Biology B3

• 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. 

• 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

• 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.

• 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.

• 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. 

• 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. 

• 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.