Carbohydrates

Carbohydrates are important food for animals. Carbohydrates contain the elements carbon, hydrogen and oxygen. There are two hydrogen atoms for each oxygen atom in carbohydrates

Photosynthesis Photosynthesis is the process by which plants make carbohydrates and oxygen from carbon dioxide and water, using light energy. Chlorophyll (the green colour in plants) is used to absorb the light energy.

Carbon dioxide + water + energy  glucose + oxygen 6CO 2 + 6H 2 O + energy  C 6 H 12 O

Respiration Respiration is the process by which animals AND plants obtain the supply of energy that they need for growth, movement, warmth etc. They obtain this energy by breaking down the carbohydrate, glucose, using oxygen: Glucose + oxygen  carbon dioxide + water + energy C 6 H 12 O  6CO 2 + 6H energy Carbohydrates supply the body with energy.

Carbohydrates can be split into two groups: –Sugars –Starches

Sugars Examples of sugars include glucose, fructose, maltose and sucrose (table sugar). Sugars are soluble in water. Sugars are carbohydrates with small molecules. Testing for Sugars (except sucrose) Blue Benedict’s solution turns orange/red when heated with glucose, fructose or maltose. CarbohydrateFormula GlucoseC 6 H 12 O 6 FructoseC 6 H 12 O 6 MaltoseC 12 H 22 O 11 SucroseC 12 H 22 O 11

Starch Starch is a natural condensation polymer made of many glucose molecules linked together. The structure of glucose can be represented as:

Digestion of Starch During digestion starch is hydrolysed to glucose which is carried by the blood stream to body cells. Hydrolysis Reaction: a reaction in which a large molecule is broken down into two or more smaller molecules by the action of water.

Many glucose molecules join together in the following way to form starch. Plants convert the glucose into starch for storing energy.

Starch can be hydrolysed by acid and by enzymes. Acid starch glucose

Enzymes Body enzymes function best at body temperature (37 o C) and are destroyed at higher temperatures.