Controlling the Cell

Today s biochemists would have to answer this question, like others in which life as a non-chemical and physical force has 

We can begin by examining the factors that regulate a simple enzymic reaction. The reaction 

For each of the three reactions involved, the set of variables we have described will control the reaction rate. But, over the entire reaction sequence, an additional variable will now operate that did not exist when only one reaction was being discussed, and that is 

Thus the production of Z exerts a controlling influence on W-ase, and, reciprocally, the rate of W-ase controls the production of Z. This type of control is called feedback. It is identical in type to the principle of a thermostat on an electric heater, or the governor of James Watt s steam engine nearly 200 years ago. We can represent a reaction sequence with feedback like this 

Feedback can be of two types. In the type we have considered, Z production inhibited W-ase - this is negative feedback. But if Z production lowered the pH so that W-ase was accelerated and Z production increased, this would be positive feedback. In all feedback reactions, the principle is the same - the rate of a reaction is controlled by a substance which is an ultimate product but not itself directly involved in the reaction. 

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The nucleic acids, deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), are the chemical carriers of a cell s genetic information. Coded in a cell s DNA is the information that determines the nature of the cell, controls the cell s growth and division, and directs biosynthesis of the enzymes and other proteins required for cellular functions. 

Example 4.8A We now revisit the fermentor example 4.8 (p. 4-11). Our question is whether we can control the cell mass and glucose concentration by adjusting only D. 

ADCA is activated by zinc oxide, zinc stearate (strongly) and urea (slowly). Barium stearate, calcium stearate and triethanolamine, when added at 10 phr, moderately activate gas evolution from ADCA. They do not have very much effect on decomposition rate when the cure temperature is at 170 °C, but a marked effect above 180 °C. The rate of decomposition of ADCA is significantly influenced by the particle size of the additive. Effective dispersion and heat transfer through the particle can be a means of controlling the cell quality and the manufacturing method for the product. The correct particle size is selected to achieve the optimum balance between cure and cell development. 

Hung DT, Jamison TE, Schrieber SL. (1996) Understanding and controlling the cell cycle with natural products. Chem Biol 3 623-639. 

Progress in the Development of Agents to Control the Cell Cycle... 

Abstract Inhibitors of the kinases controlling the cell cycle have emerged as an important therapeutic modality for the treatment of cancer. Drug discovery efforts have focused on inhibitors of the cyclin-dependent kinases, the Aurora kinases, and Polo-like kinases. Agents for each kinase are now advancing in human clinical trials. In this review we will summarize the work in this area with special emphasis on the structural biology and structure-activity relationships developed for the many chemotypes explored. 

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