Carbohydrates

Carbohydrates contain Carbon (C), Hydrogen (H) and Oxygen (O). Carbohydrates include simple sugars such as glucose and fructose and more complex molecules such as starch, cellulose and glycogen. Carbohydrates are important sources of Energy

Carbohydrate Structure Monomer Dimer Trimer Polymer

Carbohydrates Carbohydrate monomers are called monosaccharides (single sugars). The most common monosaccharides are: Glucose, Fructose and Galactose All have the chemical formula C 6 H 12 O 6, They are all sweet tasting and soluble.

Glucose The most common monosaccharide. Glucose is the sugar most commonly used as an energy source in cellular respiration. It exists in two forms, alpha (α) and beta (β)glucose, which are isomers NB. You only need to know about α glucose for this module.

Structure of α glucose

Other Monosaccharides

Glycosidic Bonds Glycosidic bonds join two monosaccharide molecules together to form a disaccharide This is a condensation reaction - it involves the loss of one molecule of water Joining different monosaccharides together forms different sugars, e.g. –joining glucose + glucose = maltose

Complete the diagram in your booklet

Formation of Glycosidic Bonds Condensation Reaction

Important Disaccharides glucose + galactose = lactoseglucose + = maltoseglucose + fructose = sucrose

Get the structures from your booklets and: Hydrolyse the molecule sucrose to form glucose and fructose. Hydrolyse the molecule lactose to give glucose and galactose.

Polysaccharides Linking more monosaccharides together using glycosidic bonds creates long chains called polysaccharides Polysaccharides are insoluble storage molecules. They can be broken down into their monosaccharide monomers (by hydrolysis ie adding water back) to release energy as required.

Polysaccharide Disaccharide 2 x Monosaccharides condensation hydrolysis

Starch A mixture of two polymers of α- glucose Glycosidic bonds form between carbons 1 and 4 on the glucose molecules. A plant storage compound (e.g. potatoes)

Starch

Carbohydrate Digestion EnzymeWhere Produced Secreted Into SubstrateProduct Amylase Maltase Salivary Gland MouthStarch Maltose PancreasSmall Intestine StarchMaltose Small Intestine Maltose Glucose

Carbohydrate Digestion EnzymeWhere Produced Secreted Into SubstrateProduct Sucrase Lactase Small Intestine SucroseGlucose Fructose Small Intestine Lactose Glucose Galactose

Lactose Intolerance Read Page 25 in AQA text book What causes lactose intolerance? Why is it more common in recent times? What are the symptoms? How is it treated? How is possible calcium deficiency avoided in lactose intolerant people?