CarbohydratesCarbohydrates

• 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 6CO2 + 6H2O + energy C6H12O6 + 602

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 6H12O6 + 602 6CO2 + 6H20 + 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.

Carbohydrate Formula

Glucose C6H12O6

Fructose C6H12O6

Maltose C12H22O11

Sucrose C12H22O11

Starch• Starch is a natural condensation polymer

made of many glucose molecules linked together.

• The structure of glucose can be represented as:

H O HG

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 glucose6 12 6 2 6 12 6(C H O ) + H O C H On n n

Enzymes• Body enzymes function best at body

temperature (37oC) and are destroyed at higher temperatures.