biochemical tests

Question 1

describe the methods used to test for lipids

Answer 1

great test substance
mix with ethanol
add ice cold water
shake mixture

Question 2

describe the positive and negative results of the test for lipids

Answer 2

positive: milky white emulsions
negative: remains clear

Question 3

describe the method used to test for proteins

Answer 3

mix test substance with biuret reagent

Question 4

what is biuret reagent made of

Answer 4

sodium hydroxide and copper sulfate solutions

Question 5

describe the positive and negative results of the test for proteins

Answer 5

positive: turns lilac
negative: stays blue

Question 6

describe the method used to test for starch

Answer 6

mixed test substance with iodine

Question 7

describe the positive and negative results of the test for starch

Answer 7

positive: turns blue/black
negative: stays yellow/orange

Question 8

describe the method used to test for reducing sugars

Answer 8

add Benedict’s solution to test substance and heat in a water bath

Question 9

describe the positive and negative results of the test for reducing sugars

Answer 9

positive: brick-red precipitate forms
negative: stays blue

Question 10

which carbohydrates will the reducing sugars test work for

Answer 10

all monosaccharides and disaccharides expect sucrose

Question 11

describe the method used to test for non-reducing sugars

Answer 11

perform reducing sugars test with Benedict’s solution, if it remains blue, boil with hydrochloric acid (to hydrolyse the glucosidic bonds), cool and neutralise with sodium carbonate, repeat Benedict’s test

Question 12

describe the positive and negative results for the test for non-reducing sugars

Answer 12

positive: brick-red precipitate form
negative: stays blue