introduction about diffrent types of polymers
- 1. Laboratory-1 Subject: Rubber Technology (3132602) Date: 01/07/2020 AIM: To study about Natural Polymers. Savani Parth-19028126030
- 2. 1.Natural rubber How is Natural Rubber Made? The raw material from which natural rubber is made comes from the sap of rubber trees. The rubber plants are tapped for collecting the rubber latex. For this, an incision is made into the bark of the rubber tree and the latex sap is collected in cups. After collecting the latex sap, the raw natural rubber is refined to convert it into a usable rubber. Initially an acid was added to the latex which used to make the sap set like a jelly. The latex jelly thus obtained was then flattened and rolled into rubber sheets and hung out to dry. In the year 1839, Charles Goodyear invented a more sophisticated way of making rubber stronger and more elastic. This was the process of rubber vulcanising. The unprocessed natural rubber is sticky, deforms easily when warm, and is brittle when cold. In such a state, it cannot be used to make products having a good level of elasticity. Vulcanization prevents the polymer chains from moving independently. As a result, when stress is applied the vulcanized rubber deforms, but upon release of the stress, the product reverts to its original shape. Source of Natural Rubber The natural rubber is produced from hundreds of different plant species. However, the most important source is from a tropical tree known as Hevea brasiliensis, which is native to the tropical Americas. This tree grows best in areas with an annual rainfall of just under 2000mm and at temperatures of 21-28 degrees.
- 3. Due to these features and the preferred altitude of the tree around 600 metres, the prime growing area is around 10 degrees on either side of the equator. However it is also cultivated further north in China, Mexico, and Guatemala. Properties of Natural Rubber Natural rubber combines high strength (tensile and tear) with outstanding resistance to fatigue. It has excellent green strength and tack which means that it has the ability to stick to itself and to other materials which makes it easier to fabricate. It has moderate resistance to environmental damage by heat, light and ozone which is one of its drawback. The natural rubber has excellent adhesion to brass-plated steel cord, which is ideal in rubber tyres. It has low hysteresis which leads to low heat generation, and this in turn maintains new tyre service integrity and extends retreadability. The natural rubber has low rolling resistance with enhanced fuel economy. It has high resistance to cutting, chipping and tearing.
- 4. Uses of Natural rubber Natural rubber forms an excellent barrier to water. This is possibly the best barrier against pathogens such as the AIDS virus (HIV). That is the reason why latex is used in in condoms and surgical and medical examination gloves. Natural rubber is an excellent spring material. Natural rubber latex is also used in catheters, balloons, medical tubes, elastic thread, and also in some adhesives. Other than rayon, it is the sole raw material, which is used by the automotive industry. Rubberwood is another byproduct of natural rubber which is growing in importance. It is a source of charcoal for local cooking.
- 5. 2. Lignin Lignin, the second most abundant biopolymer on the planet, serves land- plants as bonding agent in juvenile cell tissues and as stiffening (modulus-building) agent in mature cell walls. The chemical structure analysis of cell wall lignins from two partially delignified wood species representing between 6 and 65% of total wood lignin has revealed that cell wall-bound lignins are virtually invariable in terms of inter-unit linkages, and resemble the native state. Variability is recognized as the result of isolation procedure. In native state, lignin has a low glass-to- rubber transition temperature and is part of a block copolymer with non- crystalline polysaccharides. This molecular architecture determines all of lignin's properties, foremost of all its failure to undergo interfacial failure by separation from (semi-) crystalline cellulose under a wide range of environmental conditions. This seemingly unexpected compatibility (on the nano-level) between a carbohydrate component and the highly aromatic lignin represents a lesson by nature that human technology is only now beginning to mimic. Since the isolation of lignin from lignocellulosic biomass (i.e., by pulping or biorefining) necessitates significant molecular alteration of lignin, isolated lignins are highly variable in structure and reflect the isolation method. While numerous procedures exist for converting isolated (carbon-rich) lignins into well-defined commodity chemicals by various liquefaction techniques (such as pyrolysis, hydrogenolysis, etc.)
