Ethanol Absorption and Metabolism Alcohol Metabolism. Ethanol Absorption and Metabolism Alcohol Metabolism Ethanol is absorbed in the small intestine and metabolized by the liver. The major pathways of ethanol metabolism are oxidation to acetaldehyde, conjugation with glucuronic acid, and finally excretion in the urine. Acetaldehyde is a carcinogen, but it is also converted to acetate, which is used for energy by the body.
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The human body can quickly metabolize ethanol, which is why most people feel little or no effects from drinking alcohol. Once absorbed into the bloodstream, ethanol is distributed to all parts of the body. The liver breaks down ethanol into acetaldehyde and carbon dioxide, which are then expelled through the breath and urine. Acetaldehyde levels rise as the alcohol is consumed, but they eventually fall and are eliminated from the body.
Alcohol is a central nervous system depressant. It is absorbed into the bloodstream and travels to all parts of the body. It is eliminated from the body in several ways, including through the liver, the breath, and urine. The amount of alcohol that is metabolized determines how intoxicated someone is.
Metabolism of ethanol in liver
Hey everyone, this lesson is on ethanol absorption and metabolism. So in this lesson, we’re going to talk about factors that affect the rate of absorption of ethanol, and we’re also going to get into a step by step analysis of pathways involved in ethanol metabolism. So when we ingest ethanol, there’s a couple of factors factors that affect the rate at which ethanol is absorbed. One of those is the gastric emptying rate or the rate at which our stomach empties its contents. The other is ethanol concentration.
So with the gastric emptying rate, an empty stomach, such as during times of fasting, would actually increase the gastric emptying. So on an empty stomach, when we ingest ethanol, we actually increase the rate of absorption because the gastric emptying rate has increased. Now, any foods, such as carbohydrates, fats, and proteins will actually reduce the rate of gastric emptying, which would reduce the rate of alcohol or ethanol absorption. So when the ethanol is absorbed, it enters into the portal vein and travels to the liver. Now, in the liver, it undergoes a specific effect known as the first pass metabolism or the first pass effect.
Now, firstpast metabolism is metabolism of ethanol before it reaches the systemic circulation, and this occurs in the liver. Now, this actually is higher in men than women, and this is one of the reasons why men, on average, can tolerate alcohol a bit better than women. So when ethanol does get absorbed into a cell, it does so by passive diffusion. And passive diffusion itself is related to the ethanol concentration, which means that with increasing ethanol concentration, you have an increased rate of diffusion. So all of these factors affect the absorption of ethanol.
When ethanol is absorbed in the body, there are two primary locations where ethanol is metabolized. One is in the lining of the stomach. However, the vast majority of ethanol metabolism occurs in the liver. So since the stomach lining contributes very little to metabolism of ethanol, we’ll focus mostly on liver metabolism of ethanol. The metabolism of ethanol begins with the enzyme alcohol dehydrogenase, or ADH, which processes the ethanol into acetaldehyde.
Alcohol metabolism biochemistry
Now, this enzyme requires NAD plus as a cofactor, and what it does is when the ethanol is processed into Ecstaldehyde, the NAD plus is actually reduced to an aid. Nadh and alcohol dehydrogenase require zinc as a cofactor for its function as well. Now, there are several classes of alcohol dehydrogenase, and class one is by far the most important in ethanol metabolism.
Class one has the highest affinity for ethanol, so the majority of ethanol is actually metabolized via class one alcohol dehydrogenase and the liver. However, it’s important to note that class two and class three both have important roles to play in ethanol metabolism, especially during high concentrations of ethanol.
So class two and class three alcohol dehydrogenase actually have a lower affinity for ethanol. But when ethanol concentrations are very high, class two and class three become more important and they can actually bind to ethanol more readily and actually help to process ethanol into acetaldehyde.
So when ethanol is processed into acetaldehyde, acetaldehyde is a very important chemical because it is actually toxic and it is actually associated with the hangover symptoms that people experience after ingesting ethanol. Now, acetaldehyde can actually leave the liver and enter the bloodstream and have other toxic effects on other tissues. So it’s very important for the liver to get rid of this chemical.
And the way it does it is that it actually utilizes another enzyme. And that enzyme is aldehyde dehydrogenase. And this enzyme is actually located in the mitochondria. And what it does is it actually metabolizes acetyldehyde to acetate. And again, this process requires NAD plus as a cofactor, and it reduces NAD plus to NADH.
