2.1.2: Biuret, Ethanol, And Colorimeter

Question 1

What color does iodine turn in the presence of starch?

Answer 1

Blue/black

Iodine is orange/brown when no starch is present.

Question 2

What is the purpose of the Biuret test?

Answer 2

To test for the presence of proteins

A blue solution turns purple if a protein is present.

Question 3

What are the steps in the Ethanol Emulsion Test for lipids?

Answer 3

1. Add ethanol and shake to dissolve the sample
2. Add distilled water
3. A white emulsion forms in the presence of a lipid

This test confirms the presence of lipids.

Question 4

What is the use of a colorimeter in biochemical tests?

Answer 4

To obtain quantitative results for concentration

It measures the percentage transmission of light.

Question 5

What is the first step in using a colorimeter?

Answer 5

Set the filter in the colorimeter

Calibration is done using distilled water.

Question 6

What is a calibration curve?

Answer 6

A graph created using results from known concentrations

It is used to determine unknown sample concentrations.

Question 7

Define a biosensor.

Answer 7

A device that quantifies the concentration of a sample

It uses immobilised DNA or protein to detect samples.

Question 8

What happens when an analyte binds to immobilised DNA/protein in a biosensor?

Answer 8

It causes a change in a transducer that releases an electronic current

This current is processed to determine concentration.

Question 9

Fill in the blank: The emulsion test is used to check for the presence of _______.

Answer 9

Lipids

Question 10

True or False: The Biuret solution turns purple in the absence of proteins.

Answer 10

False

The solution remains blue if no proteins are present.