Enzymes - Video Tutorials & Practice Problems

Enzymes

In this video, we're going to begin our lesson on enzymes. An enzyme is defined as a molecule that catalyzes or speeds up a chemical reaction, and it's able to speed up the chemical reaction without being consumed by the chemical reaction, which means that the enzyme is not going to be altered by the end of the reaction. Now if we take a look at our image down below, notice that we're comparing a non-enzymatic reaction that has no enzyme to an enzymatic reaction that does have an enzyme. Notice on the left over here, what we're showing you are some reactants, the starting material or the ingredients for a reaction being converted into the products over here on the right, but notice that no enzyme is involved. And typically when there's absolutely no enzyme involved, then the reaction is going to occur really, really slow, too slow for life to be able to rely on reactions that do not have enzymes. And so, notice that over here on the right we're showing you the same reaction. And the same reaction over here we have, the substance being converted into the products. And this time, notice that an enzyme is present and the enzyme is represented by this structure that you see down below. And so the enzyme, its job, its function is to catalyze or speed up the chemical reaction so that it occurs much, much faster. You can see that the same reaction is able to occur at a much, much faster rate thanks to the enzyme, and so enzymes are all about catalyzing or speeding up chemical reactions. Now what's also important to note is that the term substrates is referring to the reactants of a chemical reaction that is catalyzed by an enzyme. If an enzyme is involved, then the reactants are referred to specifically as substrates. You can see that the substrates are pretty much the same exact thing as the reactants, and really the only difference is that substrates imply that an enzyme is involved, whereas reactants do not necessarily imply that an enzyme is involved. This concludes our brief introduction to enzymes and how they act as catalysts to speed up chemical reactions, and substrates are the reactants of an enzymatic reaction. We'll be able to get some practice applying these concepts as we move forward in our course, and we'll also get to learn a lot more about enzymes as we move forward. So, I'll see you all in our next video.

Functions of Enzymes

So now that we know that enzymes are catalysts and they speed up chemical reactions to make those reactions go faster, in this video, we're going to introduce some of the functions of enzymes. And so it turns out that enzymes actually have a wide variety of functions in living cells. And so we're not going to talk about all of the different functions that enzymes can have, but some of those functions include the following three functions that we're showing you down below. And the first is going to be building proteins. And so enzymes are involved with building proteins and making sure that proteins are built at a fast rate. And so you can see here that the enzyme is this little choo-choo-looking train here, and this choo-choo-looking train here is an enzyme that's called a ribosome, which is specifically going to be used to build proteins using messenger RNA, and we'll be able to talk about this process of building proteins later in our course. But for now, what you can see here is that enzymes are involved with building proteins, and you can see this here represents the enzyme, and it's building this protein that you see here. Now enzymes are also really, really important for copying DNA. And so here you can see in this image that the DNA is being copied or duplicated so that there are two copies of the DNA, and this is something that enzymes are involved with and help to make sure that this process occurs at a fast enough rate. Then last but not least, enzymes are also involved with the digestion of food. And so when we eat our foods, enzymes are involved with breaking down the foods that are in our stomachs. And so you can see over here, this represents a picture of our stomachs, and the food that is in our stomachs are going to be broken down using enzymes. And enzymes speed up the reactions that break down the foods that we digest. And so this here concludes our brief introduction to some of the functions that enzymes have, but the idea is that they are going to speed up chemical reactions and are involved with a wide variety of functions in living cells. And so I'll be able to see you guys in our next video.

Which of the following are examples of the functions of enzymes?

• A. A lactase enzyme breaking down lactose sugar in the small intestine.
• B. A DNA polymerase enzyme synthesizing new strands of DNA.
• C. A lipase enzyme breaking down fats (lipids) in the small intestine.
• D. A helicase enzyme unraveling DNA so it can be replicated.
• E. All of the above.

