Biochemical Tests

Question 1

What is the test for proteins?

Answer 1

• Biuret test.
• Add sodium hydroxide solution to sample, then add copper sulfate solution to sample.
• If solution turns purple then protein is present.

Question 2

What is the test for lipids?

Answer 2

• Emulsion test.
• Add ethanol to sample and then add water and shake.
• If solution turns a milky, white colour then a lipid is present.

Question 3

What is the test for starch?

Answer 3

• Iodine test.
• Add potassium iodide solution which has iodine dissolved in it to the sample.
• If the sample turns from brown to purple/black then starch is present.

Question 4

What is the test for reducing sugars?

Answer 4

• Benedict’s test.
• Add Benedict’s reagent to sample and heat it in a water bath for 5 minutes.
• If the solution turns from blue to a brick red then reducing sugar is present.

Question 5

What is the test for non-reducing sugars?

Answer 5

• Benedict’s test.
• If reducing sugar test is negative, then firstly dilute hydrochloric acid needs to be added to the sample first then add sodium hydrogencarbonate and then carry out the normal Benedict’s test.
• If sample turns from blue to brick red then non-reducing sugar is present.

Question 6

What are reagent test strips?

Answer 6

-They are test strips covered in reagent which test for glucose. They change colour is glucose is present and then the colour change is compared to a chart.

Question 7

How can you determine the concentration of a solution?

Answer 7

• Use a colorimeter, which measures the absorbance.

- So the higher the absorbance the more concentrated a solution is.

Question 8

How do you carry out a serial dilution?

Answer 8

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Question 9

What are biosensors?

Answer 9

• It is a device which uses biological molecules like an enzyme to detect chemicals in a solution.
• The biological molecule produces a chemical signal which is converted to an electrical signal by a transducer. This signal is the processed.

Question 10

How does a glucose biosensor work?

Answer 10

• It is used to determine the concentration of glucose in a solution.
• Uses enzyme glucose oxidase and electrodes.
• Enzyme catalyses oxidation of glucose at electrodes which creates a charge and converts it into an electrical signal.
• Signal is processed and used to work out initial glucose concentration.

Question 11

What does chromatography do?

Answer 11

-Separate solutions and identifies it’s components.

Question 12

What is a mobile phase and what is a stationary phase?

Answer 12

• Mobile=when molecules can move - a liquid solvent is used such as water.
• Stationary=when molecules cannot move - uses chromatography paper or has a thin layer of solid such as silica gel.

Question 13

How do you set up paper chromatography?

Answer 13

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