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B3: ORGANISATION AND THE DIGESTIVE SYSTEM (Catalysts and Enzymes (Enzyme…
B3: ORGANISATION AND THE DIGESTIVE SYSTEM
Tissues and Organs
Organs are collections of tissues performing specific functions
eg. muscular tissue to churn the food and digestive juices of the stomach together
eg. glandular tissue to produce the digestive juices that break down food
Organs are organised into organ systems, which work together to form organisms
eg. the digestive system
eg. the respiratory system
A tissue is a group of cells with similar structure and function
eg. glandular tissue, which contain secretory cells that can produce and release substances such as enzymes and hormones
eg. epithelial tissue covers the outside of the body as well as the internal organs
The Digestive System
The digestive system in a mammal is an organ system where several organs work together to digest and absorb food
How Does It Work?
Digestive enzymes are produced by specialised cells in glands and in the lining of the digestive system
Carbohydrase 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
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
Making Digestion Efficient
The enzymes made in the pancreas and the small intestine (amylase, protease and lipase) work best in alkaline (high pH) conditions
Bile is produced by the liver, stored in the gall bladder, and released through the bile duct. It neutralises acid and emulsifies fats
The protease enzymes of the stomach work best in acid conditions. The stomach produces hydrochloric acid, which maintains a low pH
The Chemistry of Food
Carbohydrates are made up of units of sugar
Simple sugars are carbohydrates that contain only one or two sugar units eg. glucose
Complex carbohydrates contain long chains of simple sugar units bonded together eg. starch
Lipids (fats and oils) consist of three molecules of fatty acids bonded to a molecule of glycerol
Protein molecules are made up if long chains of amino acids
They are enzymes, which are biological catalysts
They are antibodies, which destroy pathogens and are part of the immune system
They are hormones such as insulin
They are structural components of tissues such as muscles and tendons
Food Testing
Proteins
Biuret Test
(for protein)
Positive result = Biuret reagent turns purple
Lipids
Ethanol Test
(for lipids)
Positive result = Ethanol gives a cloudy white layer
Carbohydrates
Iodine Test
(for starch)
Positive result = solution turns blue or black
Benedict's Test
(for sugars)
Positive result = solution turns brick red upon heating
Catalysts and Enzymes
Enzymes are biological catalysts and catalyse specific reactions in living organisms due to the shape of their active sites (Lock and Key theory)
Enzymes are proteins. The amino acid chains are folded to form the active site, which matches the shape of a specific substrate molecule
Catalysts increase the rate of chemical reactions without changing chemically themselves
The substrate binds to the active site and the reaction is catalysed by the enzyme
Metabolism is the sum of all the reaction in a cell or the body
Enzyme activity is affected by temperature and pH
High temperatures denature the enzyme, changing the active site
pH can affect the shape of the active site of an enzyme and make it work very efficiently or stop it working