Environmental Factors Affecting Enzyme Activity

In this video, we're going to talk about some environmental factors that affect enzyme activity. Enzyme activity is defined as a measure of the amount of product that is produced by an enzyme in a certain amount of time. If an enzyme produces a lot of product within a given amount of time, then the enzyme has a lot of activity. But if the enzyme only produces a little bit of product within a given amount of time, then the enzyme only has a little bit of activity. Many environmental factors can actually affect an enzyme's activity. We're not going to discuss all of the factors that can affect an enzyme's activity, but 3 of those factors we are going to talk about are listed below. These include the temperature as the first environmental factor. The temperature can either include high temperatures, low temperatures, or just temperatures in between the two.

Another factor that could potentially affect the enzyme's activity is going to be the pH of the solution, whether the pH is acidic, neutral, or basic. Lastly, the third environmental factor that we're going to discuss that affects enzyme activity is the concentration of reactants. Depending on the concentration of reactants, the enzyme will have either high or low activity.

It's also important to recall from our previous lesson videos that several environmental factors, like high temperatures or even acidity, can cause a protein to denature. In most cases, enzymes are proteins. Thus, several environmental factors can also cause enzymes to denature. Recall that denatured proteins or denatured enzymes will lose their shape, and when they lose their shape, they lose their function. Since denatured enzymes lose their shape, they will therefore have decreased enzymatic activity.

Basically, what we're saying here is that the temperature needs to be just right for an enzyme to have optimal activity. If the temperature is too high or even too low, the enzyme will not have optimal activity. The same goes for the pH; it cannot be too low or too acidic, or too high or too basic; otherwise, it will affect the enzyme's activity. There needs to be a very specific pH for the enzyme to work optimally or at its best. The same goes for the concentration of reactants. If the concentration of reactants is too low, then the enzyme will not be able to produce a lot of products. And if the concentration of reactants is too high, then that could potentially oversaturate the enzyme and lead to the enzyme not working properly.

This concludes our introduction to how environmental factors can affect enzyme activity, and we'll be able to get some practice applying these concepts as we move forward in our course. So I'll see you all in our next video.

Enzymes Example 1

So here we have an example problem that wants us to complete this sentence here using one of these 4 potential answer options down below. And it says certain species of bacteria are able to perform metabolic reactions involving enzymes in hot springs where the temperatures are really hot because of which one of these reasons. Now the reason that bacteria are able to perform metabolic reactions in hot springs is because the enzymes that are involved are actually going to have optimal temperatures that are really, really high. So their enzymes have high optimal temperatures. And so these enzymes are going to work best in temperatures that are really really high. And so the correct answer here to this example problem is going to be option c. Now looking at some of the other options such as option b, it says, high temperatures make catalysis unnecessary, but really this is not true. Even in high temperatures, because the temperatures are high does not mean that catalysis is going to be unnecessary. So this is simply not true. And option d says that their enzymes are completely insensitive to temperatures, but this is also not going to be true. Enzymes are always going to be sensitive to their environments. And so these enzymes that have high optimal temperatures, if we were to remove these bacteria not work the same. So it's not that their enzymes are insensitive to temperature, it's just that their enzymes have high optimal temperatures. So option d here is not going to be correct. And then option a says that they are able to maintain a lower internal temperature, but bacteria that are in hot springs are really going to have the same temperature as their outside environment. And so this is really not going to be the reason for why these enzymes are capable of working properly in hot springs. And so once again, the correct answer to this problem here is because their enzymes have high optimal temperatures. And so that concludes this example and I'll see you all in our next video.

Which characteristics are likely associated with an enzyme isolated from a human stomach where conditions are strongly acidic.

• A. An enzyme that functions properly at 70 degrees Fahrenheit and at a neutral pH.
• B. An enzyme that functions properly at 98 degrees Fahrenheit and at an acidic pH.
• C. An enzyme that functions properly at 98 degrees Fahrenheit and at a neutral pH.
• D. An enzyme that functions properly at 70 degrees Fahrenheit and at an acidic pH.