Your Body: The Liver & Alcohol

Happy New Year, molecular buddies! You may have noticed that this blog is a little late in getting back on track this January, I very much wish I could say that this was due to over-indulging at Christmas and being too full of turkey and cake to write. However, instead, rather more boringly, I caught a nasty little virus the weekend before Christmas and have spent the past fortnight in bed, coughing, hating my sinuses and noticeably not writing. But it’s okay, I did still eat All The Turkey and All The Cake, plus I’m back now, and there’s still plenty of January to be getting on with! Woohoo!

December’s post on the kidneys (as requested by gorgeous Bella) proved to be so popular that I have decided to try it out as a series of posts on the way your body does really awesome and amazing things.  Next up? Your liver.

Your liver is unbelievable, truly, it does SO MUCH STUFF. It’s responsible for an incredibly wide range of things in the body. As a result of this it has won Best Multi-Tasker Award at The Association of Human Organs Recognition of Excellence Awards since it first evolved in vertebrates, which was a really long time ago. Also as a result of this, the liver is too complicated to tackle in one single post. I’d still be writing it in March and you’d all have wandered off somewhere else to have a party without me. Probably. However, what better way is there to start exploring the liver than by looking at the most January-appropriate of its functions, the processing and breakdown of alcohol?

Have you ever wondered how your body gets rid of alcohol? That might seem an odd question, but just as I always think it’s fascinating to understand how things affect your body at a molecular level, it’s equally incredible to look at how your body can affect, change and process them in turn.  Alcohol acts on receptors in your brain to cause its effects, but your liver is responsible for clearing the alcohol away.

When you drink alcohol it is absorbed into your bloodstream from your digestive system, from your bloodstream it can get into your brain, where it makes you think you’re really good at dancing, amongst other things. Alcohol pretty much stays in your bloodstream, having a whale of a time, living it up; until your body has a chance to process it, which is almost entirely the responsibility of the liver. Although up to 10% of the alcohol may leave the body on your breath, in your urine or in your sweat; your liver is still in charge of dealing with 90-98% of the alcohol in the body.  And once your alcoholic blood reaches your liver, the party abruptly halts as it encounters an enzyme: alcohol dehydrogenase (ADH).

ADH hates alcohol; they have a long-running feud, much like Robin Hood with all the rich folk, except ADH is a lot more efficient than any renegade heroic outlaw. It almost never wears green tights either; but whenever it comes across alcohol, it does ruthlessly yank electrons away, and donate them to the co-factor NAD+. This reaction turns the electron-poor NAD+ into NADH, a co-factor rich in electrons, and turns the alcohol into an acetaldehyde molecule instead.

Alcohol dehydrogenase: the Robin Hood molecule.

Alcohol dehydrogenase: the Robin Hood molecule.

The downside of this zealous electron-stripping is that acetaldehydes are highly unstable molecules, and are toxic to your liver; by robbing electrons from the rich, ADH has created something worse. Luckily, ADH isn’t alone, he has a band of merry enzymes and one of them, acetaldehyde dehydrogenase (ALDH), very quickly turns acetaldehyde into acetic acid. Acetic acid, luckily, is fairly harmless in relatively small amounts and can either be used by the body to build fatty acids or can be further broken down by the rest of the band of merry enzymes until there is nothing left but carbon dioxide and water. Phew.

With its army of Robin Hood molecules, the liver can process roughly 15ml of alcohol per hour, so if you drink at a faster rate than your liver can work, you start to feel drunker; the amount of alcohol partying away in your system races upwards, and the rate of the downward slope never changes. This is also why if you drink a very large amount, you can still be drunk the next day, no matter what time you actually stopped drinking.

And there you go, that’s how your fantastic multi-tasking liver deals with the task of detoxifying alcohol from your body, with molecules in green tights and a band of merry enzymes. Naturally.

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6 thoughts on “Your Body: The Liver & Alcohol

  1. I love the Robin Hood analogy and your explanation of the electron trading going on between NAD+ and NADH, so many biological cell processes are based on electron transfer. Maybe you can explain what respiration really is next time.
    Have you ever taught or becoming a teacher? You remind me of my best biochemistry professor, the one who would explain kinetics and other complicated subjects like activation energy or effective shocks in terms of parties full of people, crammed together, saying that you were more likely to meet Mr. Right at a multitudinary party than at one that was rather empty, and that sometimes bumping into people (like that cliched scene where a girls throws her books at the floor and a handsome guy comes to the rescue) is all you need to get things started.
    One of my most memorable chemistry exercise sessions was when we had to chart and graph how long it takes for alcohol to leave the body based on blood levels. I never forgot that women can drink proportionately less alcohol than men (less weigh = less enzyme) and that Asian people have some kind of mutation in the AlDH or ADH which means they really have trouble tolerating alcohol.
    You didn’t mention that acetic acid is in fact what we more commonly call vinegar.
    Have a good week ! We should email to organize a meetup in London (or Brighton)…

    • Thanks Amanda, I love the sound of your biochem professor, I remember my Mum once describing ionic and covalent bonding in terms of different levels of kissing at a party. It has always stuck in my mind!

      Definitely true that many Asian people have with alcohol, a large proportion of them carry a slightly faulty ALDH enzyme, meaning that if they drink they get high build-up of acetaldehyde, causing flushed face, nausea, dizziness etc.

      K x

      PS: Totally forgot to email you, I will get on that now. Thanks!

  2. I really like this post and feel I understand a lot more now and was going to follow up by asking which of the enzymes is mutated in many of my Asian friends meaning they cannot drink (well they can but it is a horrendous experience for them) and there it was in the comments. Thanks!

  3. Pingback: (Two) Weekly Round-Up | scicommnetwork

  4. Love the analogy (as always)…I second the comment that you would make an excellent teacher…or writer of textbooks…or life guru…or anything really…. (fangirl, me? Um, yeah okay, that’s fair)

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