Summary
Long chains of sugar units, including starch, glycogen, cellulose and chitin, used for storage and structure.
In depth
Starch (amylose plus branched amylopectin) is the plant store, glycogen is a more highly branched animal store, cellulose forms plant walls, and chitin forms fungal walls and arthropod exoskeletons. Branching gives many ends for rapid release of glucose.
Polysaccharides are insoluble or only slightly soluble and have little osmotic effect, making them ideal stores.
Amylose is an unbranched helix of alpha 1-4 glucose, while amylopectin has alpha 1-6 branches about every 25 residues; glycogen is branched every 8 to 12 residues, giving many free ends so that glucose can be released fast when needed. Compact storage polymers have little osmotic effect, unlike the same amount of free glucose, which would draw water into cells.
Other polysaccharides include pectin and hemicellulose in plant walls, inulin as a plant store, and glycosaminoglycans such as hyaluronic acid in connective tissue. Chitin has acetylated amino groups on each unit and is as strong as some synthetic polymers.
Example: a human liver can hold around 100 g of glycogen, enough to buffer blood glucose between meals.
Frequently asked questions
What is Polysaccharides?
Long chains of sugar units, including starch, glycogen, cellulose and chitin, used for storage and structure.
Which area of biology covers Polysaccharides, and how advanced is it?
Polysaccharides is one of the 51 topics in Biomolecules & Biochemistry. It is rated Beginner, so it suits learners who are starting out in biology. Related topics in this area include Carbohydrates, Starch vs Cellulose, Glycosidic Bond.
Can you give an example of Polysaccharides?
A marathon runner relies on glycogen in the muscles and liver, which runs low after about 90 minutes of hard exercise.
What should I learn before Polysaccharides?
Polysaccharides is a Beginner topic, so no earlier topic is required. Other Beginner topics in Biomolecules & Biochemistry that pair well with it include Water Properties, Carbon Chemistry, Carbohydrates.
What topics are related to Polysaccharides?
The closest topics to Polysaccharides are Carbohydrates, Starch vs Cellulose, Glycosidic Bond, ATP Structure and Function. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Polysaccharides?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Polysaccharides. To practise the whole of Biomolecules & Biochemistry, use the Biomolecules & Biochemistry quiz.
How is Polysaccharides different from Carbohydrates?
Polysaccharides: Long chains of sugar units, including starch, glycogen, cellulose and chitin, used for storage and structure. Carbohydrates: Sugars and starches built from carbon, hydrogen and oxygen that serve as fuel and structural material. Read both side by side and note what each one explains.
How should I study Polysaccharides step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Carbohydrates and explain the difference aloud. Finally, take the Biomolecules & Biochemistry quiz and come back to this page for any question you miss.