Biochemistry, Toxicity

Biochemistry, Toxicity

When drinking alcohol, it diffuses to the blood easily because it is soluble in water and can enter the body with it. It enters the body from two ways.

1. The stomach: only a small percentage of alcohol diffuses into the blood via the stomach. alcohol is irritant to the stomach, so it affects its lining and might cause vomiting.

1. The small intestine: most of alcohol consumed enters the body through the small intestine.

Alcohol circulates in the blood. and since alcohol is considered a toxin to the body. the body needs to break it down. this process is done by the liver. so most of the alcohol consumed goes to the liver to be processed.

Effects on the liver:

The process of breaking down ethanol (alcohol) is to oxidize it to acetaldehyde with the help of alcohol dehydrogenase enzyme.

Acetaldehyde actually is 10-30 times more toxic than alcohol. also it is cocarcinogenic and mutagenic. Therefore, it has to be broken down.

The liver breaks it down acetic acid with the help of acetaldehyde dehydrogenase enzyme. In alcoholics, this process is slow due to the impaired function of liver from previous abuse.

Acetic acid as well is very toxic to the body, so the liver converts it to either [ CO₂ + H₂O ] or to fats depending on the energy needs.

this whole process will lead NAD⁺ to be converted to NADH. High NADH level will increase the glycerol 3-phosphate which will lead to an increase in the level of esterification of fatty acids. NADH inhibits the break down of fatty acids and help increase their synthesis.

Therefore, the liver needs NADH to be converted back to NAD⁺ . this can happen in the conversion of pyruvate to lactate (lactate dehydrogenase enzyme). so the liver will use the pyruvate in this process instead of using it in glyconeogenisis. Therefore, this will result in a decrease of the supply of glucose to tissues especially the brain. This is the reason for hangover (fatigue, weakness, mood disturbance, low attention and low concentration).

Effects on the Brain:

1. indirectly: no nutrition supply as mentioned above.

1. directly: alcohol itself is a depressant to the brain. It lowers the activity of the nervous system. the brain is divided to many region each responsible for some activities. those regions are connected by neurons. neurons communicate with each other via chemical and electrical signals. NTs (neurotransmitters) are responsible to convey the signal. Alcohol has effect on some NTs.

Most important NTs affected by alcohol:

• Glutamate: it is a excitatory NT. Alcohol affects it by inhibiting it leading to inhibition of signals.

• GABA: Inhibitory: Alcohol acts on the GABA receptors to facilitate their action leading to an enhanced inhibition.

• Dopamine: it is for rewarding process. it leads to code the experience or memory of alcohol, drugs, sex, food, etc in the cortex of the brain. this can influence promote subsequent behavior such as further consumption of alcohol. Alcohol activates the secretion of Dopamine.

• Serotonin: It is for rewarding process as well. It leads to mood compulsive disorders and aggression. It also is activated by alcohol.

Effects on the kidney:

Alcohol affects the function of the kidney. It impairs its ability to regulate the level of fluids by affecting the brain as mentioned above. It also induces the urine flow by:

1. Affecting ADH which will inhibit the reabsorption of fluids leading to large volume of urine to be excreted.

1. Affecting the level of pH in the body:

• It will lower the level of phosphate due to hyperventilation during withdrawal from alcohol.
• Alkalosis (low acidity) due to severe vomiting after binge drinking which causes loss of fluids, salts and stomach acid.