The Enzyme Rate of Reaction Equation

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  • 0:04 Rate of a Reaction
  • 2:15 Enzymatic Rate of Reaction
  • 3:30 Enzyme Rate of…
  • 4:39 Lesson Summary
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Lesson Transcript
Instructor: Darla Reed

Darla has taught undergraduate Enzyme Kinetics and has a doctorate in Basic Medical Science

This lesson discusses what rate means and how it relates to an enzyme reaction. It delves into ways of determining reaction rates as related to enzymes and describe the most common equation used to determine the rate of a reaction.

Rate of a Reaction

You must be 46 inches or taller to ride this ride. How many of you kept track of how tall you grew every month, striving to reach that 46-inch goal, and couldn't wait until you reached it so you could ride that super fun ride? You were measuring how tall you grew over time. This was your rate of growth. _Rate_ is simply one thing measured against another with different units. In this case, growth rate would be inches per month.

In chemistry, a reaction occurs when one thing changes to become something else; for example, when hydrogen and oxygen combine to form water. How fast one thing changes into another is known as the reaction rate or rate of reaction. In this example, the rate of reaction would be how fast hydrogen and oxygen combine to form water. Of course, the reverse reaction also has a rate as well: how fast water is changed into hydrogen and oxygen.

Rates of reaction are often dependent on a variety of factors, like temperature, pressure and pH. Since many of these factors are kept constant, scientists have termed the lowercase letter k to stand for the rate constant, which includes the aforementioned factors. With these factors constant, the only factor left affecting the rate is the amount of substance used or product formed.

Thus, the rate of a reaction can be calculated by multiplying the rate constant by the substrate concentration (amount) or by determining reaction velocity (V). In physics, velocity refers to the rate at which something changes in position over time. In biochemistry, velocity can be used to refer to the amount of product formed over time and is often used synonymously with rate of reaction.

Let's say you're making a cake. The temperature and pressure in the room won't change. What will change is the amount of ingredients and amount of cake batter being formed. Stirring changes the ingredients into cake batter. The rate depends on how fast you can mix the ingredients, which also depends on how much of the ingredients you have and what you use to mix it. If you stir them with a spoon, they will eventually mix together, but it's going to take a lot of stirring.

Enzymatic Rate of Reaction

What could make the ingredients mix faster? An electric mixer. An electric mixer speeds up the formation of cake batter. The beaters on your electric mixer act as enzymes. Enzymes are proteins that speed up the rate of reaction by lowering the amount of energy required for a reaction to take place while remaining unchanged themselves. By using the electric mixer instead of a spoon, you have to do less work and the ingredients get mixed faster. If your mixer has two beaters the work will get done at an even faster rate.

The place on all enzymes where chemical reactions happen faster is known as the active site. The bottom of the beaters act as the active site, changing ingredients into cake batter. The substance that binds, or attaches, to the active site is called a substrate. The substance that is formed is called the product.

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