Lactose Intolerance

Lactose, also known as milk sugar, is the major carbohydrate found in milk. Its sweetness is 16% that of sucrose (table sugar). The lactose content of mother's milk obtained by nursing infants [7-8% (m/m)] is almost twice that in cow's milk [4-5% (m/m)]. Lactose supplies about 40% of the energy in human milk.

Many adults lack the enzyme lactase, necessary for the digestion of lactose; this causes lactose intolerance. When lactose molecules remain in the intestine undigestded, they attract water to themselves, causing fullness, discomport, cramping, nausea, and diarrhea. The level of lactase in humans varies with age. Most people have sufficient lactase during childhood years when milk is a needed calcium source. In adulthood, lactase levels decrease and lactose intolerance develops. This explains changes in milk-drinking habits of many adults. About one-third of Americans suffer from lactose intolerance.

The level of the enzyme lactase in humans varies widely among ethnic groups, indicating tht the trait is genetically determined (inherited). The occurence of lactose intolerance is lowest among Scandinavians and other nothern Europeans and highest among native Americans, Southeast Asians, Africans, and Greeks.

[Source: Chemical Principles by H. Stephen Stoker]

Hydrogen Sulfide

The hydrogen sulfide molecule is the sulfur analog of water, witha central sulful atom in place of the central oxygen atom.

Hydrogen sulfide is a gas at room temperature with an odor that resembles rotten eggs. Natural sources of it include bacterial decomposition of proteins and volcanic eruptions.

Nasal detection of hydrogen sulfide is possible at concentration as low as 0.02 part per million. Despite its easy detection, its presence can be dangerous because it exerts an anesthetic effects on nasal passages, causing the nose to rapidly lose its ability to detect its presence. Hydrogen sulfide is lethal at a concentration of 100 parts per million.

Decomposition of albumin, a sulfur-rich protein present in eggs, produces hydrogen sulfide. The pale green color often found at the interface of the yolk and white portion of a cooked egg is caused by the presence of hydrogen sulfide. Egg yolk is rich in iron-containing proteins, and H2S produced from albumin during cooking reacts with these proteins to form iron sulfide, the source of the green color.

[source: Chemical Principles by H. Stephen Stoker]

AirBag

An increasing number of automobiles are equipped with airbags that rapidly inflate on collision, before car occupants can be thrown forward after impact. The chemistry principle involved in the inflation process involves a controlled chemical explosion that produces a large volume of gas (which inflates the bag).

Nitrogen gas (N2) is the inflatant in most airbags. Airbags are activated when an impact causes a steel ball to compress a spring and electrically ignite a detonator cap, which in turn, causes sodium azide (NaN3) to decompose, forming nitrogen gas and metallic sodium. (100g of NaN3 produces 56L of Ns gas at 25 celsius.) The sodium metal produced, an undesirable decomposition product because of its reactivity, instantaneously reacts with iron(III) oxide, which is included in the reaction container, to produce sodium oxide (Na2O) and Iron (Fe).

[Source: H. Stephen Stoker, Chemical Principles]

Alkaloids

Caffeine, as well as nicotine, are examples of compounds that are called alkaloids. Alkaloids are physiologically active compounds produced by plants.

People in various parts of the world have known for centuries that physiological effects can be obtained by eating or chewing the leaves, roots, or bark of certain plants. Over 5000 different compounds that are physiologically active have been isolated from such plants.

Besides caffeine(coffee beans and tea leaves) and necotine(tobacco leaves), other alkaloids include cocaine (coca plant) atropine, and opium. The latter three alkaloids are currently used in medicine.

Quinine, which occurs in cinchoha bark, is used to treat malaria. Atropine, which is isolated from the bellodonna plant, is used to dilate the pupil of the eye in patients undergoing eye examination. Opium, the dried juice of the oriental poppy plant, has been used for centuries as a pain-killing drug. It contains numerous alkaloids, including morphine and codeine.

Ethylene

Ethylene, a colorless, flammable gas with a slightly sweet odor, is both a natural product and an important industrial chemical. Its molecular formula is C2H2.

Ethylene occurs naturally in small amounts in plants where it functions as a plant hormone. Many fruits and vegetables, especially citrus fruit and tomatoes, release ethylene as they ripen. The released ethylene triggers futher ripening.

The commercial fruit industry uses to advantage this ripening function for ethylene. Crops, such as bananas and tomatoes, are picked green to prevent spoiling and bruising during transportation to markets. At its destination, the fruit is exposed to ethylene gas, which stimulates the ripening process; 1kg of tomatoes can be ripened by exposure to 0.1 mg of ethylene.

Industrially, U.S. chemical manufacturers produce more ethylene each year than any other compound except sulfuric acid. The ethylene does not reach consumers directly; most of it goes into the production of plastics and synthetic fibers. Almost half of the ethylene produced is consumed in the production of the well-known plastic called polyethylene.

[source: Chemical Principles by H. Stephen Stoker]

Epinephrine

Adrenaline, also known as epinephrine, has the chemical formula C9H13O3N. It is a hormone released from the adrenal glands into the bloodstream, usually in response to pain, excitement, anger, or fear, that increases the level of glucose in the blood. The extra glucose, a key source of energy for body processes, in turn increases rate and force of heart contraction, muscular strength, and blood pressure. These changes cause the body to function at a "higher" level. For this reason, adrenaline is often called the "fight or flight" hormone.

Adrenaline-caused increase blood pressure results from increased heart action accompanied by constriction of peripheral blood vessels. Injectable local anesthetics usually contain adrenaline because it constricts blood vessels in the vicinity of the injection. This prevents the blood from rapidly distributing the anesthetic and prolongs the anesthetic effect in the target tissue. Andrenaline is also used to reduce hemorrahage.

[source: Chemical Principles by H. Stephen Stoker]

Acetaminophen

Acetaminophen has replaced aspirin as the most widely used of all nonprescription pain relievers. Its use now accounts for over half of the over-the-counter pain reliever market. It is marketed generally and under trade names such as Tylenol, Datril, Tempra, and Anacin-3. Acetaminophen's availability in a liquid form makes it an ideal medication for small children and other patients who have difficulty taking solid tablets.

Acetaminophen , often called the "Aspirin substitute," has no irritationg effect on intestinal tracts as does aspirin and yet has comparable pain-relieving effect and fever-reducing effects. However, it is not effective against inflammation as is aspirin and is thus of limited use for the aches and pains of arthritis. Also, acetaminophen does not have any blood thinning properties, as does aspirin, and therefore is not useful as an aid in reducing the risk of stroke and heart attack.

[source: Chemical Principles by H. Stephen Stoker]