CARBOHYDRATES.CARBOHYDRATES.

WHAT ARE CARBOHYDRATES?WHAT ARE CARBOHYDRATES?

Carbohydrates include sugars, starches, Carbohydrates include sugars, starches, cellulose and glycogen.cellulose and glycogen.

Carbohydrates are needed for storage and Carbohydrates are needed for storage and liberation of energy.liberation of energy.

All carbohydrates contain the following All carbohydrates contain the following elements: carbonelements: carbon

hydrogenhydrogen

oxygenoxygen

The carbohydrate groups.The carbohydrate groups.

Carbohydrates can be divided up into three Carbohydrates can be divided up into three groups: groups:

Monosaccharide-”single sugars” eg glucose.Monosaccharide-”single sugars” eg glucose. Disaccharides –”double sugars” eg sucrose.Disaccharides –”double sugars” eg sucrose. Polysaccharides-”multiple sugars” eg starchPolysaccharides-”multiple sugars” eg starch Monosaccharide and disaccharides are sugars Monosaccharide and disaccharides are sugars

that are sweet and soluble.that are sweet and soluble. Polysaccharides are polymers that are not sweet Polysaccharides are polymers that are not sweet

or soluble.or soluble.

Monosaccharide.Monosaccharide.

The commonest Monosaccharide is glucose The commonest Monosaccharide is glucose which exists in two forms:which exists in two forms:αα glucose and glucose and ββ glucose.glucose.

How glucose molecules join How glucose molecules join together.together.

Two glucose molecules are linked by a condensation reaction. this results in the formation of a disaccharide called maltose. The two monosaccharides are linked by a glycosidic bond (c-o-c ) and the molecules share an oxygen atom. During the condensation reaction water is formed.

DisaccharidesDisaccharides

The common examples of these double sugars The common examples of these double sugars are maltose, sucrose and lactose.are maltose, sucrose and lactose.

Maltose is formed from two glucose molecules. It Maltose is formed from two glucose molecules. It is found in germinating seeds when starch is is found in germinating seeds when starch is broken down.broken down.

Sucrose is formed from glucose and fructose Sucrose is formed from glucose and fructose molecules. It is found in the phloem tubes in molecules. It is found in the phloem tubes in plants.plants.

Lactose is formed from glucose and galactose. It Lactose is formed from glucose and galactose. It is found in milk.is found in milk.

polysaccharidespolysaccharides

Polysaccharides are formed from thousands Polysaccharides are formed from thousands of glucose molecules and are classified as of glucose molecules and are classified as polymers.polymers.

There are three polysaccharides that need There are three polysaccharides that need to be studied:to be studied:

starchstarch

glycogenglycogen

cellulose.cellulose.

Starch.Starch.

Starch is the main storage material in plants. Starch is the main storage material in plants. starch is insoluble and compact , but it is easily starch is insoluble and compact , but it is easily available for use by the plant.available for use by the plant.

Starch consists of two compounds: Starch consists of two compounds:

1. amylose –this is made up of a single chain of 1. amylose –this is made up of a single chain of αα glucose molecules that form spirals.glucose molecules that form spirals.

2. amylopectin- this is made up of branched 2. amylopectin- this is made up of branched chains of chains of αα glucose. glucose.

Structure of starchStructure of starch

Amylose.Amylose.

amylose

Amylopectin.Amylopectin.

Glycogen.Glycogen.

Glycogen is the main storage carbohydrate Glycogen is the main storage carbohydrate in animals.in animals.

It has a similar structure to amylopectin, but It has a similar structure to amylopectin, but it has more branches.it has more branches.

It structure allows it to be quickly built up or It structure allows it to be quickly built up or broken down , matching the animals needs.broken down , matching the animals needs.

Structure of glycogen.Structure of glycogen.

Cellulose.Cellulose.

Cellulose forms the main part of the cell wall Cellulose forms the main part of the cell wall in plants cells.in plants cells.

Cellulose is made up of Cellulose is made up of ββ glucose glucose molecules.molecules.

The slight difference between The slight difference between αα and and ββ glucose molecules means that instead of a glucose molecules means that instead of a spiral, spiral, ββ glucose molecules form chains that glucose molecules form chains that are long and straight.are long and straight.

Structure of cellulose.Structure of cellulose.

Hydrogen bonds

Parallel chains of β glucose molecules.

The long straight chains lie parallel to each The long straight chains lie parallel to each other and hydrogen bonds form along the other and hydrogen bonds form along the length of the chain. length of the chain.

The individual cellulose chains are bound The individual cellulose chains are bound together to form strong fibrils. These fibrils together to form strong fibrils. These fibrils are glued together to form cell walls. are glued together to form cell walls.