Biology B3


B3.1 tissues and organs

  • A tissue is a group of cells with similar structure and function.
  • Organs are made up of tissues.
  • Organs are organised into an organ system witch work together to create an organism.
  • Organ systems include the digestive system , circulatory system and gas exchange system. 
  • These systems have specialized organs in them so they can do thir job correctly and its more efficient. 

Three tissues;

  • Muscular tissue, can contract to bring about movment
  • glandular tissue, to produce substances such as enzymes or hormons 
  • Epithelial tissue, covers some parts of the body. 
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B3.2 The human digestive system

  • Organ systems are groups of organs that preform specific functions in the body.
  • The digestive system in a mammal is an organ system in which several organisms work together to digest and absorb food. 
  • Glands,such as the pancreas and salivat glands produce digestive juices containing enzymes. 

Human digestive system;

  • stomach-where digestion occurs
  • liver-produces bile
  • small intestine-digestion occurs 
  • large intesting-water is absorbedfrom undigested food
  • pancres-produce digestive juices
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B3.3 The chemistry of food

  • Carbohydratesare made up of units of sugar.
  • Simple sugars are carbohydrates only one of two sugar units they turn blue Benedicts solution turn brick red on heating.
  • Complex carbohydrates contain long chains of simple sugar units bonded together. Starch turns yellow-red iodine solution blue-black.
  • LIpids consist of three molecules of fatty acids bonded to to a molecule of glycerol. A cloudy white layer with the ethanol test inicates the presence of lipids in solutions.
  • Proteinmolecules are mode up of long chains of amino acids. Biuret reagent turns from blue to purple in the presents of protein.
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B3.4 Catalysts and enzymes

  • catalysts increase the rate of chemical reaction withouth changing themselfs.
  • Enzynes are biological catalysts. The catalyst specif reactions reactions in living organisms due to the shape of thier active site. This is the lock and key theory of enzymes reactions.
  • The substrate binds to the active site and the reaction is catalyst by the enzyme. 
  • Metabolism is the sum of all the reaction in a cell or in the body.
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B3.5 Factors affecting enzyme action

  • Enzyme activity is affected by temperature and pH.
  • High temperature denatures the enzyme, changing the shape of the active site.
  • pH can also affect the shape of the active site of an enztme and make it work very effeciently or stop it from working. 
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B3.6 How the digestive system works

  • Digestion involves the break down of large,insoluble molecules into soluable substances. these smaller molecules can then be absorbed into the blood across the wall of the small intestine.
  • Digestive enzymes are produced by specialised cells in glands and in the linning of the digestive system.
  • Carbohydrates such as amylase, catalyse the break downs of carbohydrates into simple sugars,
  • Protease catalyse the breakdown of proteins to amino acids.
  • Lipases catalyse the break down of lipids to fatty acids and glycerol. 
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B3.7 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 in the pancreas and the small intestine work best in alkaline conditions. 
  • Bile is produced in the liver , stored in the gall bladderand released through the bile duct . It nuetralises and emulsifies fats. 
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