Biological origin catalyst

Enzymes may be described a organic catalysts of biological origin. The majority are obtained from the interior of cells, but some are obtained from natural secretions such as the digestive juices and milk. For a full discussion of the nature of enzymes and the mechanism of their reactions the student should consult a work such as Chemistry and Methods of Enzymes, by J. B. Sumner and G. F. Somers (Academic Press, New York), or Enzymes, by M. Dixon and E. C. Webb[(Longman Group Ltd.). The following points should however be noted ... 

Macromolecules of biological origin perform various functions in the body. For example, proteins which perform the role of biological catalysts in the body are called enzymes, those which are crucial to communication system in the body are called receptors. Carrier proteins carry polar molecules across the cell membrane. Nucleic acids have coded genetic information for the cell. Lipids and carbohydrates are structural parts of the cell membrane. We shall explain the drug-target interaction with the examples of enzymes and receptors. 

Enzymes are biological catalysts—i. e substances of biological origin that accelerate chemical reactions (see p. 24). The orderly course of metabolic processes is only possible because each cell is equipped with its own genetically determined set of enzymes. It is only this that allows coordinated sequences of reactions (metabolic pathways see p. 112). Enzymes are also involved in many regulatory mechanisms that allow the metabolism to adapt to changing conditions (see p.ll4). Almost all enzymes are proteins. However, there are also catalytically active ribonucleic acids, the ribozymes" (see pp. 246, 252). 

Abiotic supramolecular systems can be used as models for biological catalysis and as catalysts for other reactions that are not of biological origin. 

This Part will be focused on the fundamentals and applications of membrane-assisted transformation processes, i.e. membrane reactors. Two separate chapters are dedicated to the fundamentals of membrane reactors using traditional chemical catalysts at high temperature (>200 °C) and catalysts of biological origin or biomi-metic at low temperature (<100 °C). 

Enzymes are catalysts. Nature has designed them to perform specific tasks necessary for the survival of the organism producing the enzyme. The organic chemist tends to name enzymes biocatalysts which means nothing more than catalysts of biological origin. 

MBRs are combined processes in which a biochemical conversion (by the action of a catalyst of biological origin, i.e., an enzyme) and a physical separation process are simultaneously carried out. 

When PHB is crystallized from the melt it forms large banded spherulites. Because of its biological origin and the extensive purification process used to separate it from cell debris, the polymer does not contain inorganic catalyst residues or other impurities which could act as heterogeneous nucleation centres. As a result it is very easy to obtain samples of PHB with low nucleation density that form massive spherulites on cooling from the melt. With a modicum of care, spherulites of several millimetres diameter that are visible to the naked... 

The accomplishments of this group were responsible for changing the study of enzymes from an obscure art concerned with biological mysteries to a branch of science investigating chemical and physical properties of catalysts of biologic origin. 

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