Practice Questions

Lipids are defined by their hydrophobic nature, being soluble in non-polar organic solvents (like ether, chloroform) but insoluble in water. This contrasts with carbohydrates and proteins which are generally hydrophilic.

The formation of a disaccharide involves the removal of a water molecule (dehydration synthesis) to form a glycosidic linkage between two monosaccharides. A peptide bond links amino acids, and an ester bond links fatty acids to glycerol.

Glucose and fructose both have the molecular formula C6H12O6. Glucose is an aldehyde sugar (aldose), while fructose is a ketone sugar (ketose). This difference in the carbonyl functional group makes them structural isomers, not identical molecules.

The term "carbohydrate" literally means hydrated carbon, reflecting the general ratio of one carbon to two hydrogens to one oxygen atom. Proteins contain nitrogen, and nucleic acids contain phosphorus, distinguishing them from this basic formula.

Carbohydrates, particularly monosaccharides like glucose, are the primary and immediate energy source broken down during cellular respiration. Proteins are mainly structural and catalytic, lipids are for long-term energy storage, and nucleic acids store genetic information.