Coffee
From Chempedia
Coffee has been known as the "model drug of abuse" (Chemtech), and 3.4 cups daily are ingested by 56% of the population. Coffee is a necessary part of many peoples day because of its stimulant properties.
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Chemical properties:
The main component in coffee that acts as a stimulant is caffeine(C8H10N4O2), and caffeine is also known as trimethylxanthine (Daly, p.97, 1993). Caffeine is a member of a chemical group called xanthine, and xanthine, in the body, breaks down to form guanine and adenine which are two purine bases of DNA and RNA. (Daly, p.100). As caffeine enters the body, caffeine acts like the enzyme adenylyl cyclase. Adenylyl cyclase enzyme assist converting ATP to cyclic adenosine monophosphate (cAMP) to glucose by diffusing through the cytosol to help send out signals throughout the cells (Daly, p. 101). In addition, the caffeine structure is comparable to the adenine molecule. As caffeine and adenine compete for the adenosine binding sites of the cell, the competition of the two molecules allows no breaking down of cAMP so ATP does not convert to glucose (Daly, p.101). With the increase of cAMP, the body inhibits many chains of events.
Figure 1: Chemical Structure of Caffeine and Adenine
Caffeine ( Images provided by www.erowid.org/images/caffeine)
How does coffee act as a stimulant?
Caffeine works by stimulating the central nervous system. Caffeine is absorbed through the stomach and small intestine into the blood stream. Caffeine works on the molecular level by affecting adenosine receptors of nerve cells. The caffeine molecules bind to these receptors, which in turn block the attachment of adenosine to the cells, releasing adrenaline. When caffeine binds to the cells, it prevents adenosine from doing its job, which is slowing down nerve impulses and causing drowsiness. Caffeine works exactly opposite of adenosine by increasing heart rate, dilating pupils, and tightening the muscles. The amount of caffeine in the blood reaching the brain determines the severity of its effect on the body. The concentration of caffeine in the blood is at it maximal level within 15 to 45 minutes of caffeine consumption.
Effects of coffee’s stimulation:
Comparing the effects of coffee on an individual from many experiments is difficult due to the varying results. Many believe blood pressure is affected by the caffeine, and many results have shown otherwise (Jenkins). Some studies say there are negative health effects related to coffee, and some believe that coffee is the most significant source of anti-oxidants in the American diet (ACS). Moderate consumption of coffee very rarely is related to health problems, though high consumption can lead to anxiety, restlessness, insomnia, and tachycardia (an excessively rapid heartbeat). Although the stimulating effect of the caffeine attaching to nerve receptors and releasing adrenaline leaves you feeling energized and renewed, there becomes a tolerance to these effects. This tolerance has not been seen however in the cerebral energy metabolism, which is the speed of neuron firing in the brain. The cerebral energy metabolism is increased by caffeine ingestion in the ways explained above, and does not seem to develop a tolerance. So, while prolonged ingestion may lessen your feeling of awareness or energy levels, your brain is still going to be effected without change. This is particularly noticeable in the parts of the brain that are related to loco motor activity and areas of the brain relating to the sleep/wake cycle (Chemtech). As a result of the increased neuron firing in the brain from ingesting caffeine, the pituitary gland reacts. The pituitary gland is located at the base of the vertebrate brain. It secretes hormones that influence growth, metabolism, and maturation. The increased neuron firing from caffeine stimulates the pituitary gland to release hormones that make the adrenal glands produce adrenaline (Brain). Adrenaline effects one’s body by increasing blood pressure, dilating pupils, opening breathing tubes, making the heart beat faster, slowing blood flow to the stomach, and making the liver release sugar into the bloodstream for additional energy. Furthermore, blood vessels near the skin constrict to decrease blood flow from wounds and also to increase blood flow to muscles, and muscles tighten (Brain). Because of these effects, one feels excited, alert, and can maintain his or her concentration after drinking coffee; coffee also has the ability to help people recall short-term memory and increase IQ ("Coffee"). In addition, the stimulating properties of coffee affect the metabolism – making the body burn a higher amount of lipids to carbohydrates, which helps prevent muscles from fatiguing in active people. Like amphetamines and cocaine, caffeine is a stimulant, so it increases the amount of dopamine in the brain (Brain). Since dopamine stimulates the pleasure center of the brain, it would make sense why people feel good after drinking coffee. Although coffee is excellent for staying awake, the adrenaline that it makes one’s body release eventually wears off, potentially creating tiredness and depression (Brain). Because caffeine has a half-life of 6 hours (Brain), it stays in the body for a long period of time, which may prevent someone from getting a lot of deep sleep. This perpetuates fatigue and inspires people to drink more coffee.
Written by Sheng Herr, Navneet Agarwal, Brian Arnold, Ryan Foley, Deirdre Coleman, and Daisy Izevbigie
Works Cited:
Daly, John. Mechanism of Action of Caffeine; S, Garattini; Raven Press, Ltd., New York, 1993; pp. 97- 107.
Brain, Marshall. "How Caffeine Works." Howstuffworks; 1998. 21 Sept. 2005 http://science.howstuffworks.com/caffeine.htm/printable.
"Coffee." Wikipedia. 26 Sept. 2005. Wikimedia Foundation, Inc. 21 Sept. 2005 http://en.wikipedia.org/wiki/Coffee.
Paul Reisberg, "Caffeine", http://www.wellesley.edu, last modified: November 16, 1998.
www.en.wikipedia.org, "Caffeine", last modified: September 26, 2005.
Anne Marie Helmenstine, Ph.D., "Caffeine Chemistry", http://www.chemistry.about.com
Jenkins, Stephen H. How Science Works, Oxford University Press: Oxford, NY, 2004.
Chemtech. July 1999. Copyright: American Chemical Society; http://pubs.acs.org/hotartcl/chemtach/99/jul/negli.html accessed on 9/24/05
Http://acswwebapplications.acs.org/applications/ccs/application/index.cfm?pressreleaseid=2532&categor accessed on 9/24/05
www.erowid.org/images/caffeine accessed on 9/25/05
