Enzymes as biological catalysts

Enzymes have no effect on the AG or of a reaction. They simply speed up the rate at which a reaction approaches equilibrium. For example, in the. reaction S = 

In the presence of an appropriate enzyme, both ki and are enhanced to the same degree. Thus, if At increases 10 -fqld, A-i must also increase 10 -fold. AG and are unchanged (Fig. 4-16). 

Enzymes do more than accelerate reactions. They also couple reactions in a productive manner. For example, consider the two reactions below  

The cleavage of A-B can supply sufficient energy to drive the synthesis of C-D. Yet, if reactions 1 and 2 occurred in different parts of the cell at different times there would be no way of using the energy of reaction 1 to push reaction 2, even if both occurred at a rapid fate. In a living cell, the overall process might be coupled in a productive manner as. follows  

In reaction 3, A-B is cleaved by enzyme E, and a portion of the energy made available is used to condense B with X to yield an activated form of B. The energy conserved in B X is retained when X is transferred to Y in a reaction 

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The activity of redox enzymes as biological catalysts depends, in some cases, on their protein structure. In other situations the presence of non-proteic cofactors is necessary the cofactors can be metals in the case of metalloenzymes, or organic molecules in the case of coenzymes (Table 17.3). 

Recently, the use of enzymes as biological catalysts in the synthesis of polyanilines has attracted great interest due to their environmental... 

Enzymes are proteins that act as biological catalysts. They not only bind molecules, but also provide a special environment in which the molecules are chemically modified. Enzymes cannot promote a reaction that is not energetically favourable, but by binding the reagents in the necessary orientation and in close proximity, they signi-... 

Enzymes constitute a large superfamily of proteins acting as biological catalysts capable of accelerating over a million-fold the rate of chemical reactions within cells. ° On the basis of the type of reaction catalyzed, enzymes are organized using a classification scheme that has prevailed for decades." ... 

Mueller RJ (2006) Biological degradation of synthetic polyesters - enzymes as potential catalysts for polyester recycling. Process Biochem 41 2124-2128... 

Enzymes are large proteins that function as biological catalysts and whose specificity is due to a lock-and-key fit between enzyme and substrate. Enzymes contain a crevice, inside which is an active site, a small three-dimensional region of the enzyme with the specific shape necessary to bind the proper substrate. 

Enzymes are proteins that act as biological catalysts. They facilitate chemical modification of substrate molecules by virtue of their specific binding properties, which arise from particular combinations of functional groups in the constituent amino acids at the so-called active site. In many cases, an essential cofactor, e.g. NAD+, PLP, or TPP, may also be bound to participate in the transformation. The involvement of enzymes in biochemical reactions has been a major theme throughout this book. The ability of enzymes to carry out quite complex chemical reactions, rapidly, at room temperature, and under essentially neutral conditions is viewed with envy by synthetic chemists, who are making rapid progress in harnessing this ability for their own uses. Several enzymes are currently of importance commercially, or for medical use, and... 

Enzymes are specialized proteins that act as biological catalysts. They can accelerate chemical reactions without being changed themselves. Most enzymatic reactions occur within a narrow temperature range, from 30 to 40°C. Each enzyme usually only reacts with only a small number of closely related compounds. Some require the presence of additional small non-protein molecules (coenzymes). 

Enzymes serve as biological catalysts. They speed up reactions without changing the energies of the reactants (called substrates) and products. Without enzymes, most of the reactions in our cells would not go fast enough to keep us alive. 

Enzymes are biological catalysts, all of which are proteins, except for a class of RNA-modifying catalysts known as ribozymes ribozymes are molecules of ribonucleic acid that catalyse reactions on the phosphodiester bond of other RNAs. The International Union of Biochemistry and Molecular Biology have developed a nomenclature for enzymes, the EC numbers each enzyme is described by a sequence of one of four numbers preceded by EC . The first number broadly classifies the enzyme based on its mechanism. 

As we have seen, the breakdown or detoxication (metabolism) of a chemical is carried out by enzymes. These biological catalysts are proteins that are produced with information encoded in DNA. If there is an error (known as a mutation) in the DNA code that holds the information, the enzyme (protein) that is produced may be faulty. Mutations occur naturally and are passed on from one generation to the next. Some are benign, others potentially lethal. An example of this is the mutation that causes the disease haemophilia, which was carried by Queen Victoria and which afflicted various male members of the royal families of Europe who were descended from her. 

Homogeneons catalysts are present in the same phase as the reaction being catalyzed whereas heterogeneous catalysts are present in a different phase. Enzymes are biological catalysts that bind substrates with exquisite selectivity, position reactants at optimal locations and stabilize transition states, all of which leads to lower activation barriers than those in the uncatalyzed reaction. 

Enzymes are large proteins that function as biological catalysts. 

Functioning as biological catalysts, enzymes specifically accelerate a huge number of chemical reactions at room temperature and normal pressure. The application of enzymes in analytical chemistry is not a new concept. As long as 55 years ago phosphatases were used as analytical tools. The importance of enzymes as analytical reagents in clinical chemistry, food analysis and the pharmaceutical industry has been steadily increasing since that time. At present, enzymes are being routinely employed for the determination of about 80 different substances. 

Entropy. A direct measure of the randomness or disorder of a system. (18.1) Enzyme. A biological catalyst. (13.6) Equilibrium. A state in which there are no observable changes as time goes by. (14.1)... 

We have seen that hydration of a double bond requires a trace of acid as a catalyst In the cell, this reaction is catalyzed by an enzyme, or biological catalyst, called fumarase. 

Enzymes are proteins that serve as biological catalysts. They speed up biochemical reactions so that life processes can function. These enzymes are called a(l 4) glycosidases because they cleave a(l 4) glycosidic bonds. 

Proteins serve as biological catalysts (enzymes) and protective antibodies. Transport proteins carry materials throughout the body. Protein hormones regulate conditions in the body. Proteins also provide mechanical support and are needed for movement. 

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