Monosaccharides, disaccharides and polysaccharides Carbohydrates Monosaccharides, disaccharides and polysaccharides

Uses of glucose Glucose is important as a fuel (it is oxidised to release energy during respiration). Form in which carbohydrates are transported around the body (small and soluble). Important as a building block for building bigger carbohydrates such as starch, cellulose, glycogen. Converted into proteins and fats in plants.

Carbohydrates Carbohydrates are made up of C, H and O atoms. There are usually twice as many H as there are C and O with a ratio of 1C:2H:1C E.g. C6H12O6 or C5H10O5 Carbohydrates can be described as monosaccharides, disaccharides or polysaccharides.

Alpha Glucose – a monosacharide

Monosaccharides

Galactose

Disaccharide

Disaccharides (have a look at their structure on p Disaccharides (have a look at their structure on p.10 of J and J or online) glucose + a glucose → maltose glucose + fructose → sucrose galactose + glucose → lactose

Formation of Sucrose One glucose and one fructose molecule join together in a condensation reaction. Look at the dotted circle. Why is it called a condensation reaction? Sucrose

Condensation reactions These occur when a molecule of water is lost. Two monosaccharides join in a condensation reaction to form a disaccharide. A glycosidic bond forms between the two molecules. The opposite of this would be a hydrolysis reaction involving the addition of water and the splitting of the two molecules.

Polysaccharides Fgdjhgdliugpisrglkdnkgjdf;gjfdskl;gjklfdjgfdnglkfdgnlkfdjgkfldghlkdfhglkdfhgkdfj;glk;dfkg;ldfkg;dkfg;lfdk;lgdkfg’dfkg’lfdkglfkg;lkf;glkfdg;lfkg;lfkg;lfkg;lfkg;lfkg;lfgk;flgkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk Many monosaccharides joined together by condensation reactions.

Maths in biology 10% of the marks in A level biology are maths! You need to practise mathematical skills throughout the course. Attention to detail (correct units, unit conversions) and checking answers really helps. Developing the idea of ‘does it seem right?’ will help. Eg if you have calculated a human heart rate to be 56,000, have you gone wrong?

Helpful hints % change = Convervsions 1kg =1000g 1g = 1000mg 1mg = 1000µg 1l = 1000ml % change = change in value X 100 original value or (new value – original value) X 100

Questions Which one or more monosaccharides make up each of the following carbohydrates? Lactose Sucrose Starch 2. What type of bond is formed when a disaccharide is produced? 3. Glucose (C6H12O6) combines with fructose (C6H12O6) to form the disaccharide sucrose. From your knowledge of how disaccharides form, work out the formula of sucrose.