Other Types of Liquid Chemicals - Online Tutor, Practice Problems & Exam Prep

Heavy metals like silver, arsenic, zinc, and copper are effective disinfectants at low concentrations due to their ability to denature proteins by interacting with sulfhydryl groups. Phenolic compounds, derived from phenol, disrupt cytoplasmic membranes and denature proteins, with applications in products like Listerine and Lysol. Peroxygens, such as hydrogen peroxide and paracetic acid, serve as strong oxidizing agents that can sterilize but are toxic at high concentrations. Understanding these compounds is crucial for controlling microbial growth and preventing infections.

Heavy Metal Compounds

In this video, we're going to begin our lesson on other types of liquid chemicals used for controlling microbial growth, starting with the heavy metal compounds. Heavy metals are really just metals with relatively high densities, atomic numbers, or atomic weights. Heavy metals include silver, arsenic, zinc, and copper, which can be used as disinfectants at very low concentrations. The reason these heavy metals need to be used at low concentrations is that, at high concentrations, they are actually extremely toxic to humans. They can also pollute natural waters like lakes and oceans, so it's best for them to be used only in low concentrations. These heavy metals have the ability to denature proteins, which recall just means that they are going to cause the proteins to lose their shape and function. These metals can do that by interacting with the sulfhydryl groups on proteins, or the SH groups on proteins, which will change their structure and denature the protein. Specifically, silver-containing antiseptics can be used to prevent infections on the skin of humans.

If we take a look at our image down below, notice we're showing you an image of these heavy metals which can once again be used as liquid chemicals to control microbial growth. We're showing you a bunch of different examples of heavy metals such as copper, zinc, arsenic, and over here, we're showing you silver. Silver-containing antiseptics can once again be used as antiseptics to treat wounds or infections on the skin.

This here concludes our brief introduction to the use of heavy metal compounds as liquid chemicals for controlling microbial growth, and we'll be able to get some practice and learn more about other types of liquid chemicals as we move forward in our course. I'll see you all in our next video.

Heavy metals are no longer used to prevent microbial growth in cooling water primarily because:

• A. Antibiotics are cheaper.
• B. Other chemicals were shown to be much more effective.
• C. Microbes developed resistance to these metals.
• D. Their use contributes to serious pollution of natural waters.

Phenolic Compounds

In this video, we're going to continue to talk about other liquid chemicals for controlling microbial growth by briefly focusing on phenolic compounds. And so these phenolic compounds or just phenolics for short, as their name implies, are really just a class of chemicals that are derived from a molecule known as phenol. And so this phenol molecule really just consists of a benzene ring bound to a hydroxyl group or an OH group. And so if we take a look at our image down below, notice on the left-hand side over here we're showing you an image of the molecule phenol. And again, this molecule phenol consists of this benzene ring that you see highlighted here in green with a hydroxyl group or an OH group attached. And again, these phenolics or phenolic compounds are going to be molecules that are derived from this phenol molecule. Now, it turns out that a scientist of the name Joseph Lister was actually the first to employ phenol as an antiseptic or a disinfectant. And so down below what we have is an image of Joseph Lister. Now since Joseph Lister first employed these phenols, they have been used commonly in many different types of products and in fact, the oral antiseptic Listerine was actually named after Joseph Lister. Also, phenolics are the active ingredient in the common household disinfectant called Lysol. And so if you use Lysol in your house again, to disinfect, then you can remember that there are phenolics in there. And so down below what we have is an image of this bottle of Listerine, the oral antiseptic, and also a bottle of the Lysol, which again you could use in your house as a disinfectant. Now, the way that these phenolics are able to control microbial growth is because the phenolics are able to disrupt cytoplasmic membranes and denature proteins. And so by doing so, they are able to kill the cells and control the microbes. And so, this here concludes our brief introduction to the phenolic compounds or phenolics and we'll be able to get some practice applying these concepts as we move forward. So I'll see you all in our next video.

Peroxygens

In this video, we're going to continue to talk about other liquid chemicals used for controlling microbial growth by specifically focusing on peroxygen. Peroxygen are a group of molecules that serve as strong oxidizing agents. Recall from our previous lesson videos that oxidizing agents are going to cause other molecules around them to become oxidized or lose electrons. These peroxygens that serve as strong oxidizing agents can actually be used as sterilants when used appropriately to kill all microbes, except for prions of course. However, they can also be really toxic to humans at high concentrations. Thus, they must be diluted and used at low concentrations in order to be used safely. Now, some common examples of peroxygens include peracetic acid, whose chemical formula is C2H4O3, and hydrogen peroxide, whose chemical formula is H2O2. Now, peracetic acid, which is again C2H4O3, is actually a lot more potent, a lot more powerful of a chemical disinfectant and sterilant than hydrogen peroxide. However, peracetic acid, even though it's more potent, it's also more irritating to the skin and the eyes. So, it has some advantages and some disadvantages as well. Now, hydrogen peroxide is commonly used at low concentrations, once again, because at high concentrations it can be toxic. It's used at low concentrations specifically on the skin, to prevent infections. Some of you that may have had injuries in the past may have used hydrogen peroxide to help control the microbial growth around your injury. These peroxygens, peracetic acid, and hydrogen peroxide, are going to disrupt cytoplasmic membranes and denature proteins as well. That is really how they can damage microbes and destroy microbes for controlling microbial growth. It's also worth noting, from our previous lesson videos, you should recall that some microbes have the enzyme called catalase. Catalase is the enzyme that will convert hydrogen peroxide to water and oxygen. That is basically converting hydrogen peroxide into chemicals that are not really toxic to the microbe. So, hydrogen peroxide is a less effective disinfectant than peracetic acid because some microbes that have this enzyme catalase, are able to convert it to water and oxygen, and therefore they're able to survive in lower concentrations of hydrogen peroxide. If we take a look at this image down below, we can see these peroxygens. On the left-hand side, we're showing you the chemical structure for peracetic acid. Again, you can see that its chemical formula is C2H4O3 and its chemical structure is right here. This little corner here represents a carbon atom. Then we have the chemical structure for hydrogen peroxide, whose chemical formula is H2O2, and you can see its structure right there. This is a bottle of hydrogen peroxide that you may have in your home for treating some of your wounds. Again, some cells have this enzyme called catalase, which can convert the hydrogen peroxide into water and oxygen gas. This is why hydrogen peroxide is not as potent as peracetic acid. But this here concludes our brief lesson on peroxygens and how they are used as liquid chemicals for controlling microbial growth, 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.

Which chemical are all phenolic chemicals a derivative of?

• A. Hydroxyl.
• B. Ethanol.
• C. Aldehyde.
• D. Phenol.
• E. Benzene.

Which of the following is not considered a peroxygen?

• A. Hydrogen peroxide.
• B. Phenol.
• C. Peracetic acid.
• D. All are peroxygens.