- 6. The use of lignin in man-made thermosetting and thermoplastic structural materials appears to offer greatest value. The well-recognized variabilities of isolated lignins can in large part be remedied by targeted chemical modification, and by adopting nature's principles of functionalization leading to inter-molecular compatibility. Lignins isolated from large-scale industrial delignification processes operating under invariable isolation conditions produce polymers of virtually invariable character. This makes lignin from pulp mills a potentially valuable biopolymeric resource. The restoration of molecular character resembling that in native plants is illustrated in this review via the demonstrated (and in part commercially-implemented) use of pulp lignins in bio-degradable (or compostable) polymeric materials.
- 7. 3.Humus A fallen tree decays in a cypress swamp. The tree will continue to decay until it decomposes entirely, becoming part of the humus in the swamp bed. Humus is dark, organic material that forms in soil when plant and animal matter decays. When plants drop leaves, twigs, and other material to the ground, it piles up. This material is called leaf litter. When animals die, their remains add to the litter. Over time, all this litter decomposes. This means it decays, or breaks down, into its most basic chemical elements. Many of these chemicals are important nutrients for the soil and organisms that depend on soil for life, such as plants. The thick brown or black substance that remains after most of the organic litter has decomposed is called humus. Earthworms often help mix humus with minerals in the soil. Humus contains many useful nutrients for healthy soil. One of the most
- 8. important is nitrogen. Nitrogen is a key nutrient for most plants. Agriculture depends on nitrogen and other nutrients found in humus. Some experts think humus makes soil more fertile. Others say humus helps prevent disease in plants and food crops. When humus is in soil, the soil will crumble. Air and water move easily through the loose soil, and oxygen can reach the roots of plants. Humus can be produced naturally or through a process called composting. When people compost, they collect decaying organic material, such as food and garden scraps, that will be turned into soil. Compost, like humus, is made of decomposed organic material. Compost usually refers to material created by people from leftover foods and yard waste. Humus usually refers to the natural decay of material such as leaves in the soil's top layer
- 9. 4.Coal Coal is a fossil fuel and is the altered remains of prehistoric vegetation that originally accumulated in swamps and peat bogs. The energy we get from coal today comes from the energy that plants absorbed from the sun millions of years ago. Coal formation All living plants store solar energy through a process known as photosynthesis. When plants die, this energy is usually released as the plants decay. Under conditions favourable to coal formation, the decaying process is interrupted, preventing the release of the stored solar energy. The energy is locked into the coal. Coal formation began during the Carboniferous Period - known as the first coal age - which spanned 360 million to 290 million years ago. The build-up of silt and other sediments, together with movements in the earth's crust - known as tectonic movements - buried swamps and peat bogs, often to great depths. With burial, the plant material was
- 10. subjected to high temperatures and pressures. This caused physical and chemical changes in the vegetation, transforming it into peat and then into coal. Coalification The degree of change undergone by a coal as it matures from peat to anthracite is known as coalification. Coalification has an important bearing on coal's physical and chemical properties and is referred to as the 'rank' of the coal. Ranking is determined by the degree of transformation of the original plant material to carbon. The ranks of coals, from those with the least carbon to those with the most carbon, are lignite, sub-bituminous, bituminous and anthracite.
- 11. 5.Kerogen Kerogen is a waxy, insoluble organic substance that forms when organic shale is buried under several layers of sediment and is heated. If this kerogen is continually heated, it leads to the slow release of fossil fuels such as oil and natural gas, and also the non-fuel carbon compound graphite. Shales that are especially rich in kerogen can actually be burned directly, but only have seen limited use as a fuel throughout history. During petroleum generation, bitumen also forms from kerogen. There are different types or classes of kerogen. Type I consists mainly of algae and is the most likely type of kerogen to produce oil when exposed to high temperatures. Type II is a type of kerogen that is composed of a mix of terrestrial and marine organic materials and can sometimes produce oil. Type III kerogen is composed mainly of wood- like material along with some algae and plankton, generally creating natural gas. Kerogen is considered to be a major carbon sink in the carbon cycle, containing nearly 1016 tonnes of carbon. As well, the ability to study kerogen has led to insight in the formation of sedimentary rocks and how these organic materials are incorporated into these rocks.
