Factors that Affect Enzyme Activity

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  • 0:00 What Is an Enzyme?
  • 1:14 Substrate Concentration
  • 2:27 Temperature and pH
  • 4:00 Cofactors and Coenzymes
  • 4:46 Inhibitors
  • 6:34 Lesson Summary
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Lesson Transcript
Instructor: Amanda Robb

Amanda holds a Masters in Science from Tufts Medical School in Cellular and Molecular Physiology. She has taught high school Biology and Physics for 8 years.

This lesson focuses on enzyme activity. We'll go over what an enzyme is and how it's used in the body. We'll also look at the different factors that affect enzyme activity, both positively and negatively.

What Is an Enzyme?

Sometimes during a tough study session, a snack really helps to keep the brain moving. Maybe something sugary, like a candy bar, cookie or caffeinated soda, is motivation to keep taking notes. But how does that sugar get from our mouths up to our brains to fuel critical thinking? The answer is through your digestive system. But for our organs, like the stomach, to do their jobs, their cells must make tiny proteins called enzymes.

Enzymes are proteins that speed up chemical reactions. They are needed to do all sorts of things inside our body, from getting rid of toxic compounds to breaking down food and making energy. Enzymes are like machines that make tasks easier for your cells. Just like a well-oiled machine works better than a rusty one, certain factors can make enzymes work better or worse. This is the focus of our lesson today. We'll be looking at five major factors that can affect enzyme activity, or how fast an enzyme can work.

Substrate Concentration

Let's say we're trying to saw some wood to make a table. We could hand saw it, but an electric saw would get the job done much faster. The saw is like our enzyme. The chemical reaction needed in the body might happen eventually, but with an enzyme, the reaction proceeds at the speed needed. But for us to get any work done using our electric saw, we need to have wood, which is the raw material. The raw material enzymes work on is called a substrate. If the cell doesn't have any substrate, the enzyme can't do its job.

Enzymes attach to substrates and make them into products. However, eventually, the enzymes in the cell will become saturated with substrate, meaning that they are working as fast as they can. At that point, no matter how much more substrate we add, the enzymes are at their maximum activity. For example, if we had one saw and 200 boards of wood, adding more boards of wood wouldn't make us able to saw them any faster.

Temperature and pH

Like people, enzymes like to work at a certain temperature. Too hot, and they will break apart, which is called denaturing. But, if they get too cold, they will essentially freeze and stop working altogether. Enzymes have an optimal temperature range, the range at which they work best, depending on where they are supposed to do their job. For example, enzymes in our bodies work best at body temperature, or 98.6 degrees Fahrenheit. However, bacteria that live in hot springs and hydrothermal vents have enzymes that work best at over 150 degrees Fahrenheit.

The amount of acid in a solution is called pH. The lower the pH, the more acid is present. The pH scale runs from 1 to 14, with 1 being the lowest pH, or the most acidic. Our stomachs are incredibly acidic, with a pH near 1. The optimal pH range for an enzyme, or the pH range at which it will have its highest activity, also depends on what environment it needs to work in. Our stomachs are host to many enzymes that exist best in a low pH. As we eat our snacks, these enzymes go to work breaking down the food. However, enzymes in the small intestine work best in an alkaline environment, or one with less acid and a higher pH.

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