Quick questions on Enzymes and chemical digestion (SACE Stage 2 Nutrition)

Salivary amylase, made in the mouth, starts breaking starch into the disaccharide maltose. Pancreatic amylase continues this in the small intestine. Other enzymes such as maltase and sucrase then split disaccharides into single sugars (monosaccharides) ready for absorption.

Pepsin works in the stomach, where the acidic environment suits it, breaking proteins into shorter chains. In the small intestine, trypsin and other proteases from the pancreas continue the job, finishing with single amino acids.

Lipase from the pancreas breaks lipids (triglycerides) into fatty acids and glycerol. Lipase needs help: bile from the liver first emulsifies fat into tiny droplets, which gives lipase a much larger surface area to work on. Bile is not an enzyme; it is a physical helper.

As temperature rises, molecules move faster and collide more often, so the reaction speeds up to an optimum around body temperature (37 degrees Celsius). Above this, the protein begins to denature: its shape changes, the active site no longer fits the substrate, and activity falls sharply. Denaturing by heat is permanent.

Each enzyme has an optimum pH. Pepsin works best in the strong acid of the stomach (about pH 2), while pancreatic enzymes such as trypsin and amylase work best in the slightly alkaline small intestine (about pH 8). Moving an enzyme far from its optimum pH also distorts the active site and slows or stops it.

More substrate or more enzyme generally increases the reaction rate until one of them becomes the limiting factor.