The yeast "Saccharomyces cerevisiae" has been used by human beings since ancient times for its ability to convert sugar to alcohol. Continual exposure to glucose in the natural environment for innumerable generations has probably enabled "S. cerevisiae" to grow in fermentative mode on sugars by switching off the genes responsible for respiration even under aerobic conditions. This phenomenon is referred to as the Crabtree effect. The present review focuses on glucose repression in "S. cerevisiae" from a physiological perspective. Physiological studies presented involve batch and chemostat experiments of the wild type and a mutant that lacks a trait partially responsible for the fermentative behavior. Various undergraduate student exercises have been (and can be) formulated to illustrate the concept of glucose repression.