Now, the alcohol dehydrogenase reaction is irreversible as opposed to the alcohol dehydrogenase reaction, which is a reversible reaction. Now, there’s a medical condition that is associated with although dehydrogenase enzyme in that condition is known as alcohol flush response or the alcohol flush reaction, which is also known as the Asian flush syndrome.
Now, in this syndrome, this syndrome is actually due to a deficiency in aldehyde dehydrogenase two enzyme. And what happens in this syndrome is that deficiency in this enzyme leads to an increase or a build up in a Ctlddehyde, which actually causes induces catecholine release, which causes that characteristic flushing response in the skin of people that are affected. This condition is typically found in people of Asian descent.
Alcohol metabolism ppt
Now, once we have acetate produced from acetaldehyde via the enzyme aldehyde dehydrogenase, the acetate can either leave the liver, enter the blood, and be picked up by peripheral tissues, or it can actually stay in the liver. And in either case, if it gets picked up by peripheral tissues or it stays in the liver, it can be processed into acetylCoA. And this involves a couple of different enzymes. It can be processed by the enzyme acetylCoA synthesize or Acylcoais synthase, too, depending on if the acidate is in the mitochondria or in the cytosol. As more and more ethanol is metabolized, more and more NADH is produced.
The alcohol dehydrogenase reaction is a reversible reaction that occurs in the cytosol and it leads to an increase in cytosol NADH. The Albany dehydrogenase reaction is an irreversible reaction that occurs in the mitochondria. And this leads to an increase in mitochondrial NADH. And as more and more ethanol is metabolized, more and more acetate and more and more acidic away will be produced and will get an excess of acidical A. And finally, this metabolism pathway is responsible for approximately 90% of ethanol metabolism.
The remainder of ethanol metabolism is accomplished by the microsomal oxidation system. Microsomal oxidation of metabolism of ethanol also occurs in the liver, and it occurs by the enzyme CYP two, E one, which is a cytochrome P 450 enzyme. So Cytophone P 452 E one, and this is located in the smooth endoplasmic reticulum this enzyme will actually process the ethanol into acetaldehyde. Now, it’s important to note that CYP two E one is not a major contributor to ethanol metabolism. In fact, it becomes very important when ethanol concentrations are very high.
Alcohol metabolism enzyme
So normally most of the ethanol metabolism occurs with alcohol dehydrogenase. But when we have situations where the ethanol concentrations are very high, this enzyme becomes extremely important to remove excess ethanol. Now, one important aspect of CYP two E enzyme is that it produces reactive oxygen species, or Ros. And this can be a problem when a lot of ethanol is being metabolized. Now, reactive oxygen species itself, especially at higher levels, can cause DNA damage and other organelle problems such as mitochondrial dysfunction.
So it’s a very toxic byproduct to the cell. And what’s interesting about the CYP Two E one enzyme is that when this enzyme is exposed to high levels of ethanol over long periods of time, It can actually be up regulated. So it’s actually one of the mechanisms the upregulation of this enzyme is actually one of the mechanisms by which people can gain tolerance to alcohol. And it’s known to actually be higher in people with problems with alcoholism. So SC taldehyde can be processed with the same enzyme, Cop two, we want to acetate again producing Ros, but by far, the majority of the acetaldehyde is actually metabolized by Aldehydehydrogenase to acetate.
Ethanol metabolism pathway
So CIP Two E one is not as important for acetyl dehyd metabolism as Aldehyde dehydrogenase is. And again, when we use Aldehyde dehydrogenase, we are again producing an NADH from the reaction. And the two acetates can also be processed into acetylCoA. Now, again, this leads to high levels of NADH and high levels of acidic away. This type of metabolism accounts for approximately 10% of ethanol metabolism.
Ethanol Absorption and Metabolism Alcohol Metabolism When we look at total ethanol metabolism, the metabolism from the pathway involving alcohol dehydrogenase and this pathway involving CYP Two E one, both pathways together culminate in a total rate of ethanol metabolism of 7 grams/hour in an average person, which is about one alcoholic drink per hour.
Anyways, guys, that was a lesson on ethanol absorption and metabolism. I hope you found this video helpful in the next lesson. We’re going to talk about the consequences of ethanol metabolism and we’re going to look into other cellular metabolic pathways and see how ethanol metabolism affects those pathways. And anyways, if you like this video, please like and subscribe for more videos like this one.
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Ethanol Absorption and Metabolism Alcohol Metabolism
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Cconclusion
it is clear that ethanol absorption and metabolism play an important role in the intoxication process. Abusers need to be aware of how their body processes ethanol in order to avoid getting intoxicated quickly.
