Biological Molecules Quiz

Which reagent is used to test for reducing sugars?

• Iodine solution

• Biuret reagent

• Benedict’s solution

• Ethanol

A positive Benedict’s test produces which colour when reducing sugars are present in high concentration?

• Blue

• Brick-red

• Black

• Purple

What colour change is seen when iodine solution is added to starch?

• Blue to brick-red

• Yellow to purple

• Brown to blue-black

• Clear to white emulsion

The emulsion test for lipids involves mixing ethanol with the sample and then adding:

• Water

• Iodine

• Benedict’s solution

• Biuret reagent

A positive Biuret test indicates the presence of:

• Reducing sugars

• Lipids

• Proteins

• Starch

Semi-quantitative Benedict’s tests can be standardised by:

• Measuring the exact volume of iodine added

• Timing the colour change or comparing to a colour chart

• Using distilled ethanol as a control

• Heating without boiling

To test for non-reducing sugars such as sucrose, the sample must first be:

• Neutralised with alkali

• Hydrolysed with dilute acid

• Heated without Benedict’s solution

• Dissolved in ethanol

Which of the following correctly describes the ring form of α-glucose?

• OH group on carbon 1 is above the plane

• OH group on carbon 1 is below the plane

• Carbon 2 carries a CH₂OH group

• Carbon 6 forms part of the ring

The term monomer is best defined as:

• A molecule made of many repeating units

• A small molecule that can join others to form a polymer

• A large macromolecule with complex shape

• A polysaccharide formed by hydrolysis

Which of the following is a reducing sugar?

• Sucrose

• Glucose

• Starch

• Cellulose