A species of bacteria can synthesize the amino acid histidine, so they do not require histidine in their growth medium. A key enzyme, which we will call histidine synthetase, is necessary for histidine biosynthesis. When these bacteria are given histidine in their growth medium, they stop synthesizing histidine intracellularly. Based on this observation alone, propose three different regulatory mechanisms to explain why histidine biosynthesis ceases when histidine is in the growth medium. To explore this phenomenon further, you measure the amount of intracellular histidine synthetase protein when cells are grown in the presence and absence of histidine. In both conditions, the amount of this protein is identical. Which mechanism of regulation is consistent with this observation?

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Modes of Nutrition

It is a biological process of providing or obtaining food that is necessary for growth and health. It includes many physiological processes - absorption, ingestion, assimilation, catabolism, excretion, etc. In biology, the science that deals with nutrition's physiological and chemical processes are called "nutritional science."