Biology- biological molecules

Outline the benedicts test for reducing sugars

• Add an equal amount of benedicts reagent to the sample

• Heat in a mixture bath water at 100 degress for 5 minutes

• Positive result: Color change from blue to green to yellow to orange to brick red.

Outline the Benedicts test for non reducing sugars

• Hydrolyse non reducing sugars (sucrose) into their monomers by adding an equal volume of HCL

• Heat in boiling bath water for 5 minutes

• Neutralise the mixture using sodium hydrogen carbonate solution

• Proceed with the Benedits test as usual

How can the Benedicts test be more quantitative?

• Measure the time from immersing solution in water bath till the first colour change is produced

or

• Create standard solutions of known concentrations, and compare colour change to estimate concentration

Outline the Buiret test for proteins

1. Add an equal volume of sodium hydroxide to a sample at room temperture

2. Add a few drops of dilute copper (II) sulfate solution. Swirl to mix.

3. Positive result: Blue to purple

Negative: Solution remains blue

Describe how to test for and measure the presence of starch in a sample

1. Add iodine solution

2. Positive result: colour changes from yellow-brown to blue-black

Describe the emulsion test for fats and oils

• Add ethanol to the sample and shake

• Allow mixture to settle

• Add an equal volume of water

• Record any observations

Describe the positive result of an emulsion test

White, cloudy emulsion forms

Describe monomer

A single subunit that is used to build larger polymers

Define polymer

A large molecule made up of repeating subunits (monomers) joined together by condensation

Describe macromolecule

A large biological molecule

Define monosaccharide and disaccharide

1. A single unit of carbohydrate

2. 2 units of carbohydrate joined by condensation held by a glycosidic bond