growth assay

In biology, a growth assay is a method used to measure the biological activity of substances, particularly vitamins. This is often done by observing the growth of organisms, such as microorganisms or animals, in response to varying amounts of the substance being tested.12

For example, in a growth assay for vitamins, animals like rats or chicks are fed different quantities of a vitamin. Their increase in body weight is then measured to determine the vitamin's effectiveness. Similarly, microorganisms can be used, where their growth rate in a medium with a vitamin is compared to their growth with a known amount of the pure vitamin. This helps determine the amount of biologically active vitamins present in a sample.21

A classic biological growth curve, often seen in bacterial colonies, typically includes four phases: lag, logarithmic (exponential), stationary, and death.3