Final answer:
Saliva contains the enzyme salivary amylase, which starts the chemical digestion of carbohydrates, not proteins. The enzyme lipase is also present but is responsible for the breakdown of fats, not proteins.
Step-by-step explanation:
Salivary amylase is the enzyme present in saliva that begins the digestion process in the mouth by breaking down starches into sugars, such as maltose. This amylase enzyme is specifically designed to target carbohydrates, not proteins. The notion that saliva contains enzymes like lipase is correct, but lipase predominantly catalyzes the hydrolysis of fats. A common practical example illustrating the action of salivary amylase is the sweetness one might taste when chewing a soda cracker for an extended time; this is due to the conversion of starch in the cracker into sugar.
Saliva consists mostly of water but also contains a mixture of substances that aid in digestion and oral health. These include bicarbonate and phosphate ions, which buffer the saliva to maintain a neutral pH, and mucous, which helps in the formation of a food bolus for easier swallowing. Additionally, saliva has antimicrobial properties due to the presence of immunoglobulin A and lysozyme.