- 12. Formation The formation of kerogen represents a major step in the formation of oil and natural gas, as kerogen serves as the source of these fossil fuels. For kerogen to form, dead phytoplankon, zooplankton, algae, and bacteria must sink to the bottom of an ancient still water environment. After, this dead material must mix with inorganic, clay-like materials that enter these oceans from streams and rivers. This creates an organic-rich mud - which cannot be exposed to too much oxygen or else the organic matter within the mud is decomposed too quickly by bacteria. Before this organic matter is destroyed, it is buried by more sediment and lithifies (becomes sedimentary rock), creating organic shale. If this shale is buried between 2 and 4 kilometers, its temperature increases due to its location in the Earths interior. This increasing pressure and temperature of the shale finally transforms it into kerogen.
- 13. 6.Asphaltenes (Bitumen) What Is Bitumen? Bitumen, also known as asphalt in the United States, is a substance that forms through the distillation of crude oil. It has waterproofing and adhesive properties. Bitumen production through distillation removes lighter crude oil components, such as gasoline and diesel, leaving the ―heavier‖ bitumen behind. The producer often refines it several times to improve its grade. Bitumen can also occur in nature: Deposits of naturally occurring bitumen form at the bottom of ancient lakes, where prehistoric organisms have since decayed and have been subjected to heat and pressure.
- 14. Understanding Bitumen Bitumen is generally for industry use. Bitumen was first used for its natural adhesive and waterproofing characteristics, but it was also used as a medicine. It was used to bind building materials together, as well as to line the bottoms of ships. Ancient civilizations traded the material. Herodotus, a fifth-century BC Greek historian, claimed that the walls of ancient Babylon contained bitumen. Bitumen is composed of complex hydrocarbons and contains elements such as calcium, iron, sulfur, and oxygen. The quality of material and ease of production depends on the source and type of crude oil it is derived from. The material is used most often in road paving. Most roads in the United States are made of either bitumen or a combination of bitumen and aggregates, such as concrete. Engineers replacing asphalt roads can reuse the material on other road projects. Manufacturers use it in the creation of roofing products due to its waterproofing qualities. Under heavy loads, bitumen can deform permanently, depending on the composition of the asphalt mixture, the ambient temperature, and the amount of stress places on the material. Bitumen oxidizes, which can leave the asphalt brittle and result in it cracking. Naturally Occurring Bitumen Bitumen is also a term used to refer to oil sands, or partially consolidated sandstone containing a naturally occurring mixture of sand, clay, and water, saturated with a dense and extremely viscous form of petroleum. Bituminous sands are extremely abundant in Canada, especially in the province of Alberta, where rising oil prices have made it economical to extract petroleum from these sands on a large scale. The
- 15. Canadian Energy Research Institute estimates that the price of crude oil must hit $70.08 per barrel for a stand-alone bitumen mine to be profitable.
- 16. 7.Shellac Shellac is a natural resin of outstanding properties and exceptional versatility. The only known commercial resin of animal origin, it is hardened secretion of a tiny insect, Laccifer lacca (Kerr), popularly known as the lac insect. Lac being a natural organic resin having biodegradable properties is one of the many gifts of nature given to mankind. It has been in use for centuries in some form or other. Lately the scientific community has observed the significance of Lac resins. Sticklac (Raw Lac or Raw Shellac) Lac crop is collected by cutting down the lac bearing twigs of the hosts either weeks before larval emergence, when it is known as ari, or after, when it is known as phunki. Lac encrustations are separated from the twigs by either breaking off by hand or scrapping with a knife or sickle. Lac, thus gathered, is known as sticklac and it is in this form that
- 17. cultivators bring it to the market for sale to manufacturers or their agents. Properties of Shellac Shellac, edible, is a hard amorphous natural resin & considered GRAS (Generally Recognized As Safe) by the FDA (Food and Drug Administration). Lac was employed as a dye in cosmetics and as as constituent of medicines for centuries. To-day lac is being used in many industries as a film former, a plastic, an insulator and an adhesive and cement. Shellac is used in Electrical equipments because of its excellent dielectric properties, dielectric strength, low thermal conductivity and a low coefficient of expansion. Shellac coatings do not change their electrical properties under UV-radiation. Because of its acidic properties (resisting stomach acids), shellac-coated pills may be used for a timed enteric or colonic release. Shellac is used as a 'wax' coating on citrus fruit to prolong its shelf/storage life. It is also used to replace the natural wax of the apple, which is removed during the cleaning process. It is the central element of the traditional method of finishing furniture and fine violas, guitars and pianos. Because it is compatible with most other finishes, shellac is also used as a barrier or primer coat on wood to prevent the bleeding of resin or pigments into the final finish, or to prevent wood stain from blotching. Shellac is an odour and stain blocker and so is often used as the base of "solves all problems" primers. Shellac provides an excellent barrier against water vapour penetration. Shellac- based primers are an effective sealant to control odours associated with fire damage.
