Biology & Chemistry Sim · Enzymes
Choose an enzyme, slide the pH, and watch the reaction speed up near its optimum — and stall when the enzyme denatures.
Bubble speed = reaction rate. The curve shows activity across the whole pH range; the marker is your current pH.
Pepsin digests protein in your stomach. Amylase works in your mouth. Trypsin works in the small intestine. Catalase protects your cells.
An enzyme's active site is held in shape by ionic bonds and hydrogen bonds. At the optimum pH that shape fits its substrate perfectly. Move the pH and the charges on amino acids change, warping the active site — so the reaction slows.
Far enough from the optimum, the enzyme's shape unravels — it is denatured, and for many enzymes this change cannot be undone. Pepsin is built for stomach acid (optimum around pH 2) and slowly loses its shape in neutral conditions, while salivary amylase (optimum ~pH 7) keeps working for a while after swallowing and only denatures as the stomach's acid takes over.
Your digestive tract is a pH assembly line: mouth ~7, stomach ~2, small intestine ~8. Each enzyme evolved for its own zone, which is why digestion happens in stages instead of all at once.