Enzymes

Front 1

What are catalysts?

Back 1

Catalysts are substances that reduce the activation energy of a chemical reaction. The catalyst increases the speed of the chemical reaction

Front 2

How much of the catalyst is used up when it catalyses a reaction?

Back 2

Catalysts are not consumed in the reactions they catalyze. They are free to react again.

Front 3

What are enzymes?

Back 3

Enzymes are proteins that are catalysts of chemical reactions. They reduce the activation energy necessary for a chemical reaction to occur. Enzymes are highly specific to the reactions they catalyze.

Front 4

What is meant by substrates of enzymatic reactions?

Back 4

Substrates are the molecule that the enzyme acts on. Enzymes and substrates bind forming an enzyme substrate complex.

Front 5

Describe the difference between the "lock and key" and the "induced fit" model for enzyme action.

Back 5

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.

Front 6

On what structural level of the enzyme (primary, secondary, tertiary or quaternary) does the enzyme-substrate interaction depend?

Back 6

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, determine the tertiary and quaternary structures and so are also important.

Front 7

Why can it be said that the enzymatic action is highly specific?

Back 7

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.

Front 8

What happens to a denatured enzyme regarding its functionality? How can that result be explained with the help of the lock and key model?

Back 8

According to the lock and key model the enzyme functionality depends on the shape of the active site. After the denaturation the shape of the active site is changed and the enzyme loses its catalytic activity.

Front 9

What are the main factors that alter the speed of enzymatic reactions?

Back 9

The main factors that change the speed of enzymatic reactions are temperature, pH and substrate concentration (quantity).

Front 10

How does the substrate concentration affect the speed of enzymatic reactions?

Back 10

Initially as substrate concentration increases, the speed of the reaction increases; this happens because free active siters of the enzyme bind to free substrates. Once all the active sites of the available enzymes become bound to their substrates new increments of the substrate concentration will have no effect on the speed of the reaction.

Front 11

How does temperature affect the action of enzymes upon their substrates?

Back 11

There are defined temperature ranges under which enzymes operate and there is a specific temperature level (optimum temperature) in which enzymes have maximum efficiency. Therefore temperature variations affect enzymatic activity and the speed of the reactions they catalyze.




In addition, as proteins, enzymes can be denatured under extreme temperatures.

Front 12

What are enzyme cofactors?

Back 12

Some enzymes need other associated molecules to work. These molecules are called enzyme cofactors and they can be, for example, organic ions like mineral salts, or organic molecules.