IMAT 2011 Q43 [Polysaccharide]

What would be the chemical formula of a polysaccharide made up of five glucose monomers?

A. {C_6H_{12}O_6}
B. {C_{30}H_{52}O_{26}}
C. {C_{30}H_{60}O_{30}}
D. {C_5H_{10}O_5}
E. {(CH_{n-1}O)_2}

First of all, let’s read the question carefully and ask ourselves the exact thing we are in need to solve. Usually, short questions might look easy but can be tricky, so read them carefully.

What would be the chemical formula of a polysaccharide made up of five glucose monomers?

We are being asked to find the chemical formula of a polysaccharide made up SPECIFICALLY.

FIVE GLUCOSE MONOMERS

What can we use to find the answer? First, we must know the Glucose chemical formula, {C_6H_{12}O_6}. We have five monomers, so we might MISTAKENLY pick {C_{30}H_{60}O_{30}} because of {C_6H_{12}O_6} times 5? Absolutely NOT!

Connecting monomers into polymers (in this case, polysaccharides) involves a Dehydration, The LOSS of water molecule when combining two monomers into one.

How many water molecules are lost during this process? If five monomers are connected, four water molecules must lose: (X = monomer o = water)

XoXoXoXoX

So the correct answer is {C_{30}H_{52}O_{26}}, B.

{C_6H_{12}O_6} timse five minus four times {H_2O}

Which is 5 Glucose minus 4 {H_2O} (water)

The rest of the answers just don׳t fit. We must know the glucose formula and the dehydration process.