- 18. Uses of Shellac The largest uses for shellac are for the food, drug, and cosmetics industries. Fruits and vegetables in the produce aisle of your favorite grocery store are coated with shellac and wax to make them shiny and eye-catching. In the world of cosmetics, women and men use shellac- based hair-spray to make themselves appear shiny and more eye- catching. Many vitamins, pills and food supplements are coated with shellac to make them slide easily down your throat, into your tummy. As a film former : In french polishes, metal foil and pear varnishes, undercoats, enamels and wood sealers. In the cosmetic industry, shellac is known as a "Nail treatment" that lasts longer than regular polish. It is a combination of gel and regular polish and offers a water resistant seal among nail protection. As glaze for confectionery, coffee beans and medicinal pills. As aqueous varnishes for leather dressing, wood and paper and floor polishes, etc. As a dye for cotton and, especially, silk cloth. In watchmaking, due to its low melting temperature (about 80-100 °C), to adjust and adhere pallet stones to the pallet fork. In dental technology, where it is occasionally used in the production of custom impression trays and (partial) denture production. As a Ink : Applications such as lithographic ink, waterproof ink and colored ink. To increase the strength and longevity of ballet pointe shoes as a remedy for moisture weakening. In fireworks pyrotechnic compositions as a low-temperature fuel, where it allows the creation of pure 'greens' and 'blues'- colours difficult to achieve with other fuel mixes. As a plastic : In gramophone records, grinding wheels, sealing waxes, general moulded articles, insulators etc.
- 19. As an insulator : In insulating varnishes, laminated paper products, micanites and micafolium, insulating cloth etc. As an adhesive and cement : In laminated paper and jute boards, plate sealer, gasket cement, general cements, optical cement, caping cement for electrical lamps and radio values, abrasive paper and cloth etc. As a Polish & Paints : Owing to the light color of bleached lac, bleached lac polishes are chiefly used for finishing wooden floors, playing cards, sports goods, ivory articles etc. As protective coatings : In confectionery and medicinal pills. As stiffening agents for felt and fabric hats : constituent of gossamer (or goss for short), a cheesecloth fabric coated in shellac and ammonia solution used in the shell of traditional silk top and riding hats. For preserving and imparting a shine to citrus fruits, such as lemons etc. In Jelly Belly jelly beans, in combination with beeswax to give them their final buff and polish. As a binder in Printing ink. As a protective and decorative coating for handlebar tape in cycle , and as a hard-drying adhesive for tubular cycle tires, particularly for track racing. For reattaching ink sacs when restoring fountain pens. For mounting insects As a binder in the fabrication of abrasive wheels, imparting flexibility and smoothness not found in vitrified (ceramic bond) wheels. Areas of Cultivation India contributes the largest share of world’s production of lac. Other countries producing lac are Thailand, Burma, Sri Lanka and Pakistan, Of these, the last three countries do no produce appreciable amounts. Thailand , however, has developed her lac industry considerably since World War II. In India, the chief areas of lac cultivation are the districts of Chhattisgarh, adjacent districts of Madhya Pradesh, plateau of Bihar, West Bengal, Orissa and Assam. Limited quantity are also produced in Uttar Pradesh, East Punjab, Mysore and Madras.
