Catalysts (Enzymes) — Overview & Examples

(Video) Function of Enzymes

by Study.com

Have you ever wished you had an enzyme's aid while building a snowman in the winter? Maybe not, but you will after watching this video. Watch and learn about an enzyme's job in biochemical reactions.

Something important to keep in mind about catalysts is that they only affect activation energy. They do not affect the amount of free energy in the reaction. That is, if a reaction releases 200kJ normally, it would still release 200kJ with an enzyme present.

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If you had trouble with this question, it might be a good time for a quick review of Chemical Reactions and Enzymes.

Speeding Up Reactions

Catalysts are substances that increase the rate of a chemical reaction. The catalysts do not undergo any permanent shape change and are not used up during the reaction.

Catalysts lower the activation energy of a reaction, written as (E$_a$) in the picture above. The energy of activation is the energy required to start a reaction. By lowering this barrier, reactions occur faster and easier.

Catalysts lower the activation energy barrier for chemical reactions to occur.

This can be thought of like trying to climb a large hill. If there is no catalyst present, you have to walk the whole way up the hill. Not only would it take forever, but it would be incredibly tiring. However, a catalyst would make the hill much less steep and also much shorter. This hill would be much faster and also less tiring.

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$\color{#8925AE}{\text{Enzyme}}$ : A protein that acts like a catalyst. It speeds up biological reactions but is not used up during the reaction

$\color{#8925AE}{\text{Activation Energy}}$ : Minimum amount of energy needed to begin a chemical reaction

$\color{#8925AE}{\text{Catalyst}}$ : A substance that speeds up reactions but is not used up during the reaction

$\color{#8925AE}{\text{Substrate}}$ : Molecules that a specific enzyme binds to and recognizes. They are transformed during the reaction

Enzyme Catalysis

Enzyme are proteins (chains of amino acids) that speed up chemical reactions.

Because they make reactions go faster, enzymes are called catalysts. (The process of speeding up a reaction is called catalysis).

Think of a normal chemical reaction as a road with a low speed limit. You can get from one end of the road to the other, but it will take a while.

An enzyme's job is to get rid of the speed limit and turbo-charge your car. Now you can get from one end of the road to the other way faster.

What Do Catalysts Do?

The amount of energy required for a chemical reaction to occur is called activation energy.

Enough energy has to be added to the reactants to get a reaction to start. It's like pushing a car up a hill: You have to keep adding more and more energy, but once you're at the top of the hill, the car (or the reaction) can begin to roll on its own.

It takes time to get enough energy to start a reaction. Catalysts shorten this time by reducing the activation energy required for a reaction to begin.

Compare the two reactions. The reaction with a catalyst has a much lower energy barrier to overcome. It takes much less energy (and less time) for that reaction to begin.

What Does This Look like in a Cell?

Now that we understand what catalysts do, it's time to apply that knowledge to enzymes. Image a cell as a room full of molecules flying around. When certain molecules collide, they cause a reaction. But, there's no way of guaranteeing they will ever come together. It could take seconds, or it could take days before they collide.

Mechanisms of Enzymes

Enzymes help make reactions go faster by bringing the required molecules closer together. This way, they will react more quickly. Enzymes have spots called active sites, which are specific to certain molecules (substrates). That is, only molecules which match the shape and size of the active site can bind to it. When they do bind, it creates the enzyme-substrate complex. In this form, the enzyme changes shape to fit the substrate even better. This specific fit is known as an induced fit. After the substrates react, they are released back into the surrounding environment.

Enzymes work by reducing the amount of time and energy needed for substrates to come together and reactions to occur. Without them, chemical reactions in the body would happen by chance, and they may not happen fast enough for cells to survive.

Key Vocabulary:

1. Enzyme
2. Protein
3. Activation energy
4. Catalyst
5. Enzyme complex

(Video) Enzymes and Catalysts

by Beverly Biology

Watch this video for a great explanation on what catalysts do, how they work, and how they are structured.