When a person drinks alcohol, it affects almost every part of their body. Beverage alcohol (i.e., ethanol) can change brain chemistry and become lethal in high doses. Ethanol is metabolized in the liver at a rate of approximately one drink per hour, with wide variation depending on conditions, including weight, gender, and food.
More specifically, after alcohol is ingested, it reaches the stomach where about 20% of the alcohol absorbs into the blood stream, through small blood vessels. The remaining 80% of the alcohol continues to the small intestine and is absorbed there into the blood stream.
The alcohol flows through the blood stream and is metabolized by the liver, where the alcohol is broken down by enzymes. The liver can, on average, metabolize about one standard drink (i.e. one 12 ounce bottle of beer, one 5 ounce glass of wine or 1.5 ounces of 40% alcohol) in one hour. Alcohol consumed in addition to these amounts can generally not be processed by the liver. When this happens, your blood becomes saturated and the additional alcohol makes its way to your body tissues and blood stream, until your liver can process the excess alcohol. (Source).
You can use B4UDrink, an initiative from The Century Council, to calculate Blood Alcohol Concentration (BAC) and learn more about how alcohol affects your body.
Alcohol can alter sleep patterns, basic motor function, and thoughts and emotions. Additionally, memory problems are fairly common among adolescents who consume alcohol.
Some studies have shown that moderate use of alcohol may have a beneficial effect on the coronary system. In general, for healthy people, one drink per day for women and no more than two drinks per day for men would be considered the maximum amount of alcohol consumption to be considered moderate use. For persons under the age of 21 there is no healthy or legal amount of alcohol.