Question

activity c (continued from previous page)

1. summarize: now create a balanced equation for that shows the entire hydrolysis reaction. (in other words, the equation should show how the oligosaccharide broke up into three separate glucose molecules.)

turn on show current formula/equation to check your answer.

1. compare: how do hydrolysis reactions compare to dehydration synthesis reactions?
2. apply: amylose is a carbohydrate that consists of a single chain of hundreds of glucose molecules. consider an amylose molecule with only four glucose molecules.

a. how many water molecules are released when the 4 - glucose amylose forms?
b. what do you think is the chemical formula for this amylose?
c. how many water molecules would be needed to break this amylose down into four glucose molecules?

1. extend your thinking: hydrolysis of the carbohydrates you eat begins in your mouth as you chew. how do you think this process might be affected if a persons salivary glands were unable to produce saliva, which is mostly composed of water?

Explanation:

Step1: Write hydrolysis equation for oligosaccharide

An oligosaccharide with three glucose units can be considered as a trisaccharide. The general formula for a trisaccharide made of glucose monomers is $C_{18}H_{32}O_{16}$. Hydrolysis adds water ($H_2O$) to break the bonds. The balanced hydrolysis equation is $C_{18}H_{32}O_{16}+ 2H_2O
ightarrow3C_6H_{12}O_6$.

Step2: Compare hydrolysis and dehydration - synthesis

Hydrolysis reactions use water to break down larger molecules into smaller ones. Dehydration - synthesis reactions remove water to build larger molecules from smaller ones. They are opposite processes.

Step3: Calculate water molecules for amylose formation

When glucose molecules form amylose through dehydration - synthesis, for $n$ glucose molecules, the number of water molecules released is $n - 1$. For a 4 - glucose amylose ($n = 4$), the number of water molecules released is $4-1=3$.

Step4: Determine chemical formula of 4 - glucose amylose

The formula for glucose is $C_6H_{12}O_6$. For a 4 - glucose amylose, we start with $4\times C_6H_{12}O_6$ and subtract the 3 water molecules released during formation. The formula is $C_{24}H_{42}O_{21}$.

Step5: Calculate water molecules for amylose hydrolysis

The number of water molecules needed to break down an $n$ - glucose amylose into individual glucose molecules is the same as the number of water molecules released during its formation, which is $n - 1$. For a 4 - glucose amylose, 3 water molecules are needed.

Step6: Analyze saliva and carbohydrate hydrolysis

Saliva contains enzymes like amylase which catalyze the hydrolysis of carbohydrates. If salivary glands cannot produce saliva, the initial breakdown of carbohydrates in the mouth will be severely impaired as there will be no amylase and less water for the hydrolysis reaction to occur.

Answer:

1. $C_{18}H_{32}O_{16}+ 2H_2O

ightarrow3C_6H_{12}O_6$

1. Hydrolysis uses water to break down molecules; dehydration - synthesis removes water to build molecules. They are opposite processes.
2. A. 3

B. $C_{24}H_{42}O_{21}$
C. 3

1. The initial breakdown of carbohydrates in the mouth will be severely impaired as there will be no amylase and less water for hydrolysis.