2.2 Test for biological Molecules

Question 1

steps to reducing sugar test

Answer 1

1) Add benedict’s solution to sample
2) Stir it & place in a water bath at 80 degrees for 3 minutes
3) Note colour change

Question 2

why is there a colour change when testing for reducing sugars

Answer 2

• Reducing sugars gives electrons
• Reducing sugars give electrons to the Cu2+ ions, turning them into Cu which forms orange/red colour

Question 3

How to carry out carbohydrate test

Answer 3

1) take iodine and add a few drops to the sample
2) If turns black starch is present

Question 4

why does iodine cause colour change in starch

Answer 4

• The iodine ions forms a triiodide
• It then slips into helix of amylose and causes colour change

Question 5

what is the steps for testing for non-reducing sugars

Answer 5

• First test for RS
• Take a separate sample & boil it with HCL to hydrolyse sucrose into glucose + fructose
• Cool Solution
• Add Soduim Hydrogen Carbonate to neutralise it
• Test for RS

Question 6

How to carry out test for lipids

Answer 6

• Take a sample & mix throughly with ethanol & shake
• Filter & add water
• Cloudy precipitate indicates presence of lipids

Question 7

How to carry out test for Proteins

Answer 7

• Add buiret solution
• Forms liliac colour

Question 8

why does colour change in protein test

Answer 8

The colour change is formed due to a complex being formed by the Nitrogen atom in peptide chain and the Cu2+

Question 9

calorimetry

Answer 9

Piece of equipment used to quantitatively measure absorbance or transmission of light by a colored solution.

Question 10

6 steps to calorimetry

Answer 10

Filter is placed in colorimeter.

Calorimeter is then calibrated using distilled water.

Benedict’s test is performed on a wide range of known concentrations of glucose.

Solutions are filtered to remove precipitate

% transmission of each solution is measured.

The calibration curve is then plotted.

Question 11

what is a biosensor

Answer 11

Using biological components to determine the presence and concentration of molecules such as glucose.

Question 12

3 steps to biosensor

Answer 12

1) Molecular recognition: Single strand of DNA or protein which are complementary to test sample is immobilised. When sample is added, it will bind to DNA/protein

2) Transduction: This binding causes change in a transducer, resulting in an electronic current.

3) Display: This current is processed to determine the concentration of sample present.

Question 13

what is Thin Layer Chromotography

Answer 13

Technique used to seperate the individual components of mixture

Question 14

what is the stationary phase

Answer 14

Silicia gel is applied to chromotography paper & then amino acids are then added to one end

Question 15

what is the mobile phase

Answer 15

organic solvent moves up chromotography paper resulting in amino acids moving different distances

Question 16

7 steps to chromotography

Answer 16

Wearing gloves draw a 2cm line from bottom edge.

Mark 4 equally spaced points along the pencil line.

Amino acids are placed on the four dots.

Placed in a jar with a solvent that’s no deeper than 1cm, & the jar is then closed

The plate is left until the solvent has reached 2cm from the top & left to dry

Spray with ninhydrin, which reacts with amino acids to form a purple slash brown color.

Mark each spot with pencil and measure distance