Biological Molecules: Answers

What are the individual subunits of:

• carbohydrates

• proteins

• lipids

Biological molecules are long chains (polymers) of repeating smaller units (monomers) joined together in one long chain. The individual subunits, or monomers, within carbohydrates are sugar molecules, proteins are made up of amino acids whereas lipids such as triglycerides are made up of a glycerol molecule and three fatty acids.

What is meant by the term polysaccharide? Give examples of some polysaccharides found in animals and plants.

Polysaccharide means lots of sugar molecules joined together, so the term ‘polysaccharide’ describes a carbohydrate. Some examples are cellulose which is found in plant cell walls, starch which is found in the cytoplasm of plant cells and glycogen which is found in the cytoplasm of animal cells.

What elements are found in proteins?

The elements which bond together to form an amino acid are: carbon, hydrogen, nitrogen and oxygen. Lots of amino acids bonded together forms a protein.

Describe the test you would carry out if you want to detect the presence of lipid in a sample.

The emulsion test is used to detect the presence of lipid. To do the test you add ethanol to the sample along with an equal volume of water. If lipid is present a milky white emulsion should form.

Give the name of the test for protein.

Biuret test.