Organisation and the Digestive System

Tissue and Organs

- a tissue is a group of cells with similar structure and function

- organs are collections of tissues performing specific functions

- organs are organised into organ systems, which work together to form organisms

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Human Digestive System

- organ systems are groups of organs taht perform specific functions in the body

- the digestive system in a mammal is an organ system where several organs work togteher to digest and asorb foodo

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Chemistry of Food

- carbohydrates are made up of units of sugar

- simple sugars are carbohydrates that contain only 1 or 2 sygar units- they turn into blue Benedict's solution brick read on heating

- complex carbohydrates contain long chains of simple sugar units bonded together,

    starch turns yellow- red

    iodine solution blue- black

- lipids consist of 3 molecules of fatty acids bonded to a molecule of glycerol, the ethanol test indicates the presence of lipids in solutions

- protein molecules are made up of long chains of amino acids, biuret reagent turns from blue to purple in the presence of proteins

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Catalysts and Enzymes

- catalysts increase the rate of chemical reactions without changing chemically themselves

- enzymes are biological catalysts and catalyse specific reactions in living organisms due to the shape of their active site, this is the lock and key theory of enzyme action

- enzymes are proteins, the amino acid chains are folded to form the active site, which matches the shape of a specific substrate molecule

- the substance binds to the active site and the reaction is catalysed by the enzyme

- metabolism is the sum of all the reactions in a cell or the body

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Factors Affecting Enzyme Action

- enzyme activity is affected my temperature and pH

- high temperatures denature the enzyme, changing the shape of the active site

- pH can affect the shape of the active site of an enzyme and make it wokr very efficiently or stop it working

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How the Digestive System Works

- digestion involves the breakdown of large insoluble molecules into soluble substances that can be absorbed into the blood across the wall of the small intestine

- digestive enymes are produced by specialised cells in glands and in the lining of the digestive system

- carbohydrates such as amylase catalyse the breakdown of carbohydrates to simple sugars

- proteases catalyse the breakdown of proteins to amino acids

- lipases catalyse the breakdown of lipids to fatty acids and glycerol

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Making Digestion Efficient

- the protease enzymes of the stomach work best in acid conditions, the stomach produces hydrochloric acid, which maintains a low pH

- the enzymes made up in the pancreas and the small intestine work best in alkaline conditions

- bile produced by the liver, stored in the gall bladder, and released through the bile duct neutralises acid and emulsifies fats

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