Enzymes Are Catalysts

A. Enzymes are catalysts that increase the rate or velocity, v, of many physiologic... 

Enzymes are catalysts that accelerate metabolic processes in organisms. The word enzyme comes originally from the Greek term enzymos for leavening. Enzymes are... 

Enzymes are catalysts, and catalysts have two key qualities. First, catalysts increase the rate of a reaction. Second, catalysts are not consumed in the reaction and therefore do not appear in the overall balanced reaction equation. Catalysts appear throughout everyday life. Most simple hand tools are catalysts. For example, a shovel greatly accelerates the rate at which one can move dirt or gravel. Furthermore, the same shovel can be used day after day and work as efficiently on the last day as on the first. A shovel facilitates a process but is not consumed by the process. Moving dirt does not absolutely require a shovel, but using a shovel certainly beats using one s bare hands. 

Enzymes are catalysts, substances that play a role in specific chemical reactions, but which are not changed by the reaction. Thus, as a result of the enzyme-substrate reaction, the enzyme stays the same but the substrate is changed. Its shape can be different, or it can be broken down into products or combined with another molecule to make something new. 

Enzymes are catalysts that change the rate of a reaction without being changed themselves. Enzymes are highly specific and their activity can be regulated. Virtually all enzymes are proteins, although some catalytically active RNAs have been identified. 

Enzymes as catalysts Enzymes are catalysts that increase the rate of a chemical reaction without being changed themselves in the process. In the absence of an enzyme, the reaction may hardly proceed at all, whereas in its presence the rate can be increased up to 107-fold. Enzyme catalyzed reactions usually take place under relatively mild conditions (temperatures well below 100°C, atmospheric pressure and neutral pH) as compared to the corresponding chemical reactions. Enzymes are also highly specific with respect to the substrates that they act on and the products that they form. In addition, enzyme activity can be regulated, varying in response to the concentration of substrates or other molecules (see Topic C5). Nearly all enzymes are proteins, although a few catalytically active RNA molecules have been identified. 

Linus Pauling pointed out many years ago (5) that enzymes are catalysts because they can bind strongly the transition states of chemical reactions. Typical accelerations by cyclodextrin or its derivatives are in the range between 10- and 300-fold this very modest accelera-... 

Enzymes as green catalysts Enzymes are catalysts that occur in all living organisms. They control a wide variety of chemical processes necessary for the maintenance, growth, and reproduction of cells. It has long been known that the role of enzymes in life processes is to modify naturally occurring compounds. More recently... 

Because enzymes are catalysts (and not substrates), enzyme rate equations are usually of the shape ... 

Enzymes are catalysts, i.e. they will not get worn out. It is therefore possible to operate with very low amounts of the enzyme. All these facts point to a very cost-effective possibility for the manufacturing of flavour extracts. 

Enzymes are catalysts that speed up or slow down reactions for your cells. 

Enzymes are catalysts made by living cells. They help speed up chemical reactions In the human body Each enzyme will work in only one type of reaction. Enzymes help digest food in the body. They help do this in only a few hours. Digestion would take several weeks without enzymes. 

Enzymes are catalysts that function by lowering the value of AG (Figure 1C) rather than by raising the free energy of the starting materials. However, any mechanism that decreases AG will increase the rate of the reaction. The mechanisms which enzymes use to lower AG are numerous and are not all thoroughly understood. However, some of the known mechanisms are responsible for some of the features most characteristic of biological systems. 

All enzymes are catalysts which act to increase reaction rates. In fact, in most cases, the difference between enzyme catalyzed and noncatalyzed reactions is so great that only the enzyme-catalyzed reactions occur to any significant extent in vivo. Exactly how enzymes participate in this process has been detailed earlier in this book and will not be reviewed here. However, in order to understand enzyme adaptation, it is essential that a few basics of enzyme kinetics be reviewed. The basic enzyme mechanism describes the case where a single substrate binds to an enzyme before being chemically converted to a product. Although the majority of enzyme-catalyzed reactions are two-substrate reactions, several can be adequately described by this mechanism and an understanding of this mechanism is essential... 

Enzymes are catalysts. Catalysts modify the rate of a reaction because they provide an alternative reaction pathway that requires less energy than the uncatalyzed reaction. Most enzymes are proteins. 

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. 

In heterogeneous catalysis, which is of great industrial importance, the catalyst is a solid and the reactants are gases or liquids. In homogeneous catalysis, the catalyst and the reactants are in the same phase. Enzymes are catalysts in living systems. 

Enzymes are catalysts that are found in living systems. They are globular proteins that is, they are polymers of amino acids folded to form a compact, roughly spherical shape. Within the enzyme are cavities containing active sites to which a substrate attaches and then undergoes chemical change. 

At the outset, one distinction to recognize between the classes of biological recognition compounds is that enzymes are catalysts of reactions, and thus sensors that utilize the catalytic capability of enzymes will consume the analyte. 

Enzymes are catalysts. They do not affect the equilibrium of a chemical reaction, but they do affect the rate at which the equilibrium is approached. Enzymes are usually quite specific in the reaction(s) they catalyze. 

Enzymes are, first and foremost, catalysts. More specifically, enzymes are catalysts made by cells for chemical reactions which occur in biochemical processes. Structurally, enzymes are complex and highly specialized proteins, which are... 

The above reactions have been described in terms of substrate oxidation which is the predominant metabolic pathway. However, as enzymes are catalysts the reaction in the reverse direction - reduction of substrate by dihydroflavin - will occur by the microscopically reversed mechanisms. 

Equilibrium Manipulation - Enzymes are catalysts and therefore serve only to accelerate attainment of equilibrium. In many Instances the equilibrium constant for a given reaction in water does not adequately favor the desired product or water acts as an undesired reactant. Sometimes product can be favored using excess starting material, or by... 

Enzymes are catalysts, and thus small amounts can be readily detected. An enzyme having a turnover number of 300,000 s will provide an assay that is 300,000 times as sensitive as that for a structural protein, which must be assayed stoichiometrically, that is, as a single molecule. Many cellular proteins are produced in amounts that are too small to be detected by direct chemical methods. 

The molecular details of enzymatic reactions are currently of great interest and particularly so to kineticists because of the special kinetic problems involved. First, the complex mechanisms of enzymatic reactions require rather special phenomenological rate equations second, since enzymes are catalysts, the nature of catalysis in general must be considered and finally, the complex nature of even the simplest enzymatic mechanism makes its clarification a challenge. 

Many other groups of enzymes behave similarly they have evolved to take part in particular biochemical pathways, but they are sufficiently promiscuous that they will happily accept alternative substrates and provide chemically useful products from them. Enzymes are catalysts, like any other. In the next chapter, we take a more detailed look at those biochemical pathways and discuss the organic chemistry of life. 

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