Sanger used basic chemistry techniques and reactions, and took twelve years to complete his research. Today, automated instruments based on his approach can perform the same analysis in a matter of days. Sanger was awarded the Nobel Prize in Chemistry in for his insulin research.
Major contributions to health care have been made by chemistry. The development of new drugs involves chemical analysis and synthesis of new compounds. Many recent television programs advertise the large number of new drugs produced by chemists. The development of a new drug for any disease is long and complicated.
The chemistry of the disease must be studied, as well as how the drug affects the human body. A drug may work well in animals, but not in humans. Out of one hundred drugs that offer the possibility of treating disease, only a small handful actually turn out to be both safe and effective. Chemistry contributes to the preparation and use of materials for surgery sutures, artificial skin, and sterile materials. The sutures used in many surgeries today do not have to be removed, because they simply dissolve in the body after a period of time.
Replacement blood vessels for heart and other types of surgery are often made of chemicals that do not react with the tissues, so they will not be rejected by the body. Whether it is a small home garden or a large thousand acre farm, chemistry contributes greatly to the success of the crop. Crops need three things for good growth: water, nutrients from the soil, and protection from predators such as insects. Chemistry has made major contributions in all three areas.
Water purification uses a number of chemical and physical techniques to remove salts and contaminants that would pollute the soil.
Chemical analysis of soil allows the grower to see what nutrients are lacking so they can be added. In the spring, grocery stores, hardware stores, and gardening centers have high stacks of bags containing fertilizers and weed killers that enrich the soil and keep down unwanted plants.
These same stores also provide a number of sprays or solid treatments for insects that might otherwise have a snack on the plants. Fresh water is essential for good crops. In some areas of the world, there is enough rain to accomplish this task. In other locales, water must be provided so the crops will grow. A major source of cleaner water in many parts of the world is provided by the process of desalinization. Sea water is treated to remove salts and the resulting water can then be used for irrigation without contaminating the soil with materials that harm the growing plants.
In many areas of the world, the soil is deficient in essential nutrients. A number of minerals such as phosphorus, potassium, calcium, and magnesium may not be present in large enough amounts to cause good plant growth. Nitrogen is extremely important for good crops. Soil analysis is available from a variety of labs. Local university extension services can provide valuable information as to the composition of a soil and will also make suggestions as to the types and amounts of needed nutrients.
Fertilizers can be purchased and added to the soil to enrich it and ensure better yield of crops. Even if the crop grows well, there is still the possibility of insect or pest damage.
The insect or pest can consume the crop or can damage it to the point where it will not grow well. Infestations of armyworms can do major damage to corn and grain crops. Aphids and boll weevils are major predators of cotton crops. Failure to control these pests will result in widespread crop damage and financial loss to the farmer. A wide variety of pesticides have been developed by chemists and other scientists to deal with all these pests.
The basic approach is to have the pesticide interfere with some biochemical process in the pest. Ideally, the pesticide will not affect other living organisms, but this is not always the case. It is very important to read the labels and observe all precautions when using pesticides.
Chemistry research is often full of surprises. One such surprise came to Stephanie Kwolek of the DuPont chemical company. She was working on a type of material known as polymers. These chemicals had been around for a while and were being used for new types of textiles. Kwolek was looking for a strong and rigid petroleum product. She came up with a material that did not look like your average polymer.
But she played a hunch and had it made into threads. This new material had stiffness about nine times that of any of the known polymers of the time. Further research and development led to the production of Kevlar, a material now widely used in body armor see figure above.
In addition, Kevlar has found wide application in racing sails, car tires, brakes, and fire-resistant clothing worn by firefighters. Chemists are involved in the design and production of new materials. Some of the materials that chemists have helped discover or develop in recent years include polymers, ceramics, adhesives, coatings, and liquid crystals. Liquid crystals are used in electronic displays, as in watches and calculators. The silicon-based computer chip has revolutionized modern society and chemists have played a key role in their design and continued improvement.
The calculator shown below uses both a liquid crystal display and chips inside the device. Many chemists are currently working in the field of superconductivity. The challenge is to design materials that can act as superconductors at normal temperatures, as opposed to only being able to superconduct at very low temperatures.
The fibers that compose the materials for our clothes are either natural or human-made. Silk and cotton would be examples of natural fibers. Silk is produced by the silkworm and cotton is grown as a plant.
Human-made fabrics include nylon, orlon, and a number of other polymers. These materials are made from hydrocarbons found in petroleum products.
Synthetic polymers are also used in shoes, raingear, and camping items. The synthetic fabrics tend to be lighter than the natural ones and can be treated to make them more water-resistant and durable. Materials originally developed as textiles are finding a wide variety of other uses. Nylon is found in a number of plastic utensils.
Many drugs that act in the brain are able to do so because they are relatively non-polar and can cross from the blood into the brain simply by diffusion. The main active ingredient of cannabis, deltatetrahydrocannabinol THC , is one such molecule. Figure 1 shows the structure of THC with only two areas of polarity the two oxygen atoms within a long hydrocarbon. The non-polar nature of THC means that it is poorly soluble in water and hence in blood.
When THC is administered, it quickly moves out of the blood into fatty tissue. This explains the low correlation between the blood levels of cannabis and the degree of biological effect. Figure 1 - THC and lignocaine; the non-polar structure of THC left explains its low solubility in the bloodstream; lignocaine right is a weak base and is protonated in low pH. On occasion, medicinal chemists may need to prevent a drug from crossing into the brain to reduce unwanted side effects.
One example of this is seen with antihistamine drugs. Older antihistamines cause drowsiness because they are able to cross into the brain. When newer versions were developed, functional groups — like carboxylic acids — were introduced to make the drug more hydrophilic and prevent it crossing into the brain.
So the ethanol concentration in exhaled air reflects its concentration in the blood, and this in turn reflects its concentration at the site of action in the brain. Many drugs are either weak acids or weak bases, so the extent to which they are charged depends on the pH. When given in tablet form most drugs are absorbed in the small intestine, which has a pH between 6 and 7.
The majority of drugs are weak bases and are likely to be absorbed more easily as they reach the more alkaline part of the small intestine. Blood pH is generally maintained at around 7. In generalised inflammation, as occurs in sepsis, the body pH can fall from 7. This may seem like quite a small change in pH, but it means a very large change in the ionisation of a weak base. At the heart of cellular respiration are oxidation—reduction reactions that generate heat from the chemical energy store in foods such as glucose.
Dehydrogenase enzymes remove two electrons and two protons from the substrate, in this case glucose.
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