- 20. 8.Amber Amber is probably best known for its insect and other types of inclusions. Millions of years ago, when amber oozed from countless plants, the substance acted as a sticky trap for ants, bees, termites, and other insects. Flower parts, leaves, and pine needles are also typical amber inclusions, along with gas bubbles. Amber containing larger animals like scorpions, snails, frogs, and lizards can be very valuable—especially if the animal ―inclusions‖ are preserved intact. Fossilized Extinct Lizard The fossilized extinct lizard trapped in this piece of amber from the Dominican Republic is over a million years old. Insects embedded in amber formed the basis of the movie ―Jurassic Park.‖ The story centered around the cloning of dinosaurs from DNA
- 21. found in dinosaur blood sucked up by prehistoric mosquitoes that were subsequently preserved in amber. The movie generated great interest in the gem. Amber is an organic gem. Organic gems are the products of living or once-living organisms and biological processes. Amber formed tens of millions of years ago, when sap from ancient trees hardened and fossilized. Amber in a Variety of Colors Amber comes in a variety of colors. The most familiar ones are yellow to orange, while a reddish color is rare. This group includes cloudy amber, reddish amber from Myanmar, amber with stress fractures, and pale, almost opaque, amber.
- 22. Scientists and collectors treasure amber that contains suspended animal or plant fragments. These fossilized bits of once-living things were trapped in the hardening amber, creating a fascinating time capsule. Some types of amber are found in the ground. Other types have been freed and carried by tides, ending up on beaches or near-shore areas. The Baltic coast bordering Germany, Poland, and Russia is still an important source of amber. Gas Bubbles in Amber Gas bubbles are very common amber inclusions. If there are a lot of them, they can give the material a cloudy appearance. Amber is sometimes called ―gold of the North.‖ Its warm luster is featured in beads, carvings, pendants, and cabochons, as well as decorative items like cups, bowls, snuff boxes, and umbrella handles. A related material, called copal, is also fossilized tree resin, but it’s far younger than amber, at less than a million years old.
- 23. Copal Like amber, copal is fossilized tree resin, but it is not as old. Amber must be over a million years old, while copal is younger—often around a hundred thousand years old.
- 24. 9.Cellulose Cellulose is a substance found in the cell walls of plants. Although cellulose is not a component of the human body, it is nevertheless the most abundant organic macromolecule on Earth. The scientific community first observed cellulose in 1833 when it was studied in plant cell walls. The chemical structure of cellulose resembles that of starch, but unlike starch, cellulose is extremely rigid .This rigidity imparts great strength to the plant body and protection to the interiors of plant cells. Structure Of Cellulose Cellulose, a linear polymer of D-glucose units (two are shown) linked by β(1→4)-glycosidic bonds. Like starch, cellulose is composed of a long chain of at least 500 glucose molecules. Cellulose is, thus, a polysaccharide (Latin for ―many sugars‖). Several of these polysaccharide chains are arranged in parallel arrays to form cellulose microfibrils. The individual polysaccharide chains are bound together in the microfibrils by
- 25. hydrogen bonds. The microfibrils, in turn, are bundled together to form macrofibrils . The microfibrils of cellulose are extremely tough and inflexible due to the presence of hydrogen bonds. In fact, when describing the structure of cellulose microfibrils, chemists call their arrangement crystalline, meaning that the microfibrils have crystal-like properties. Although starch has the same basic structure as cellulose—it is also a polysaccharide—the glucose subunits are bonded in such a way that allows the starch molecule to twist. In other words, the starch molecule is flexible, while the cellulose molecule is rigid. How Cellulose Is Arranged In Plant Cell Walls Like human bone, plant cell walls are composed of fibrils laid down in a matrix, or background material. In a cell wall, the fibrils are cellulose microfibrils, and the matrix is composed of other polysaccharides and proteins. One of these matrix polysaccharides in cell walls is pectin, a substance that, when heated, forms a gel. Pectin is the substance that cooks use to make jellies and jams. The arrangement of cellulose microfibrils within the polysaccharide and protein matrix imparts great strength to plant cell walls. The cell wall of plants performs several functions, each related to the rigidity of the cell wall. It protects the interior of the plant cell, but also allows the circulation of fluids within and around the cell wall. The cell wall also binds the plant cell to its neighbors. This binding creates the tough, rigid skeleton of the plant body. Cell walls are the reason why plants are erect and rigid. Some plants have a secondary cell wall laid over the primary cell wall. The secondary cell wall is composed of yet another polysaccharide called lignin. For example, lignin is found in
- 26. trees. The presence of both primary and secondary cell walls makes the tree even more rigid, penetrable only with sharp axes. As the plant cell grows, it must expand to accommodate the growing cell volume. However, because cellulose is so rigid, it cannot stretch or flex to allow this growth. Instead, the microfibrils of cellulose slide past each other or separate from adjacent microfibrils. In this way, the cellwall is able to expand when the cell volume enlarges during growth. Cellulose Digestion Humans lack the enzyme necessary to digest cellulose. Hay and grasses are particularly abundant in cellulose, and both are indigestible by humans (although humans can digest starch). Animals such as termites and herbivores such as cows, koalas, and horses all digest cellulose, but even these animals do not themselves have an enzyme that digests this material. Instead, these animals harbor microbes that can digest cellulose. The termite, for instance, contains protists (single-celled organisms) called mastigophorans in their guts that carry out cellulose digestion. The species of mastigophorans that performs this service for termites is called Trichonympha, which, interestingly, can cause a serious parasitic infection in humans.
