Nutrients
- 1. Nutrients
- 2. • List the chemical elements which make up carbohydrates, fats and proteins (Pure) • Describe and carry out tests for starch, reducing sugars, proteins and fats • State that large molecules are synthesised from smaller basic units • State the roles of water in living organisms Learning Outcome
- 3. What is in the food we eat?
- 4. What are the different Nutrients? Carbohydrates Proteins Fats Water
- 5. Carbohydrates Fructose Glucose Sucrose These are some examples of carbohydrates. What do they all have in common? Starch
- 6. General formula: CnH2nOn •Mono : 1 Monosaccharides • Eg: Glucose, fructose, galactose •Di : 2 Disaccharides • Eg: Maltose, sucrose, lactose •Poly : Many Polysaccharides Carbohydrates
- 7. Monosaccharides (Single sugar) Single sugar Occurrence Glucose Fructose Galactose Found in all animals Common in plants, but rare in animals Present in milk sugar from mammals
- 8. Disaccharides (Double Sugars) Double sugars Occurrence Maltose Sucrose Lactose Found in cereal Found in cane sugar (common table sugar) Present in milk sugar from mammals
- 9. Polysaccharides Many smaller basic units of glucose joined together to form polysaccharides.
- 10. Polysaccharides (Complex Sugars) Complex sugars Occurrence Starch Storage form of carbohydrate in plants Glycogen •Storage form of carbohydrate in animals •Stored mainly in liver and muscles Cellulose Structural form of carbohydrate in plants
- 12. • Can starch diffuse through the partially permeable membrane? • Can glucose diffuse through the partially permeable membrane?
- 13. Permeability • Monosaccharides are small sugar molecules that can pass through the visking tubing. • Disaccharides and polysaccharides are large, complex molecules that CANNOT pass through the visking tubing.
- 14. Testing for Reducing Sugars (Benedict’s Test) About 2cm3 of test solution (In this case: reducing sugars e.g. glucose) Heat in water bath Brick- Red precipitate Add an equal amount of Benedict’s solution
- 15. Benedict’s Test for Reducing Sugar Step 1: Add 2cm³ of Benedict’s solution to 2cm³ of sample. Shake well to mix. Step 2: Place test tube in a water bath containing boiling water for 5 mins. Step 3: Observe the change in colour and record your observations.
- 16. Benedict’s Test for Reducing Sugar Colour Change Conclusion Remains blue Reducing sugar absent Blue to brick-red precipitate Reducing sugar PRESENT
- 17. Benedict’s Test : can be used to find out the amount of reducing sugar Brick- red ppt Orange red ppt Green / yellow ppt Blue solution None Traces of reducing sugar Moderate Large amount of reducing sugar
- 18. Benedict’s Test Results Brick- red ppt Orange red ppt Green / yellow ppt Blue solution
- 19. Iodine test for Starch Step 1: Add a few drops of iodine solution to sample on a white tile (note: iodine solution = iodine + potassium iodide solution) Step 2: Observe and record your observations. Colour Change Conclusion Remains brown Starch absent Brown to blue-black colour Starch PRESENT
- 21. Fats / Lipids (Pure) • Organic compounds made up of carbon, hydrogen and oxygen. • No general formula for fats. • Found in butter, cheese, fatty meat, nuts, oil etc.
- 22. Fats Formed from smaller basic units of fatty acids and glycerol.
- 23. Oil droplet Add 2cm3 of ethanol Add 2cm3 of water Shake mixture thoroughly White emulsion 2 layers of immiscible liquid Test for oil/ fats Ethanol/ Alcohol Emulsion test
- 24. Ethanol Emulsion Test For liquid food: Step 1: Add 2cm3 of ethanol to a few drops of the sample. Shake the mixture well for about 5 mins. Step 2: Add 2cm3 of water to the mixture and shake it. Step 3: Observe and record observations. Observation Conclusion Solution remains clear Fats absent Cloudy white emulsion Fats PRESENT
- 25. For solid food: Step 1: Cut the sample into small pieces and place the pieces in a test tube. Step 2: 2cm3 of ethanol is added. Shake well for 5 mins. Step 3: Allow the solid particles to settle. Step 4: Decant ethanol portion to another test tube containing 2cm3 of water. Solid particles Ethanol Only pour off the top layer of ethanol
- 27. Proteins • Organic substances made up of carbon, hydrogen, oxygen and nitrogen • Sulfur may also be present
- 28. Proteins are built from…. Proteins are built up from smaller basic units of amino acids Many amino acids linked together to form Polypeptide / peptone.
