A group of students was given samples of four different foods to test. The samples were prepared by dissolving powdered food in distilled water. The four foods were identified as W, X, Y, and Z. They were also given a sample of distilled water.
They carried out three tests on the five samples. Test 1 was for glucose, test 2 was for protein and test 3 was for starch. The results of the tests are shown in the table.

Now , select the correct options regarding it .

Options

A. Samples W and Z are rich in proteins while samples X and Y are rich in starch.
B. Samples W, X and Z contain starch while samples W and Z contain protein also.
C. Sample Z contains both protein and glucose but not starch.
D. Sample X and Z contain glucose only and sample Y contains starch only.

Answer

C

Explanation

To test a food sample for starch, its fine paste is made and 2-3 drops of iodine solution is added to it. If the paste turns blue-black, the tested food sample contains starch
To test a food sample for protein, the food is mashed into a thin paste and 2 drops of copper sulphate solution and 10 drops of caustic soda (sodium hydroxide solution) are added to it. If the solution becomes purple, the given food sample contains protein whereas if solution remains blue the food does not contain protein.
To test the presence of glucose in food item, Benedict.s reagent is added to its paste and, the solution is boiled. The solution will turn red if high concentration of glucose is present whereas it will turn yellow, if low concentration of glucose is present. Hence, according to the given table sample W contains proteins but not glucose and starch, sample X contains glucose but not protein and starch, sample y contains starch but not glucose and protein whereas sample Z contains both proteins and glucose but not starch.