Enzyme unit many kinds of substance besides enzymes (for example, vitamins and hormones). Enzyme unit The enzyme unit (symbol U or sometimes EU) is a unit for the amount of a particular enzyme. One U is defined as the amount of the enzyme that produces a certain amount of enzymatic activity, that is, the amount that catalyzes the conversion of 1 micro-mole of substrate per minute. The conditions also have to be specified: one usually takes a temperature of 25°C and the pH value and substrate concentration that yield the maximal substrate conversion rate. The enzyme unit was adopted by the International
Bubble (physics) during intravenous fluid administration, or during surgery. Bubble (physics) A bubble is a globule of one substance in another, usually gas in a liquid. Due to the Marangoni effect, bubbles may remain intact when they reach the surface of the immersive substance. Bubbles are seen in many places in everyday life, for example: Bubbles form, and coalesce, into globular shapes, because those shapes are at a lower energy state. For the physics and chemistry behind it, see nucleation. Bubbles are visible because they have a different refractive index (RI) than the surrounding substance. For example, the RI of air is