Biological Molecules: Biochemical Tests

Question 1

What is the BIURET TEST?

Answer 1

-A simple BIOCHEMICAL REACTION to detect the PRESENCE OF PROTEIN
-If the BIURETS SOLUTION turn PURPLE, then PROTEIN is PRESENT

Question 2

Describe how you would carry out the BIURET TEST for PROTIENS

Answer 2

-Add BIURETS REAGENT to SAMPLE SOLUTION
-If it goes from BLUE->LILAC, a PROTEIN is PRESENT

Question 3

What is the BENEDICTS TEST?

Answer 3

-A simple BIOCHEMICAL REACTION to detect the presence of REDUCING SUGARS
-If SOLUTION goes from BLUE->BRICK RED, a REDUCING SUGAR is PRESENT

Question 4

Describe how you would carry out a BENEDICTS TEST for REDUCING SUGARS

Answer 4

-Add appropriate amount of BENEDICTS REAGENT to SAMPLE SOLUTION
-Heat in WATER BATH for 10 MINUTES at 60oC
-If SOLUTION changes colour from BLUE->BRICK RED, a REDUCING SUGAR IS PRESENT

Question 5

What is the IODINE STARCH TEST?

Answer 5

-A simple BIOCHEMICAL REACTION to detect the presence of STARCH
-If the SOLUTION changes to a BLUE-BLACK COLOUR, there is STARCH PRESENT

Question 6

Describe how you would carry out the IODINE STARCH TEST

Answer 6

-Add SAMPLE SOLUTION to a SPOTTING TRAY
-Add POTASSIUM IODIDE to the SAMPLE SOLUTION
-If the colour changes to a BLUE-BLACK, STARCH is PRESENT

Question 7

Describe how you would test for a NON-REDUCING SUGAR

Answer 7

-Add DILUTE HCL to the SAMPLE, HEAT in water that is bought to a BOIL
-NEUTRALISE SOLUTION with NAHCO3
-Carry out BENEDICTS TEST as normal
-If the colour changes to an ORANGE-RED (or precipitate), a NON-REDUCING SUGAR is PRESENT

Question 8

Describe how you would carry out an EMULSION TEST for LIPIDS

Answer 8

-Dissolve SAMPLE SOLUTION in ETHANOL
-Add WATER and mix
-If a CLOUDY WHITE PRECIPITATE FORMS, a LIPID is PRESENT

Question 9

Describe how you could carry out the SUDAN III TEST for LIPIDS

Answer 9

-Add EQUAL amounts of FOOD & WATER to a TEST TUBE
-Then add 3 drops of SUDAN III and SHAKE
-If a RED-STAINED LAYER FORMS, a LIPID is PRESENT