Enzyme Activity - Review
1. What are catalysts?
Catalysts are substances that reduce the activation energy of a chemical reaction, facilitating it or making it energetically viable. The catalyst increases the speed of the chemical reaction.
2. What amount of catalyst is consumed in the reaction it catalyzes?
Catalysts are not consumed in the reactions they catalyze.
3. Is there a difference between the initial and the final energy levels in catalyzed and non-catalyzed reactions?
The catalysis does not alter the energetic state of reagents and products of a chemical reaction. Only the energy necessary for the reaction to occur, i.e., the activation energy, is altered.
4. What are enzymes? What is the importance of enzymes for living beings?
Enzymes are proteins that are catalysts of chemical reactions. From Chemistry it is known that catalysts are non-consumable substances that reduce the activation energy necessary for a chemical reaction to occur.
Enzymes are highly specific to the reactions they catalyze. They are of vital importance for life because most chemical reactions of the cells and tissues are catalyzed by enzymes. Without enzymatic action those reactions would not occur or would not happen in the required speed for the biological processes in which they participate.
5. What is meant by substrates of enzymatic reactions?
Substrates are reagent molecules upon which enzymes act.
The enzyme has spatial binding sites for the attachment of its substrate. These sites are called activation centers of the enzyme. Substrates bind to theses centers forming the enzyme-substrate complex.
6. What are the main theoretical models that try to explain the formation of the enzyme-substrate complex?
There are two main models that explain the formation of the enzyme-substrate complex: the lock and key model and the induced fit model.
In the lock and key model the enzyme has a region with specific spatial conformation for the binding of the substrate. In the induced fit model the binding of the substrate induces a change in the spatial configuration of the enzyme for the substrate to fit.
7. How does the formation of the enzyme-substrate complex explain the reduction of the activation energy of chemical reactions?
The enzyme possibly works as a test tube within which reagents meet to form products. With the facilitation of the meeting provided by enzymes it is easier for collisions between reagents to occur and thus the activation energy of the chemical reaction is reduced. This is one of the possible hypotheses.
8. On what structural level of the enzyme (primary, secondary, tertiary or quaternary) does the enzyme-substrate interaction depend?
The substrate binds to the enzyme in the activation centers. These are specific three-dimensional sites and thus they depend on the protein tertiary and quaternary structures. The primary and secondary structures, however, condition the other structures and so they are equally important.
9. What is the activation center of an enzyme? Is it the key or the lock of the lock and key model?
The activation center is a region of the enzyme produced by its spatial conformation to which the substrate binds. In the lock and key model the activation center is the lock and the substrate is the key.
10. Why can it be said that the enzymatic action is highly specific?
The enzymatic action is highly specific because only specific substrates of one enzyme bind to the activation center of that enzyme. Each enzyme generally catalyzes only a specific chemical reaction.
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