- 29. Polypeptide Folding of this long chain of amino acids to give a unique three-dimensional shape Protein is formed From Polypeptides Proteins
- 30. Sample to be tested: in this case, Egg white (2cm3) Add 1cm3 of NaOH Add 1% CuSO4 drop by drop Shake mixture thoroughly Shake after each drop Allow mixture to stand for 5min Violet colour click Testing for Proteins (Biuret test) – 1st method
- 31. Step 1: Add 1 cm3 of sodium hydroxide solution to 2 cm3 of sample. Shake well. Step 2: Add 1% copper(II) sulfate solution, drop by drop, gently shaking after each drop Step 3: Observe and record observations Colour Change Conclusion Remains blue Proteins absent blue to violet Proteins PRESENT Testing for Proteins (Biuret test) – 1st method
- 32. Test for Proteins (Biuret test) – 2nd method Sample to be tested: in this case, Egg white (2cm3) Add 2cm3 of Biuret solution Shake mixture well Allow mixture to stand for 5min Violet colour
- 33. Biuret Test for Proteins (2nd Method) Biuret solution = sodium hydroxide + copper(II) sulphate solution Step 1: Add 2 cm3 of Biuret solution to 2 cm3 of the sample. Shake well. Step 2:Observe and record observations after 5 minutes. Colour Change Conclusion Remains blue Proteins absent blue to violet Proteins PRESENT
- 34. Summary
- 35. Based on these results, which one of the following conclusions about the food is correct? Micro Ques 1 ( D ) Proteins Reducing Sugars Starch A Absent Absent Absent B Absent Absent Present C Absent Present Absent D Present Absent Present
- 36. The table below shows the chemical elements present in each of the four substances. Which substance, A, B, C or D could be a protein? Micro Ques 2 ( C ) Substance Carbon Hydrogen Nitrogen Oxygen A B C D
- 37. Milk produces a red precipitate when heated with Benedict's solution. A purple colour develops when the biuret test is used on milk. Using these results only, which nutrients does milk contain? Micro Ques 3 ( C ) A Fat and protein B Fat and starch C Reducing sugar and protein D Reducing sugar and starch
Editor's Notes
- #2: Benedict's reagent and Fehling's solution are used to test for the presence of a reducing sugar. The reducing sugar reduces copper(II) ions in these test solutions to copper(I), which then forms a brick red copper(I) oxide precipitate. 3,5-Dinitrosalicylic acid is another test reagent that allows quantitative spectrophotometric measurement of the amount of reducing sugar present.
- #15: https://www.youtube.com/watch?v=TDFbtEwbmz0
- #17: The chemical reaction that makes Benedict’s solution turn from blue to red is a reduction of the Cu2+ ion by the various sugars to Cu2O which then precipitates. Cuprous Oxide is a reddish brown powder which is mostly insoluble in water. As larger amounts of the oxide are formed, the blue of the aqueous ion Cu2+(H2O)4 is decreased forming nice color sequence. When you have finally used up all of the Cu2+ ions, the solution will look a dirty red brown from the copper oxide suspended in the sugar, base, and leftover reagents.
- #25: emulsion test is a method to determine the presence of lipids using wet chemistry. The procedure is for the sample to be suspended in ethanol, allowing lipids present to dissolve (lipids are soluble in alcohols). The liquid (alcohol with dissolved fat) is then decanted into water. Since lipids do not dissolve in water, when the ethanol is diluted, it falls out of solution to give a cloudy white emulsion
- #27: characterized by edema, irritability, anorexia, ulcerating dermatoses, and an enlarged liver with fatty infiltrates oteins, mainly albumin, are responsible for creating the colloid osmotic pressure (COP) observed in the blood and tissue fluids. The difference in the COP of the blood and tissue is called the oncotic pressure. draw water back into the capillary by osmosis . This results in the pooling of fluids, causing the swelling and distention of the abdomen.[
- #30: Qn: what is the difference between polypeptide and protein?