The Chemistry of Alcohols in the Body

This blog article is a work of both Mr Adel Jeanne (Who did most of the work and research) and myself, both of us having a good relationship with wine.

Our passionate talks and discussions about the pleasures of alcohol led to the creation of this blog article since we deemed that before having a drink, it is imperative that one knows or has an idea about the Chemistry of Alcohol in the Body. 

According to the World Health Organization (WHO), 2.3 billion people are drinkers and Beer is the most consumed alcohol amongst Americans. From a glass of wine on New Year’s Eve to a coupe of champagne to celebrate an anniversary without forgetting the couple of beers with your mates, alcohol clearly helps us to socialize.

A lot of us have a strong affinity for alcohol, but how does it work in our body? Let us reflect on the following quote before indulging in the chemical sequence of alcohol in the body.

What is alcohol?

In chemistry, alcohols are organic molecules containing carbon (C), oxygen (O), and hydrogen (H) atoms and which possess at least one hydroxyl (-OH) functional group attached to a carbon atom. The chemical combination of 2 carbon atoms alongside with a hydroxyl (-OH) group and saturated with hydrogen atoms is known as ethanol.

Ethanol (or ethyl alcohol), a volatile and colourless liquid, is the main psychoactive ingredient present in alcoholic beverages and unfortunately for alcohol lovers, ethanol is the only ‘safe’ alcohol that we human can consume.
(Psychoactive: A psychoactive substance is one that affects how the brain works and causes changes in mood, thoughts, feelings or behaviour. Common examples are coffee, alcohol, heroin and cannabis.)

The chemical structure of ethanol can be viewed below and it is this simple organic molecule that takes us to very high levels of euphoria and in some typical cases, 🤮.

So now that we know what alcohol is and the alcohol that humans can consume 'safely', what characteristic of alcohol makes it soluble in the bloodstream?

The solubility of alcohol in the bloodstream

The hydrophilicity (explained below) of ethanol stems mostly from the presence of its terminal hydroxyl group and the shortness of its carbon chain, giving ethanol its polar character. The ability of ethanol to be transmitted all around the body is attributed to its small size and polar OH group, enabling ethanol to move across biological membranes in the body.       

Hydrophilicity: Hydrophilicity is the tendency of a molecule to be solvated by water. Surfaces that attract water are termed hydrophilic, whereas surfaces that repel water are termed hydrophobic.
Hydrophilic- Water-loving (polar species)
Hydrophobic- Water-fearing (non-polar species)

Polar: A polar molecule is a chemical species in which the distribution of electrons between the atoms is not even. We then say that this molecule contains both partially positive and negative charges as shown in the picture on the right. The most important polar molecule on Earth is water. In chemistry terms, we would say that it has a non-zero or net dipole.

Alcohol and your body

Once swallowed, the ethanol moves into your stomach and get easily absorbed in the bloodstream due to its attributes explained above. Your blood alcohol level will peak some 45 to 90 minutes later according to the NHS. This process occurs more quickly if:

•         you have an empty stomach
•          you are drinking a strong drink
•          the drink is carbonated
•          you are a woman
•          you are small

Have you ever experienced a throbbing headache accompanied by thirst and nausea after a huge drink?

In fact, your body considers alcohol as a poison (but which can be metabolised). It cannot be stored in our body which has to get rid of it promptly. This liver is a remarkable organ with more than 500 functions identified- one of its main roles is the conversion of alcohol into substances that can be stored or excreted. The breakdown of alcohol in our body occurs in 2 separate steps:

To metabolise: When you metabolise a substance, it is affected by chemical processes in your body so that, for example, it is broken down, absorbed, and used.

In the laboratory, the chemical conversion from ethanol to ethanoic acid, known as oxidation, can be easily carried out using an oxidising agent like potassium permanganate or dichromate in acidic conditions. (Outlined below)

 However, this is not how that conversion takes place in our body. In our body, the oxidation process takes place in the presence of enzymes and coenzymes. Coenzymes, like NAD⁺ (Nicotinamide adenine dinucleotide), act as biological oxidising agents that help the oxidation process by removing H and electrons. Your body is capable of breaking alcohol at a rate of 10 ml of 8 g per hour (the rate will vary from one individual to another).

The process is explained below:

The liver uses an enzyme called alcohol dehydrogenase, ADH1B, to oxidise ethanol to ethanal (acetylaldehyde) which is toxic to our body. Ethanal is one of the substances which are responsible for the symptoms of a hangover. Surprisingly, it is estimated that ethanal is 10 to 30 times as toxic as alcohol itself. Ethanal causes vasodilation (widening of the blood vessels which results from a relaxation of the smooth muscle cells), increasing the blood flow through your body and consequently leading to a decrease in blood pressure. Simultaneously, one starts to experience severe tension and headaches.

Therefore, it is very important that ethanal is further oxidised to ethanoic acid which is less harmful (the acid found in vinegar). The slower the rate of conversion from ethanal to ethanoic acid, the worse is the headache. The enzyme that converts ethanol to ethanal works much faster than the enzyme converting ethanal to ethanoic acid, hence a buildup of ethanal can occur when several drinks are taken in a row. Aldehyde dehydrogenase 2, ALDH2, is the enzyme which converts ethanal to ethanoic acid in the second step.

Eventually, the ethanoic acid is broken down to fatty acids, carbon dioxide or water (substances that are good for the body).

What happens when you consume too much alcohol?

When you have just started to drink, everything is cool, you feel relaxed.

At this stage, your body can process the ethanol into ethanal and the final conversion of ethanal to ethanoic at a sufficiently appreciable rate to prevent the build-up of the toxic ethanal in our body. Till now everything is good and you are in a good vibe!!

But then, with the drop in your ability to think about the chemistry of alcohols in your body, you start to drink more and more for a reason that only you and the Supreme Being is aware of. This is then when the real issue happens.

Due to a large amount of alcohol in your body, the proper and full conversion of ethanol to ethanoic acid is disrupted due to the difference in the rate of conversion that was explained above and there is the build-up of toxic ethanal in your body.

It is during this situation that at a party you hear one of your mates saying ‘I am not feeling well’ and this usually follows by the expulsion of the excess ethanal and ethanol and everything that was found in the stomach.

Then comes the real pain the next day with is commonly known as ‘hangover’.

And all these sums up to the following quote:

‘One should avoid drinking if one is not aware of the Chemistry of alcohols in the body.’ –A.J and C.G

Now that you are aware of the metabolism of ethanol in the body, let's find out how a bit about the response of the alcohol in your brain.

Neurotransmitters are chemical messengers that transmit the signals that control thought processes, behaviour and emotion throughout the body. Alcohol is a depressant, which means it slows down the brain and parts of the body.

Alcohol raises the activity of the inhibiting neurotransmitter gamma-aminobutyric acid (GABA). GABA triggers slow movements and slurred speech which is often seen in alcoholics.

The ‘good’ feeling occurs when alcohol elevates the release of the neurotransmitter dopamine, which is related to pleasure, in an area of the brain that is associated with all types of addictions.

The chemical structure of dopamine is shown below:

Also, PET (Position Emission Tomography) scan has demonstrated that alcohol releases endorphins- the “pleasure hormones” which binds to opiate receptors in the brain. (Click on the crosslink to learn more about research on endorphins.)
PET scan is basically an imaging test of the body. It involves the use of special chemicals known as radioactive tracers which are either swallowed or injected intravenously depending on the body part.
To learn more about PET scans, click here.

Well, this is the end of it and I hope this article raised your awareness about the Chemistry of alcohol in your body.

Cheers🥂.