- 27. 10.Starch Starch or amylum is a polymeric carbohydrate consisting of numerous glucose units joined by glycosidic bonds. This polysaccharide is produced by most green plants as energy storage. It is the most common carbohydrate in human diets and is contained in large amounts in staple foods like potatoes, maize (corn), rice, and cassava, as well as in the grain Emmer wheat (Triticum amyleum), from which is produced a cultivated white starch. Pure starch is a white, tasteless and odorless powder that is insoluble in cold water or alcohol. It consists of two types of molecules: the linear and helical amylose and the branched amylopectin. Depending on the plant, starch generally contains 20 to 25% amylose and 75 to 80%
- 28. amylopectin by weight. Glycogen, the glucose store of animals, is a more highly branched version of amylopectin. In industry, starch is converted into sugars, for example by malting, and fermented to produce ethanol in the manufacture of beer, whisky and biofuel. It is processed to produce many of the sugars used in processed foods. Mixing most starches in warm water produces a paste, such as wheatpaste, which can be used as a thickening, stiffening or gluing agent. The biggest industrial non-food use of starch is as an adhesive in the papermaking process. Starch can be applied to parts of some garments before ironing, to stiffen them. Starch molecules arrange themselves in the plant in semi- crystalline granules. Each plant species has a unique starch granular size: rice starch is relatively small (about 2 μm) while potato starches have larger granules (up to 100 μm). Starch becomes soluble in water when heated. The granules swell and burst, the semi-crystalline structure is lost and the smaller amylose molecules start leaching out of the granule, forming a network that holds water and increasing the mixture's viscosity. This process is called starch gelatinization. During cooking, the starch becomes a paste and increases further in viscosity. During cooling or prolonged storage of the paste, the semi-crystalline structure partially recovers and the starch paste thickens, expelling water. This is mainly caused by retrogradation of the amylose. This process is responsible for the hardening of bread or staling, and for the water layer on top of a starch gel (syneresis).
- 29. Uses Corrugated board adhesives are the next largest application of non- food starches globally. Starch glues are mostly based on unmodified native starches, plus some additive such as borax and caustic soda. Papermaking is the largest non-food application for starches globally, consuming many millions of metric tons annually. In a typical sheet of copy paper for instance, the starch content may be as high as 8%. Both chemically modified and unmodified starches are used in papermaking Textile chemicals from starch: warp sizing agents are used to reduce breaking of yarns during weaving. Starch is mainly used to size cotton based yarns. Modified starch is also used as textile printing thickener. In oil exploration, starch is used to adjust the viscosity of drilling fluid, which is used to lubricate the drill head and suspend the grinding residue in petroleum extraction. Starch is also used to make some packing peanuts, and some drop ceiling tiles. In the printing industry, food grade starch is used in the manufacture of anti-set-off spray powder used to separate printed sheets of paper to avoid wet ink being set off. For body powder, powdered corn starch is used as a substitute for talcum powder, and similarly in other health and beauty products. Starch is used to produce various bioplastics, synthetic polymers that are biodegradable. An example is polylactic acid based on glucose from starch. Glucose from starch can be further fermented to biofuel corn ethanol using the so-called wet milling process. Today most bioethanol
- 30. production plants use the dry milling process to ferment corn or other feedstock directly to ethanol. Hydrogen production could use glucose from starch as the raw material, using enzyme Clothing or laundry starch is a liquid prepared by mixing a vegetable starch in water (earlier preparations also had to be boiled), and is used in the laundering of clothes.
