Functional groups in biopolymers

Image of a crabBiopolymers

Download worksheets for this activity here.

Lots of living creatures make polymers. These are sometimes called biopolymers.

Biopolymers can be extracted from living organisms. We use these extracted biopolymers in our everyday lives. e.g. Alginic acid (from seaweed) is used as a thickener in ice creams and is sometimes listed as E400 on ingredients lists.

Many biopolymers are polysaccharides, meaning they are made up of lots of sugar units. The sugar unit is a 6-membered ring, containing 5 carbon atoms and 1 oxygen. Different polysaccharides can have different functional groups on their sugar units. These give them unique properties.

How many different organic functional groups can you find on the following biopolymers?

structure of the cellulose molecule
Cellulose (from plants)


structure of the chitosan molecule
Chitosan (extracted from crustacean shells, e.g. crabs and lobsters)


structure of the alginate molecule
Alginic acid (extracted from seaweed)



Image credits

Brown crab by Perrine MARZIOU on Unsplash

Molecule structures – public domain by Zoe Schnepp

Back to top of page

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 International License.