How coffee keeps us awake?

Coffee plant originated in Africa and Madagascar. Coffee has become a universal and almost indispensable beverage in the modern dietary. Coffee provides a energy burst as it contains caffeine. Caffeine helps rev up metabolism, increases endurance, improves focus and lessens pain.

History of coffee

The coffee plant, which was discovered in Ethiopia in the 11th Century, has a white blossom that smells like jasmine and a red, cherry-like fruit. Back then, the leaves of the so-called 'magical fruit' were boiled in water and the resulting concoction was thought to have medicinal properties. As the fame of the coffee plant spread to other lands, its centuries-long voyage was about to begin.
Coffee spread quickly through the Arabian Peninsula. In the mid 14th century, coffee cultivation reached Yemen and for 300 years, it was drunk following the recipe first used in Ethiopia. Yemen's climate and fertile soil offered the ideal conditions for cultivating rich coffee harvests.
Istanbul was introduced to coffee in 1555 during the reign of Sultan Suleiman the Magnificent by Özdemir Pasha, the Ottoman Governor of Yemen, who had grown to love the drink while stationed in that country. © turkishcoffeeworld

Composition of coffee

Coffee contains about 1500 chemicals. The different groups of chemicals present in coffee are –
150 Aliphatic compounds, 56 Carbonyl compounds, 9 Sulfur containing compounds, 20 Alicyclic compounds, 10 Ketones, 60 Aromatic benzenoid compounds, 16 Phenols, 300 Heterocyclic compounds, 74 Furans, 10 Hydrofurans, 37 Pyrroles, 9 Pyridines, 2 Quinolines, 70 Pyrazines, 10 Quinoxalines, 3 Indoles, 23 Thiophens, 3 Thiophenones, 28 Thiazoles, 28 Oxazole.
Coffee contains huge numbers of compounds. About 800 - 1000 aroma compounds caffeine, carbohydrates, chlorogenic acids, trigonelline, lipids, melanoidins, volatile compounds.

How coffee keeps us awake?

It's a normal practice to drink coffee to stay awake. Here is how it works.
Caffeine present in coffee works by changing the chemistry of the brain. It blocks the action of a natural brain chemical, adenosine, that is associated with sleep. The binding of adenosine with the brain causes drowsiness by slowing down nerve cell activity. In the brain, adenosine binding also causes blood vessels to dilate (presumably to let more oxygen in during sleep). Adenosine are produced by our daily activity.
Caffeine and adenosine look similar. Caffeine, therefore, binds to the adenosine receptors. However, it doesn't slow down the cell's activity as adenosine would. The cells cannot sense adenosine anymore because caffeine is taking up all the receptors adenosine binds to. So instead of slowing down because of the adenosine level, the cells speed up. Caffeine also causes the brain's blood vessels to constrict, because it blocks adenosine's ability to open them up. This effect is why some headache medicines, like Anacin, contain caffeine - if you have a vascular headache, the caffeine will close down the blood vessels and relieve it.
With caffeine blocking the adenosine, you have increased neuron firing in the brain. The pituitary gland sees all of the activity and thinks some sort of emergency must be occurring, so it releases hormones that tell the adrenal glands to produce adrenaline (epinephrine). Adrenaline is, of course, the 'fight or flight' hormone and it has a number of effects on your body.