Polysaccharides are all polymers, which are very large molecules made up of simple sugars. They includes starches, glycogen, and cellulose. We’ll see how.

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Synthesis of PolysaccharidesPolysaccharides are all polymers, which are very large molecules made up of simple sugars. They includes starches, glycogen, and cellulose. Well see how these are produced, or synthesized. 1

Polysaccharides are made up of many smaller molecules called monomers joined together. One common monomer is (click) glucose

Glucose(a monosaccharide)monomer2

Glucose is a simple sugar or monosaccharide.

Glucose(a monosaccharide)monomer3

Two other common monosaccharides are (click) galactose and (click) fructose. You can see these all have slightly different shapes or structures.

Glucose

Galactose

Fructose4

A molecule of glucose contains 6 carbon atoms, (click) which are numbered like this.

Glucose(a monosaccharide)1234565

These two OH groups are used to bond glucose monomers to each other. Well see how that works.

glucose6

Here are two glucose units

glucoseglucose7

Well consider this OH on the first glucose molecule, and this (click) H on the second glucose molecule. An enzyme in plants enables two glucose molecules to join together. Lets have a look at this.

glucoseglucose8

We can imagine the H and the OH coming off and the two molecules moving together. We should point out here that the actual mechanism for this is much more complex and involves enzymes. The simplified animation here just helps us visualize how the two glucose monomers can bond together.

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When the two glucose units bond together, they form another sugar called maltose.

maltose(a disaccharide)10

Because maltose is a combination of two glucose monomers, it is called a double sugar or disaccharide.

maltose(a disaccharide)11

The H atom from one glucose, bonded to the OH from the other glucose, forms a molecule of water.

maltose(a disaccharide)water

12Because a larger molecule is made from two smaller molecules, this process is called (click) synthesis.

water

waterDehydrationSynthesis

13And because a water molecule is released, its called (click) dehydration synthesis.

water

DehydrationSynthesiswater

14Another disaccharide is formed when a molecule of (click) galactose and a molecule of (click) glucose

glucosegalactose

15Bond to each other in a dehydration synthesis to form lactose. Lactose is a common disaccharide found in milk products.

lactosewater16Still another disaccharide is formed when a molecule of (click) glucose and a molecule of (click) fructose

glucosefructose17Bond to each other with a dehydration synthesis to form sucrose, a common disaccharide found in table sugar.

water

sucrose18Now well go back to our molecule of maltose and see how we can add more glucose units to it to form a polysaccharide.

water

maltose19

More glucose molecules bond to this maltose and grow this chain by the process of dehydration synthesis.

20eventually forming starch

Starch consists of long chains of glucose molecules with some branching 21which consists of very long chains of glucose units

Starch consists of long chains of glucose molecules with some branching

22That have some branching. Starch molecules can consist of up to 4000 glucose units.

Starch consists of long chains of glucose molecules with some branching

23Glycogen is another polysaccharide. You can see it has a lot more branches than starch. It is produced in animals rather than in plants. When blood levels of glucose are high, the liver produces glycogen, which is a way of storing glucose for when it is needed. Glycogen is stored in the liver, and in muscle cells.

Glycogen consists of long chains of glucose molecules which are highly branched

24Like starch, glycogen also consists of long chains of glucose units.

Glycogen consists of long chains of glucose molecules which are highly branched

25But in glycogen, the chains are much more highly branched than in starch.

Glycogen consists of long chains of glucose molecules which are highly branched

26A different type of polysaccharide called Cellulose is produced in plants.

Cellulose consists of long chains of glucose molecules which are not branched

27Cellulose consists of long, unbranched chains of glucose units.

Cellulose consists of long chains of glucose molecules which are not branched

28Notice that the linkage between glucose units is different in cellulose than it is in starch or glycogen.

Cellulose consists of long chains of glucose molecules which are not branched

The linkage between glucose subunits is different in cellulose, than in starch or glycogen.29in cellulose, the oxygen atoms between the glucose units alternate their positions

Cellulose consists of long chains of glucose molecules which are not branched

The linkage between glucose subunits is different in cellulose, than in starch or glycogen.30whereas in starch and glycogen, the oxygen atoms between glucose units are all in the same relative positions.

Starch consists of long chains of glucose molecules with some branching

In starch and glycogen, the oxygen atoms between glucose subunits are all in the same relative positions.31It is important to note that the human body is capable of digesting starch and glycogen,

StarchGlycogenCelluloseThe human body is capable of digesting starch and glycogen, but NOT cellulose.32But it is NOT capable of digesting cellulose.

StarchGlycogenCelluloseThe human body is capable of digesting starch and glycogen, but NOT cellulose.33The body breaks down starches and glycogen in steps, eventually ending up with many single glucose molecules, which the body uses for energy.

StarchGlycogenCelluloseThe human body is capable of digesting starch and glycogen, but NOT cellulose.34Even though the polysaccharide cellulose is not broken down by the body, it provides the body with fiber, which is believed to help with digestion in the large intestine..

CelluloseCellulose provides the body with fiber, which helps with digestion.35Acknowledgements for Images Used

"Alpha-D-Glucopyranose" by NEUROtiker - Own work. Licensed under Public Domain via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Alpha-D-Glucopyranose.svg#/media/File:Alpha-D-Glucopyranose.svg

36Acknowledgements for Images Used

"Beta-D-Galactopyranose" by NEUROtiker - Own work. Licensed under Public Domain via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Beta-D-Galactopyranose.svg#/media/File:Beta-D-Galactopyranose.svg

37Acknowledgements for Images Used

"Beta-D-Fructofuranose" by NEUROtiker (talk contribs) - Own work. Licensed under Public Domain via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Beta-D Fructofuranose.svg#/media/File:Beta-D-Fructofuranose.svg

38Acknowledgements for Images Used

"Lactose Haworth" by NEUROtiker - Own work. Licensed under Public Domain via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Lactose_Haworth.svg#/media/File:Lactose_Haworth.svg39Acknowledgements for Images Used

"Saccharose2" by NEUROtiker - Own work. Licensed under Public Domain via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Saccharose2.svg#/media/File:Saccharose2.svg

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