大分子 脂肪、蛋白质、糖(lipid, proteins, carbohydrates).ppt

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Energy Gained from Lipids Eating 1 gram of fat provides your body with 9 Calories. Notice if you eat 1 gram of fat, you are gaining more than twice the amount of Calories than from a gram of carbohydrate or protein! Nucleic acids The nucleic acids in food are not considered a substance that the body uses to gain energy. ENERGY So… BIG 4 MACROMOLECULES Number of Calories it provides Carbohydrates 4 Proteins 4 Lipids 9 Nucleic Acids 0 TEST: Are you smart? If you eat a sandwhich with 46 grams of carbs and 24 grams of protein and 10 grams of fat, how much energy will you gain? Simple tests can detect the presence of proteins, lipids and carbohydrates in given samples (i.e. various food items) Testing for carbohydrates Lugols reagent (iodine solution) Benedicts solution Testing for the presence of starch (complex sugar) Lugols reagent (iodine solution) changes from yellowish-brown to dark purple/black. Testing for simple carbohydrates Benedicts solution is used to test for simple carbohydrates. Benedicts solution is a blue colored liquid that contains copper ions. Testing for simple carbohydrates When Benedicts solution and simple carbohydrates are heated, the solution changes to orange red/ brick red. Testing for lipids Grease spot test/Brown paper test Sudan Red test Brown paper test for lipids As we all know from experience, lipids leave translucent spots (grease spots) on unglazed brown paper bags. Sudan Red test for lipids Sudan red is a fat-soluble dye that stains lipids red. Using Sudan red can show the amount and the location of lipids. Testing for proteins – Buiret test Buiret solution is a blue liquid that changes to purple when proteins are present and to pink in the presence of short chains of polypeptides. The copper atom of the biuret solution reacts with the peptide bonds to cause the color change. Testing for proteins – Buiret tes