Using Alcohol as a Disinfectant and Antiseptic

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  • 0:05 The Pros and Cons of Alcohol
  • 0:40 Types of Alcohol
  • 1:58 Mechanism of Action
  • 4:40 Ideal Concentrations
  • 5:38 Lesson Summary
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Lesson Transcript
Instructor: Artem Cheprasov
This lesson will discuss how alcohol can be used as a disinfectant and antiseptic but not a sterilant. We'll also talk about what it kills and doesn't kill and why ethyl alcohol and isopropyl alcohol are the two most commonly used alcohol-based disinfectants.

The Pros and Cons of Alcohol

Alcohol: as one famous man once said, it's the cause of, and solution to, all of life's problems. That man was none other than Homer Simpson, of course. I can sit here and make an entire lesson out of quotes and jokes about alcohol. However, in this lesson, I'll try to focus in on the effects alcohol has on microbes. Never mind the effects it has on you, such as headaches, loss of consciousness, severe liver damage and premature death. Those aren't all that important.

Types of Alcohol

The first important thing we need to talk about is the different types of alcohol available for use. Now, don't get excited; this doesn't mean we'll be going on a trip to the liquor store any time soon.

We'll be talking about the types of alcohol that are used as a disinfectant or an antiseptic. Those aren't the same thing, by the way. Disinfection implies the death of most microbes on an inanimate object, while antisepsis implies the death of most microbes on living tissue, such as your skin.

The difference is slight but still important. You can liken disinfection to a bacterium passing out on a floor, which is an inanimate object, while antisepsis implies that a bacterium passes out on a living friend after having too much from the tap after work.

Anyways, these bacteria and other microbes can drink several different types of alcohol, including:

  • Ethyl alcohol: a type of alcohol commonly known as ethanol or grain alcohol
  • Isopropyl alcohol: an alcohol that is sometimes referred to as rubbing alcohol
  • Methyl alcohol: an alcohol that is also called methanol or wood alcohol

Mechanisms of Action

Methyl alcohol is very rarely used compared to rubbing alcohol or ethanol in medicine because it's quite weak compared to the latter two when it comes down to disinfection and antisepsis. It's like a light beer compared to whiskey or vodka. Hence, we will just focus in on rubbing alcohol and ethanol as we move on in this lesson.

The way by which these two alcohols destroy bacteria, viruses and fungi is through something known as protein denaturation. In basic terms, it's a process whereupon a protein loses its higher-order structure. You can imagine that a protein is like a piece of metal. That piece of metal can be formed into many different things. For example, it can be made into a paperclip. The shape of the paperclip is like that metal's higher-order structure. If you were to physically unwrap and uncoil that paperclip into a straight piece of metal, you would have metaphorically denatured it.

When you uncoil that paper clip, it is still a piece of metal, but it has lost its function. It can no longer hold paper together. Likewise, when a protein is denatured by an alcohol, it's still a protein, but it cannot perform the function it once could. Well, if the bacteria, viruses, and fungi cannot rely on their proteins to do their job, they simply die.

Another way by which alcohol can kill is by damaging the outer membrane of bacterial cell membrane. It's like damaging your skin. If you lost all of your skin, you would die, since you would be unable to protect yourself from the dangers of the environment around you. Likewise, if you damage or dissolve the cell membrane of bacteria, they cannot protect themselves either and end up dying in the process.

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