Form 4 - Biology Notes
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Biology Form 4 Notes (2003-2004)2005Jordan Mifsud (4.8) 5.8Page 1 BBiioollooggyy NNootteess FFoorrmm 44 T TO OP PI IC C 1 1: : N NU UT TR RI IT TI IO ON N The 7 Basic Food SubstancesAll the food we eat is made up of the following 7 basic substances: 1.Carbohydrates 2.Fats 3.Proteins 4.Vitamins 5.Minerals 6.Fibre 7.Water Carbohydrates,fats,proteinsandvitaminsareorganicsubstancesbecausethey containcarbonintheirmolecularstructure.Waterandmineralsareinorganic substances since they dont contain carbon.Carbohydrates,fatsandproteinsareneededinbulkinourdiet,whilevitaminsand minerals are needed in smaller amounts.A person whose diet lacks any of these nutrients suffers from malnutrition, and this may give rise to a deficiency disease.Foodgivesusenergy.Theamountofenergyneededbyourbodyisnt thesamefor everyone.Theamountofenergyneededtolivedependsonthepersonssex,job, attitude, age and other factors like if the person is a pregnant woman. 1.Carbohydrates Carbohydratesareorganicsubstancesmadeupofcarbon,hydrogenandoxygen. They are very important because they provide energy for the body. There are 3 types of carbohydrates: sugars, starch, and cellulose.A.Sugars Glucose (C6H12O6) Fructose (sugars in fruit) Sucrose (table sugar) Biology Form 4 Notes (2003-2004)2005Jordan Mifsud (4.8) 5.8Page 2 Glucose Molecule Lactose (found in milk) Maltose (found in barley grains) B.Strach Found in bread, potatoes, rice, cereals etc. Plants store food as starch. C.Cellulose Found in all unrefined plant food. An important source of fibre. Carbohydrates are all made up of molecules of glucose bonded (joined) together. The simplestformofcarbohydrateisglucose.Twomoleculesofglucosejoinedtogether withabond,formmaltose,lactoseandsucrosesugars.Starch,celluloseand glycogenareformedwhen3ormoreglucosemoleculesarejoinedtogetherwith bonds. Glucoses molecule is represented by a hexagon: A single sugar molecule is called a monosaccharide. Examples of monosaccharides are glucose and fructose. Sucrose,maltoseandlactosearealldisaccharidesbecausetheyhave2sugar molecules bonded together. Starch, cellulose and glycogen are all polysaccharides because they are made up of 3 or more sugar molecules bonded together. Biology Form 4 Notes (2003-2004)2005Jordan Mifsud (4.8) 5.8Page 3 Carbohydratesarefoundincereals,pasta,bread,fruit,potatoessugaryfoodsuchas ice cream etc. Glucoses chemical formula is the following: C6H12O6. Plantsstorefoodasstarch,whileanimalsstorefoodasglycogen.Bothglycogen and starch are polysaccharides. Polysaccharides are NOT sweet but ARE insoluble. 2.Fats Fats are organic substances. Lipids are fats in a liquid state. Fats are useful for our body, because they: provide energy,can be stored for later use,build up cell membranes,layers serve as an insulating layers under mammals skins andand oils on the surface of the skin makes the skin waterproof. Fat is found in vegetable oil, milk, fried foods, eggs, beef etc. Thesimplestfatmoleculeismadeupof1moleculeofglyceroland3fattyacids bonded together. Glycerol Fatty Acids Fatty Acids Fatty Acids Biology Form 4 Notes (2003-2004)2005Jordan Mifsud (4.8) 5.8Page 4 3.Proteins Proteinsareorganicsubstancesmadeupofhydrogen,carbonandoxygen, nitrogenandsometimestheycontainsulphur.Proteinsareneededbythebodyto growandrepairtissues(acellularstructure),theyarecomponentsofcell membranes, are used to produce enzymes (biological catalysts) and hormones.Thesimplestpossibleproteinisanaminoacid,thusproteinsaremadeupofamino acids, which can be represented as any form of shape (circle, rectangle, square). Aminoacidsarejoinedtogetherbypeptidebonds.When2aminoacidsconnected togetherwithapeptidebond,adipeptideforms.When3ormoreaminoacidsare joined together, a polypeptide is formed. Amino Acid Dipeptide Polypeptide Whenproteinsareheated,theyaredenatured;theychangeshape,itspropertiesand functions are destroyed. Food rich in proteins are milk, meat, eggs, nuts, fish etc. 4.Water Water is vital for animals and almost all living organisms. It makes up to one third of thehumanbodymass.Waterisaninorganicsubstancewiththechemicalformula H2O. Waterisimportantforanimalsbecauseitgivessupporttoaquaticanimals,gametes (sexcellslikespermsandeggs)travelinawaterymedium,sweatinghasacooling effect on the body, and urine and tears are mostly made up from water. There is water even inthejoints,so that reduces friction whenbonesmove. Even blood is partially made up of water. Waterisalsoneededbyplants,tomakeleavesturgid,guardcellsmovebyosmosis andwatertakespartinthechemicalreactioninwhichplantsmaketherefood(by photosynthesis). Some seeds germinate with the help of water. Biology Form 4 Notes (2003-2004)2005Jordan Mifsud (4.8) 5.8Page 5 5.Minerals Many minerals are important for our body. There are other trace elements not listed in the table which are useful for other bodily functions. MineralFound inUse in the bodyDeficiency disease Calcium Milk, cheese, fish, mineral water Developing bones