Final answer:
Amylase is an enzyme in saliva that starts the digestion of starch by decreasing the energy necessary for the reaction. It breaks down starch into maltose and glucose, facilitating the absorption of these simple sugars by the body.
Step-by-step explanation:
Amylase is a vital enzyme found in saliva that kickstarts the digestion of starches in the mouth. The action of amylase on starches triggers a reaction in which the starch molecules are broken down into smaller sugars, like maltose and ultimately glucose. The best description of how amylase starts this reaction is that it decreases the energy needed to start the reaction (Option C).
The presence of amylase in saliva allows for the chemical digestion of carbohydrates, such as amylose and glycogen, to begin as soon as the food enters the mouth. Amylase acts by attacking the α-glycosidic linkages in the starch molecules, resulting in a mixture of shorter polysaccharides, dextrins, and disaccharides, like maltose, and eventually individual glucose units which can be absorbed by the body. It does not bind directly with glucose to start this reaction, nor does it provide extra energy, nor does it change the shape of the starch; it rather facilitates the reaction by lowering the activation energy required.