Chemistry around us

Chemical reactions influence the stuff around us and there are numerous instances where chemicals and chemistry helps us live a better life. The cooking of food, the clothes we wear, fertilizers that we use for crops, cement used for building our houses, the power plants that generate electricity, and many other processes depend on chemistry. The human dependence on this natural science is increasing and to understand this, here are a few examples that highlight the importance of chemistry around us.

1. Photosynthesis. Photosynthesis involves energy transformation and is a chemical process wherein plants, algae and some bacteria produce their own food. It is the synthesis of glucose using carbon dioxide and water in presence of sunlight trapped by chlorophyll present in the leaves. The reaction which occurs is depicted as: 6CO₂ + 6H₂O + Light Energy = C₆H₁₂O₆ + 6O₂. Photosynthesis is the reverse process of respiration. They both are inter-dependent. We get an uninterrupted supply of oxygen, and plants get the carbon dioxide they need. Thus, photosynthesis plays a significant role in our day-to-day life.

2. Color of Meat. There are two types of meat: red and white. Red meat contains a highly pigmented protein called myoglobin that stores oxygen in the muscle cells. More the myoglobin in the cells, the redder is the meat. However, as meat is heated, the proteins break down and shrink in size. When the interior of the meat reaches 170° F, hemichrome (a tan colored compound) levels rise, and the myoglobin becomes metmyoglobin, which gives well-done meat its brown-gray shade. White meat contains glycogen, which has a translucent " glassy" quality when it is raw. When it's cooked, the proteins recombine, or coagulate, and the meat becomes opaque and whitish.

3. Apples Turning Brown. Apples contain an enzyme called polyphenol oxidase (PPO), also known as tyrosinase. Cutting an apple exposes its cells to the atmospheric oxygen and oxidizes the phenolic compounds present in apples. This is called the enzymatic browning that turns a cut apple brown. In addition to apples, enzymatic browning is also evident in bananas, pears, avocados and even potatoes.

4. Crying and Onions. When you cut an onion you break the cells that form the layers in an onion, thus releasing an enzyme alliinase that reacts with a sulfur-containing compound known as 'prensco', which is also released while cutting. This reaction results in the formation of 1-propenyl sulfenic acid. This acid is further converted to propanethiol S-oxide, a volatile sulfur compound, by the enzyme LF-synthase (meaning lachrymatory factor synthesizing enzyme). This gas, known as the lachrymatory factor (crying factor), reacts with the water in our eyes to form sulfuric acid causing a burning sensation in your eyes and indicating the tear gland to secrete tears.

5. Stain Removers. Soap is formed by the reaction between an alkali and a fatty acid. This produces a molecule with one hydrophilic (water-loving) and one lipophilic (fat-loving) ends. The lipophilic ends stick to oil, grease or dirt. These get engulfed in the soap and are washed away with a fresh stream of water, leaving a clean surface behind. This is just a physical reaction that takes place. Soap and stain removers act as emulsifiers which allow oil and water to mix and so the oily mixtures and difficult stains on body and clothes can be removed after application of soap, stain removers and water.

6. Ripening of Fruits. A simple hydrocarbon gas ethylene switches on the necessary genes that stimulate the secretion of the ripening enzymes which catalyze reactions to change the properties of the fruit. Ethylene channelizes the action of several other chemicals called hydrolase, amylase, kinase and pectinase. These enzymes convert starch to sugar, alter the cell walls to make them softer, neutralize acids and cause the fruit to emit an aroma.
7. Fermentation. Fermentation is the conversion of complex substances to simpler ones under anaerobic conditions. The specific product from fermentation is driven by the type of micro-organisms acting on the substance in which the fermentation occurs. The products of fermentation are alcohols or acids and the release of carbon dioxide. For example, wine produced from fruit juice is an alcohol as a result of fermentation by yeast, whereas beer is the result of yeast fermentation of grain. Antibiotics are obtained through fermentation by molds and some bacteria. Yogurt, cheese and vinegar are products of bacterial fermentation. Leavened bread is obtained by yeast fermentation.

8. Sunscreens. Sunscreens are a combination of organic and inorganic compounds. Inorganic chemicals like titanium dioxide or zinc oxide form a physical barrier that reflects or scatters UV waves. Organic components like octyl methoxycinnamate (OMC) or oxybenzone absorb UV rays and release their energy as heat. This protects our skin from sunburns and detrimental effects like cancer.

9. Nail Paint Removers. Nail paint consists of three types of ingredients which are organic solvents and drying agents, thickeners and hardening agents along with coloring agents. The remover is actually an organic solvent that is used as an ingredient in nail paint which may be acetone or ethyl acetate. So when you apply the remover you are just bringing it back to its original state. The solvent molecules get in between the chains of polymers and separate them, making it easy to wipe it off with a ball of cotton.

10. Static Shocks. All materials are made up of electrical charges in the atoms of the material. There are equal quantities of electrons (negative charges) and protons (positive charges) that try to balance each other in the universe. Friction between two materials causes these charges to redistribute. The electrons from one atom are transferred to the other. As we know, like charges repel each other and unlike charges attract each other. Whenever you touch anything that is a good conductor of electricity, the transfer of the extra electrons that have accumulated takes place, and it gives you the static shock. For example, generally in winters, you get a shock when you get out of the car or when you touch the door knob or filing cabinet.

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