3. Sketch your group’s model of glucose in the linear form:
How does the linear model of glucose differ from the text representation?
If time permits, combine a model of glucose and a model of fructose to produce the
disaccharide (“double sugar”), sucrose. Sucrose is also known as table sugar. The
process used to join two simple sugars to form a double sugar is called dehydration
synthesis.
IV. Building amino acids (Optional)
Follow-up Questions:
1. Use your text to complete this chart:
Name of Molecule
Formula
Organism which
uses this
compound
Process in which
this compound is
used:
Water
Oxygen
Carbon dioxide
Ammonia
Glucose
2. Describe a use of methane by humans. What is methane commonly referred to?
4. List several characteristics and functions of carbohydrates:
5. How do plants produce glucose?
6. How do plants produce starch from glucose?
7. List several functions of proteins in living organisms:
8. Define monomer –
9. Define polymer -
10. What process do animals use to digest their food?