molecules

Three main categories of molecules in living organisms

Carbohydrates, proteins, and lipids.

Elements contained in carbohydrates

Carbon, hydrogen, and oxygen.

Composition of carbohydrates

Sugar molecules joined together in long chains.

Single sugar molecule

Monosaccharide.

Disaccharide

Two sugar molecules bonded together.

Example of a disaccharide

Sucrose (glucose and fructose bonded together).

Polysaccharide

Several sugars joined together in one long chain.

Examples of polysaccharides

Cellulose, starch, and glycogen.

Storage molecules of starch and glycogen

They are insoluble and don't cause water to move into and out of the cell.

Bond in carbohydrates

Glycosidic bonds.

Carbohydrate-rich food sources

Bread, potatoes, pasta.

Test for starch

Add iodine solution. Positive result is a blue/black colour.

Test for sugars

Heat with Benedict's solution. Positive result = brick red, orange, yellow or green.

Elements contained in proteins

Carbon, hydrogen, oxygen, and nitrogen.

Composition of proteins

Long chains of amino acids joined together by peptide bonds.

Dipeptide

Two amino acids joined together.

Polypeptide

Long chains of amino acids.

Bond in proteins

Peptide bonds.

Important cell components made up of proteins

Enzymes, hormones, and antibodies.

Protein-rich food sources

Meat, fish, and beans.

Test for protein

Add Biuret solution. Positive result = purple colour.

Elements contained in lipids

Carbon, hydrogen, and oxygen.

Composition of lipids (triglycerides)

One glycerol and three fatty acids.

Bond in lipids

Ester bonds.

Foods with high lipid content

Butter, oils, nuts, and avocado.

Test for lipids

Dissolve in ethanol, then add water. Positive result = milky white emulsion.

Preparation of a food sample for testing

Crush with mortar and pestle. Dissolve in water. Filter.