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Ch. 5 - The Structure and Function of Large Biological Molecules
Chapter 5, Problem 6

The molecular formula for glucose is C6H12O6. What would be the molecular formula for a polymer made by linking ten glucose molecules together by dehydration reactions? a. C60H120O60 b. C60H102O51 c. C60H100O50 d. C60H111O51

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Understand the structure of glucose and the process of forming a polymer through dehydration reactions. Glucose is a monosaccharide with the formula C6H12O6. In dehydration reactions, a water molecule (H2O) is removed to link each glucose molecule together.
Calculate the total number of each atom in ten glucose molecules without any dehydration. This would be 10 x C6 = C60, 10 x H12 = H120, and 10 x O6 = O60.
Determine the number of water molecules (H2O) removed during the formation of the polymer. Since each linkage between two glucose molecules removes one water molecule, linking ten glucose molecules would remove nine water molecules.
Subtract the atoms in the removed water molecules from the total calculated in step 2. For nine water molecules, 9 x H2 = 18 hydrogens and 9 x O = 9 oxygens are removed. So, the new totals are H120 - 18 = H102 and O60 - 9 = O51.
The molecular formula for the polymer is therefore C60H102O51, which corresponds to option b.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Dehydration Reaction

A dehydration reaction, also known as a condensation reaction, is a chemical process where two molecules combine to form a larger molecule, releasing a water molecule in the process. In the context of glucose, when multiple glucose units link together, each bond formation results in the loss of a water molecule, which is crucial for understanding how polymers are formed from monomers.
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Polymer Formation

Polymers are large molecules made up of repeating structural units called monomers. In this case, glucose acts as the monomer, and when ten glucose molecules are linked through dehydration reactions, they form a polysaccharide. The molecular formula of the resulting polymer can be derived by considering the number of glucose units and the water molecules lost during the bonding process.
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Molecular Formula Calculation

The molecular formula of a compound indicates the number and type of atoms present. For a polymer formed from ten glucose molecules (C6H12O6), the initial total would be C60H120O60. However, since each dehydration reaction removes a water molecule (H2O), the final formula must account for the loss of water, leading to a different molecular formula for the polymer.
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