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IB Macromolecule Model Building

Macromolecules make up a large group of organic compounds found in cells. They are generally used for energy, structure and support, signal recognition, pumps, and other functions.  Generally they consist of atoms of carbon, hydrogen,oxygen, and nitrogen.

 

With this lab exercise you will construct three groups of carbohydrates (monosaccharides, disaccharides and polysaccharides) and a lipid.  You will also be able to distinguish differences in molecular and structural formulas.

 

CARBOHYDRATES

Single Sugars or Monosaccharides:

Directions:

  1. Select two of the monosaccharides below (glucose, fructose, galactose) and construct two different models.

 Glucose_Haworth.png

The model constructed represents the three-dimensional shape of the molecules.  They illustrate that individual molecules of carbohydrates do differ from one another in general structural shape even though their molecular formulas are the same.  They also will illustrate how it is possible for molecules to join together to form different carbohydrates.  Have your model checked by instructor.

Monosaccharide Questions:  

  1. How many atoms of carbon are there in each of the following molecules?
  1. Glucose:
  2. Fructose:
  3. Galactose:

  1. Write the molecular formulas for the following molecules:
  1. Glucose:

  1. Fructose:

  1. Galactose:

  1. Compare the number of hydrogen atoms to the number of oxygen atoms in each sugar.  What is the ratio of hydrogen to oxygen (how many hydrogen atoms for each oxygen atom)?  
  1. Glucose:
  2. Fructose:
  3. Galactose: 

  1. How does the previous ratio compare to the ratio of hydrogen and oxygen atoms in water?

  1. Identify three examples of monosaccharides.

                                                                                 


Disaccharides:

Two monosaccharide molecules can chemically join together to form a large carbohydrate molecule called a double sugar, or disaccharide.  When a glucose molecule chemically joins with another glucose molecule, a double sugar known as maltose is formed.  When a glucose molecule joins with a fructose molecule, a different double sugar called sucrose is produced (There are no questions for this section).

Directions: 

  1. Join the two molecules you made in the first step to build a disaccharide molecule.
  2. Remove an –OH from one molecule and an –H end from another in order to join the molecules.
  3. Have your model checked by instructor.

Disaccharide Questions:  

  1. Compare the number of hydrogen atoms to the number of oxygen atoms in the disaccharide sugar.  What is the ratio of hydrogen to oxygen (how many hydrogen atoms for each oxygen atom)?  

  1. How does this ratio compare to a monosaccharide?

  1. What does the removal of the –OH and –H produce?

  1. List three examples of disaccharides.

Polysaccharides:

Just as double sugars were formed from two monosaccharide molecules, complex sugars are formed when many single sugars are joining together chemically.  The exact number of glucose molecules attached to form these polysaccharides is not known.  The two most common polysaccharides in biology are starch and cellulose.  They consist of long chains of glucose molecules joined together.

 

Directions:

  1. Construct a starch molecule by joining four glucose molecules (you will need to join with another group).  This represents only a small part of a starch molecule because starch consists of hundreds of glucose molecules.  Have your model checked by instructor.

Polysaccharide Questions:  

  1. Compare the number of hydrogen atoms to the number of oxygen atoms in the polysaccharide sugar.  What is the ratio of hydrogen to oxygen (how many hydrogen atoms for each oxygen atom)?  

  1. How does this ratio compare to a disaccharide and monosaccharide?

  1. List three examples of polysaccharides


Lipids:

Lipids are a group of carbon compounds that are insoluble in water (can’t be broken down by water).  Triglycerides are one of the primary groups of lipids and include adipose tissue in humans and oil in sunflower seeds.  Triglycerides are produced by the combination of three fatty acid tails and one glycerol molecule through dehydration synthesis.  Fatty acids can be saturated, monounsaturated or polyunsaturated.

triglyceride1.gif

Directions:

  1. Construct a glycerol molecule and three fatty acid tails, specifically a saturated, monounsaturated or polyunsaturated.

  1. Connect your triglyceride through dehydration synthesis.  Have your model checked by instructor.

 

Triglyceride Questions:

  1. Explain how unsaturated fatty acids can be cis or trans isomers.