Visit Your Local PBS Station PBS Home PBS Home Programs A-Z TV Schedules Watch Video Donate Shop PBS Search PBS
Scientific Frontiers Logo
TV Schedule
Alan Alda
For Educators
Previous Shows
Future Shows
Special Features

Losing It
  Teaching Guide

Activity 1: Grades 5-8
Tasty Models

Understanding the arrangement of atoms within nutrient molecules often helps explain their chemical behavior, health attributes and role in weight balance. Although atomic representations do not accurately represent electron configurations, they can be used to show the arrangement of nuclei and bond type. In the following activities, you'll construct several different molecular models that represent substances that play an essential role in our nutritional needs.


Image of molecule

Activity
Answers
Print version (PDF)
Main Menu
Help
 


This activity page will offer:

  • A hands-on experience in constructing models
  • A chance to visualize the atomic arrangements of nutrient molecules
  • An opportunity to apply critical thinking to atomic modeling

Glucose
Carbohydrates are a group of nutrients that include sugars and starches. The most familiar carbohydrate building block is probably glucose. Glucose is the basic "fuel" of living things. During the process of cellular respiration, glucose breaks down and releases the energy needed to maintain life processes.

Materials

  • Gum drops (variety of colors)
  • Toothpicks

Glucose Model

  1. Examine the supply of gumdrops that you will be using to assemble your molecular models. Now, consider the formula of glucose, C6H12O6. Based on this formula, how should you assign specific colors to the component atoms? (The most common color should be assigned to hydrogen, since hydrogen atoms are the most numerous.)
  2. To build the ring version of glucose, let's construct a closed ring formed by five carbon atoms and one oxygen atom.

    Graphic of glucose model


  3. Now, let's add the sixth carbon atom. It is attached to the ring carbon that is immediately to the left of the oxygen atom.

    Graphic of glucose model

  4. The remaining five oxygen atoms are part of hydroxyl (OH) groups. They are added as shown here

    Hydroxyl model
  5. Complete the model by adding the remaining seven hydrogen atoms so that each carbon atom forms four bonds.

    Final glucose model

Questions

  1. What does the 12 refer to in the chemical formula
  2. C6H12O6?
  3. How many total atoms are in one molecule of glucose?
  4. Write a balanced equation that illustrates the breakdown of glucose during aerobic respiration.

Protiens
Proteins are large molecules that are found in every living cell. Like carbohydrates, they compose a critical part of our diet. They are also the profiled nutrient in the Atkins diet. The basic building block of a protein molecule is an amino acid. All amino acids share a common feature. They contain both an amine (NH2) group and a carboxyl (COOH) group

Glycine Model

  1. Glycine is the simplest amino acid. Like all amino acids it has an amine,
  2. (NH2) group. Use gumdrops to construct this functional group.
  3. Like all amino acids, glycine also has a carboxyl (COOH) group. In this group, one of the oxygen atoms forms a double bond with the carbon atom. Use gumdrops to construct this functional group. Remember to retain consistency in your assignment of gumdrop colors.
  4. The amine and acid group are both attached to a central carbon atom. The remaining two bonds of this backbone carbon are saturated with hydrogen. Your finished glycine model should resemble this image.

    Glycine model

Questions

  1. What are amino acids?
  2. What are common features to all amino acids?
  3. Compare and contrast the composition of an amino acid to a sugar.

Finding Nutrients
What foods contain the highest percentages of carbohydrates, proteins and fats? Use Internet and print resources to uncover the common dietary sources for these nutrients. Does an individual's economic status effect the sources? Explain.

Computer Modeling
There are all sorts of computer molecular modeling programs on the Web. Many are free to use and offer powerful construction and manipulation tools. Check out some of these free tools at http://ep.llnl.gov/msds/dvc/viewrs.html.
For MACs running under OS X, iMOL is a powerful program that you can download it at http://www.pirx.com/iMol.

3D Models From a 2D Image
By "freeviewing" two side-by-side images, you can experience the stereoscopic illusion of depth. This technique is sometimes used by scientists to help illustrate three-dimensional layout of molecules. Check out this URL for some screen-popping examples of the freeviewing effect: http://valhalla.chem.udel.edu/3-D.html.

Web Connection

Nutrition Navigator
A comprehensive site maintained by Tufts University that offers a rating guide to nutrition websites
http://navigator.tufts.edu/family/

Specialized Diets
A reference to the biochemistry of various nutrients and diets.
http://reference.allrefer.com/encyclopedia/
N/nutritio-human-nutrition-specialized-diets.html

The Digestive System
An overview to the biology of digestion
http://health.yahoo.com/health/centers/digestive/20.html

Academic Advisors for this Guide:
Suzanne Panico, Science Teacher Mentor, Cambridge Public Schools, Cambridge, MA
Anne E. Jones, Science Department, Wayland Middle School, Wayland, MA
Gary Pinkall, Middle School Science Teacher, Great Bend Public Schools, Great Bend, KS
Cam Bennet Physics/Math Instructor Dauphin Regional Comprehensive Secondary School Dauphin, MB Canada

 

 

 
© 1990-2002 The Chedd-Angier Production Company, Inc. All rights reserved.
 

Counting DownDebunking the Low-Fat, No-Fat MythLosing Weight the Surgical WayHeavy Hormones?Weighing In Teaching guide Email scientists Watch Online Web links & more Contact Search Homepage