CARBOHYDRATE LAB

Carbohydrates contain carbon (C), hydrogen (H), and oxygen (O). These are referred to as sugars or saccharides. The many different types of sugars have been grouped into three main categories: monosaccharides, disaccharides, and polysaccharides.

I. MONOSACCHARIDES

Examine the structural formulas and the corresponding models on your model sheet. We will use these paper models to illustrate the various types of carbohydrates and the chemical reactions necessary to join the molecules together.

1. What 3 elements are present in monosaccharides?

2. How many atoms of carbon are present in monosaccharides?

3. Write the molecular formula for glucose.

4. Write the molecular formula for fructose.

5. Write the molecular formula for galactose.

Compare the number of hydrogen atoms to the number of oxygen atoms in each sugar.

6. What is the ratio of hydrogen to oxygen in each sugar?

7. How do the ratios of hydrogen to oxygen compare in galactose, glucose, and fructose?

8. Is the arrangement of the hydrogen, oxygen and carbon molecules the

same in each sugar?

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II. DISACCHARIDES

Two monosaccharides molecules can join together chemically to form a disaccharide. By joining a glucose molecule with a fructose molecule, a different disaccharide called sucrose is formed.
CUT OUT A GLUCOSE AND A FRUCTOSE PAPER MODEL FROM YOUR MODEL SHEET. CUT THE MODEL ALONG SOLID LINES ONLY. ATTEMPT TO JOIN THE MOLECULES TOGETHER LIKE THE PIECES OF A PUZZLE.



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9. Will the two molecules stay together to form a sucrose molecule?

IN ORDER TO JOIN THESE TOGETHER LIKE PIECES OF A PUZZLE YOU MUST REMOVE AN –OH GROUP FROM ONE MOLECULE AND AN –H GROUP FROM THE OTHER CUT ALONG THE DOTTED LINES TO DO THIS. NOW THERE ARE TABS LIKE PUZZLE PIECES AND THE MOLECULES WILL FIT TOGETHER.


CONSTRUCT A MALTOSE MOLECULE BY JOINING TOGETHER THE 2 GLUCOSE MOLECULES. REMEMBER TO THE –H AND THE –OH ENDS.
10. Write the molecular formula for maltose.
11.
Write the molecular formula for sucrose.
12.
Is the ration of hydrogen to oxygen the same in sucrose and maltose?
13.
Is it the same in glucose and fructose?
14. How many monosaccharides are needed to construct a disaccharide molecule?

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III. Polysaccharides

Polysaccharides are formed from adding together many disaccharide molecules. The chemical reaction is the same one used informing disaccharides. Construct a portion of a polysaccharide by joining the remaining glucose molecules.
15.
What groups must you remove to form the tabs of the puzzle pieces?
16.
Is this the same reaction you used to form the disaccharides?
17.
Compare the ratio of hydrogen to oxygen in monosaccharides, disaccharides, and polysaccharides.


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