Chapter 14.2, Problem 3CC

Summary Introduction

To explain: The “decision-making” process used by an E. coli cell growing in a medium containing arabinose, no glucose, and lacking tryptophan.

Introduction: Various regulatory “decisions” are made by microbial cells depending on the presence or absence of substrate or product. If the substrate of the pathway is present in the environment and a preferred carbon and energy source is not, then microbial cells synthesize the enzymes of a specific catabolic pathway. Conversely, the synthesis of enzymes is inhibited, when the end product of the pathway is present.