and maintaining their rigidity. Forms intracellular cement and the cell membranes, and in regulating nervous excitability and muscular contraction. Rickets Iron Tomatoes, liver, kidneys Part of haemoglobin in red blood cells. Anaemia headaches, tiredness, and lethargy Phosphorous Many foods, e.g. milk Important for bones and teeth. Osteomalacia (rickets) Sodium Salt, many foods. Present in extra cellular fluid, and regulates it. Cramps Iodine Sea food, drinking water Needed to synthesize hormones of the thyroid gland. Goitre Fluorine Water, toothpaste Builds a layer above enamel. Can lead to tooth decay Magnesium Most foodsImportant for metabolism. Tremors and convulsions 6.Vitamins Vitamins are very, very important for the body, but only in small quantities.VitaminFound inUseDeficiency disease A Liver, carrotImportant for eyes.Night Blindness Exophthalmia. Biology Form 4 Notes (2003-2004)2005Jordan Mifsud (4.8) 5.8Page 6 D Fish liver oilHealthy bones and teeth. Rickets. E Milk, egg yolk, lettuce Healthy reproductive system. Sterility. K Cabbage, spinach, fish livers Important for the coagulation of blood. Disorders in blood clotting. B1 Pork, organ meats lean meats, eggs, leafy green vegetables, whole or enriched cereals, berries, nuts, and legumes. Catalyst in carbohydrate metabolism, enabling pyretic acid to be metabolised and carbohydrates to release their energy. Beriberi; Disturbances, impaired sensory perception, weakness, periods of irregular heartbeat, and partial paralysis. B2 Liver, milk, meat, dark green vegetables, whole grain and enriched cereals, pasta, bread, and mushrooms. Serves as a coenzyme-one that must combine with a portion of another enzyme to be effective-in the metabolism of carbohydrates, fats, and, especially, respiratory proteins. Skin lesions. Niacin (B6) Liver, poultry, meat, canned tuna and salmon. Works as a coenzyme in the release of energy from nutrients. Pellagra Diarrhoea, mental confusion, irritability, and, when the central nervous system is affected, depression and mental disturbances. C Citrus fruits, fresh strawberries, cantaloupe, pineapple, and guava. Important in the formation and maintenance of collagen, the protein that supports many body structures and Scurvy; Bleeding gums Biology Form 4 Notes (2003-2004)2005Jordan Mifsud (4.8) 5.8Page 7 plays a major role in the formation of bones and teeth. 7.Fibre Fibre is mainly cellulose from plant cell walls. Humans cannot digest fibre, but it is importantbecauseithelpsfoodtopassfromthegut,andpreventsconstipation. Food rich in fibre are whole meal bread, bran, cereals, fresh fruit and vegetables. Food Tests 1)TestforStarch:withIodinesolution.Ifresultispositive,ablue-black precipitate forms. 2)Test for Glucose: with Benedicts Solution and the mixture is heated. If the result is positive, an orange brown solution forms. 3)TestforProteins:withCopperSulphateandSodiumhydroxide.Apurple colour forms if the tested food contains proteins. 4)TestforFats:withEthanol(alcohol)Ammmiiilll kkkyyywwwhhhiiittteeesolutionformsin presence of fat. 5)TestforVitaminC:withDCPIP.Abluetoacccooolllooouuurrrllleeessssssliquidformsin presence of vitamin C. Biology Form 4 Notes (2003-2004)2005Jordan Mifsud (4.8) 5.8Page 8 Effect of Temp. on Enzymes012345610 20 30 40 50Temerature in degrees celciusmg of product per min.mg of products perminuteT TO OP PI IC C 2 2 E EN NZ ZY YM ME ES S Enzymesarebiologicalcatalysts.Acatalystenhancesthespeedofachemical reaction.Thus,enzymesarecatalysts,whichenhancethespeedofthechemical reactions taking place in the body. Properties of Enzymes Enzymesareproteins,therefore,theybecomedenaturedbyheat,whichmeansthat whenheatedabove40oC,theychangeshapeanddonotworkanymore.Whenthe temperatureislowerthannormal,enzymesbecomeinactive.Enzymesarespecific, whichmeansthateveryenzymecatalysisonlyonetypeoffoodsubstance,for example,theenzymeamylasecatalysisonlystarch,anddoesnottakepartinany other chemical reaction involving another food substance. Enzymesdonottakepartintheproperchemicalreactions(theydonotreact),they just enhance the speed, and this property makes them used over and over again. Anenzymecatalysisareactioninvolvingasubstrate;theparticularnutrientthe enzyme acts on. When the reaction is complete, a product is produced. An example is amylaseactingonstarch.Amylase,whichisanenzyme,actsonitssubstrate (starch), to produce a product (maltose), which is a simpler type of carbohydrate. The rate of productivity by enzymes is very affected by temperature and by pH. The graphshowstherateoftheactivitybytheenzymesinrelationtotemperature.The rate increases slowly when the temperature rises between 10oC to 40oC, but when the temperaturerisesfurther,activitydecreasedrastically,becauseenzymesarebeing denatured. Biology Form 4 Notes (2003-2004)2005Jordan Mifsud (4.8) 5.8Page 9 The graph here below shows the sensitivity of enzymes to pH. It is a bell-shaped graph, showing that the enzymes work best that at their optimum pH, which in this case is pH 2.