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Question Video: Applying Knowledge of Enzymes to Explain Why They Are Often Found in Washing Powders Biology • Second Year of Secondary School

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Why are enzymes often included in biological washing powders?

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Video Transcript

Why are enzymes often included in biological washing powders? (A) Enzymes can reduce the amount of water needed in a washing machine. (B) Enzymes help prevent the breakdown of clothing fibers, so clothes last longer. (C) Washing powders with enzymes smell nicer than washing powders without enzymes. Or (D) enzymes can help break down and remove stains caused by food.

In this question, we are expected to apply our knowledge of enzymes to answer the question. Questions that require you to use your knowledge to solve a problem tend to be a bit trickier than straightforward recalling of facts. With this question, it’s a good idea to rule out any answer that does not have anything relevant to the biological actions of enzymes. To help us to do this, we will first go over the key facts about enzymes. What is an enzyme and how does it work?

An enzyme is a biological catalyst that speeds up the rate of reaction without being used up itself. Catalysts work by lowering the activation energy needed to start the reaction. Let’s look at a couple of graphs to help illustrate this. We can see that more activation energy is required for the reaction to occur on the left, where there is no enzyme. The activation energy is much lower on the right in the reaction involving an enzyme.

Now let’s look at how enzymes lower the activation energy. Each enzyme has an area called an active site, which is specifically shaped to fit the substrate like a lock and a key fit together. This is called the lock-and-key model. First, a substrate molecule binds to the active site of the enzyme, which forms an enzyme–substrate complex. As the reaction completes, the enzyme releases the product. Since a bond was broken in this example, this could be a digestive enzyme.

Digestive enzymes are used for many different roles in science. Digestion is the breakdown of large insoluble molecules into small soluble ones. If we look at common biological macromolecules, we can see the bonds that digestive enzymes can break. In proteins, protease enzymes break peptide bonds between amino acids. In carbohydrates, carbohydrases break glycosidic bonds between monosaccharides. And in lipids, lipases break ester bonds between fatty acids and glycerol. Once digestion is complete, what is left are amino acids, monosaccharides, glycerol, and fatty acids. All these except for fatty acids are soluble in water. Fatty acids are soluble in soapy water.

So, let’s take what we know about enzymes and apply it to the question. It may not be immediately obvious which answer is right, but let’s review what we know about enzymes. They help catalyze reactions without being used up themselves. We have digestive enzymes in our bodies that digest food by breaking bonds in carbohydrates, lipids, and proteins to release the subunits, which are small, soluble molecules.

So the answer to the question “Why are enzymes often included in biological washing powders?” is answer choice (D). Enzymes can help break down and remove stains caused by food.

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