Biochemical tests

Question 1

what does the benedict’s test for?

Answer 1

reducing and non-reducing sugars

Question 2

how does the benedict’s test work for reducing sugars

Answer 2

1- place the sample to be tested in a boiling tube and add an equal volume of benedicts reagent
2- heat the mixture gently in a water bath

If reducing sugars are present, they will react with the copper ions in the reagent, reducing them from blue ions to red ions. this forms a brick red precipitate

Question 3

how does benedicts test work for non-reducing sugars

Answer 3

if the non-reducing sugar is first boiled with hydrochloric acid, it will then give a positive result when warmed with benedicts solution, forming a brick red precipitate

Question 4

what does the iodine test for?

Answer 4

starch

Question 5

how does the iodine test for starch work?

Answer 5

iodine dissolved in potassium iodide solution are mixed with a sample
if the solution changes from yellow/brown to blue/black then starch is present

Question 6

what is a colorimeter

Answer 6

it is a piece of equipment used to quantitatively measure the absorbance or transmission of light through a coloured solution.
the more concentrated a solution the more light it will absorb and the less light it will transmit.

Question 7

what are biosensors

Answer 7

biosensors use biological components to determine the presence and concentration of molecules such as glucose.
consists of :
- molecular recogniton
- transduction
- display

Question 8

what does the emulsion test for?

Answer 8

lipids

Question 9

how does the emulsion test

Answer 9

1- sample is mixed with ethanol
2-resulting mixture is mixed with water and shaken

if a white emulsion forms as a layer on top of the solution this indicates the presence of a lipid.

Question 10

what does the biuret test for

Answer 10

proteins

Question 11

how does the biuret test work

Answer 11

1- add sodium hydroxide to the sample
2- add a few drops of copper sulfate solution to the sample

if a colour change from blue to lilac takes place then protein is present

Question 11

what is chromatography

Answer 11

it is a technique that can be used to separate a mixture into its individual components
it relies on differences in the solubility of the components

Question 12

what are two phases in chromatography

Answer 12

mobile phase and stationary phase