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All living organisms are composed of four classes of macromolecules:  Carbohydrates  Lipids  Proteins  Nucleic acid 2

 Carbon containing compounds are called organic compounds.  Carbon is the backbone of organic molecules, but its only one of several important bioelements.  These bioelements are hydrogen, nitrogen, oxygen, phosphorous and sulfur. 3

 The chemical properties of the different classes depend on the presence of specific functional groups:  Aldehyde group  Ketone group  Carboxyl group  Amino group 4

 Carbohydrates are the main energy storing molecules.  Monosaccharide : monomers (glucose, ribose, galactose).  Disaccharides: two monomers connected with glycosidic bond  (sucrose, lactose).  Polysaccharides: polymers; more than three monomers (starch). 5

A. Benedict’s test for reducing sugars:  The test depends on the presence of free Aldehyde or ketone group.  Monosaccharides and some disaccharides have these groups free are called reducing sugars.  Free groups found in reducing sugars will react with Benedict’s reagent (CuSo 4 which is blue in color with NaOH).  The test is both qualitative and quantitative test;  Small amount of reducing sugar  green color.  Large amount of reducing sugar  red- orange color. 6

7 Fill the test tubes with 1 ml of one of the following solutions. D.W glucose sucrose starch milk apple juice maltos e

8 Fill each test tube with 3 ml of Benedict’s reagent Put the test tubes in boiling water for 5 minutes If color change to: Record your results in a proper table  Yellow  Orange  Red Positive test for reducing. If color remains blue (the color of Benedict’s reagent) Negative result.  Green

9 D.W glucose sucrose starch milk apple juice maltose

B. Lugol’s iodine test for starch  Starch is a polysaccharide consisting of many glucose monomers linked together into long branching chains.  It is the primary storage carbohydrate in plants.  In the presence of iodine (I 2 -KI), a solution containing starch will turn blue-black in color. 10

11 Fill the test tubes with 2 ml of one of the following solutions. D.W glucose sucrose starch milk apple juice Potato juic e

12  A blue-black Add two drops of lugol’s iodine to each test tube. Record the result in the report. If color change to: Positive test for starch If color remains yellow - brown (the color of the iodine) Negative result.

13 D.W glucose sucrose starch milk apple juice Potato juice

 Proteins are the key substances in the structural and physiological function of living things.  Proteins are polymers of amino acids in which the carboxyl group of one amino acid is linked with the amino group of the next amino acid in a covalent bond called the peptide bond. A. Ninhydrin test for amino acids  Ninhydrin reagent reacts with free amino groups i.e free amino acids to form a purple or violet colored substance. 14

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 To each of the test tubes, add 10 drops of ninhydrin reagent and heat the test tubes in boiling water for 5 minutes (avoid inhaling, poisonous fumes).  A purple color is the +ve result.  Record the color of the tubes content in the lab report. 16

B. Biruet test for polypeptides  The test reveals the presence of peptide bond i.e. proteins  Biuret reagent CuSo 4 reacts with the peptide bonds between the amino acids changing in color from light blue to violet under alkaline conditions.  The intensity of the violet color is proportional to the protein concentration.  In the test, Cu +2 must complex with at least four to six peptide bonds to produce a color. Biuret reagent does not react with free amino acids. Short peptides don’t react positively. 17

18 Fill the test tubes with 2 ml of one of the following solutions. D.W Lysine starch albumine milk

19 Fill each test tube with 2 ml of Biuret reagent 19 If color change to: Record your results in a proper table.  Violet Positive test for Biuret test If color remains blue (the color of Biuret reagent). Negative result.

20 D.W milk Lysine starch albumine

 Lipids are a heterogeneous group of compounds that are insoluble in water, but are soluble in organic solvents such as ether and acetone.  There are three major classes of lipids:  Neutral fats (triglycerides).  Phospholipids  Steroids A. Sudan red test for fats  Sudan red is a lipid soluble dye, when added to a mixture of lipids and water, The dye will move into the lipid layer giving the lipid a red color. 21

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23  Add 10 drops of Sudan IV solution to the test tube and mix.  Record your observations.  Two layers are formed, the upper one is the lipid stained with Sudan red IV  The water remains in the bottom layer

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