- 31. 11.Protein Proteins are compounds composed of carbon, hydrogen, oxygen , and nitrogen , which are arranged as strands of amino acids . They play an essential role in the cellular maintenance, growth, and functioning of the human body. Serving as the basic structural molecule of all the tissues in the body, protein makes up nearly 17 percent of the total body weight. To understand protein's role and function in the human body, it is important to understand its basic structure and composition.
- 32. Amino Acids Amino acids are the fundamental building blocks of protein. Long chains of amino acids, called polypeptides, make up the multicomponent, large complexes of protein. The arrangement of amino acids along the chain determines the structure and chemical properties of the protein. Amino acids consist of the following elements: carbon, hydrogen, oxygen, nitrogen, and, sometimes, sulfur. The general structure of amino acids consists of a carbon center and its four substituents, which consists of an amino group (NH2), an organic acid (carboxyl) group (COOH), a hydrogen atom (H), and a fourth group, referred to as the R-group, that determines the structural identity and chemical properties of the amino acid. The first three groups are common to all amino acids. The basic amino acid structure is R- CH(NH2)-COOH. There are twenty different forms of amino acids that the human body utilizes. These forms are distinguished by the fourth variable substituent, the R-group, which can be a chain of different lengths or a carbon-ring structure. For example, if hydrogen represents the R-group, the amino acid is known as glycine, a polar but uncharged amino acid, while methyl (CH3) group is known as alanine, a nonpolar amino acid. Thus, the chemical components of the R-group essentially determine the identity, structure, and function of the amino acid. The structural and chemical relatedness of the R-groups allows classification of the twenty amino acids into chemical groups. Amino acids can be classified according to optical activity (the ability to polarize light), acidity and basicity, polarity and nonpolarity, or
- 33. hydrophilicity (water-loving) and hydrophobicity (water-fearing). These categories offer clues to the function and reactivity of the amino acids in proteins. The biochemical properties of amino acids determine the role and function of protein in the human body. Different types of Protein Name AbbreviationLinear structure formula (atom composition and bonding) Alanine ala CH3-CH(NH2)-COOH Arginine arg HN=C(NH2)-NH-(CH2)3-CH(NH2)- COOH Asparagine asn H2N-CO-CH2-CH(NH2)-COOH Aspartic acid asp HOOC-CH2-CH(NH2)-COOH Cysteine cys HS-CH2-CH(NH2)-COOH Glutamine gln H2N-CO-(CH2)2-CH(NH2)-COOH Glutamic acid glu HOOC-(CH2)2-CH(NH2)-COOH Glycine gly NH2-CH2-COOH Histidine his NH-CH=N-CH=C-CH2-CH(NH2)- COOH |____________| (nitrogen bonded to carbon) Isoleucine ile CH3-CH2-CH(CH3)-CH(NH2)-COOH
- 34. Name AbbreviationLinear structure formula (atom composition and bonding) Leucine leu (CH3)2-CH-CH2-CH(NH2)-COOH Lysine lys H2N-(CH2)4-CH(NH2)-COOH Methionine met CH3-S-(CH2)2-CH(NH2)-COOH Phenylalaninephe Ph-CH2-CH(NH2)-COOH Proline pro NH-(CH2)3-CH-COOH |__________| Serine ser HO-CH2-CH(NH2)-COOH Threonine thr CH3-CH(OH)-CH(NH2)-COOH Tryptophan trp Ph-NH-CH=C-CH2-CH(NH2)-COOH |_________| Tyrosine tyr HO-Ph-CH2-CH(NH2)-COOH Valine val (CH3)2-CH-CH(NH2)-COOH
- 35. 12.Wool Wool, animal fibre forming the protective covering, or fleece, of sheep or of other hairy mammals, such as goats and camels. Prehistoric man, clothing himself with sheepskins, eventually learned to make yarn and fabric from their fibre covering. Selective sheep breeding eliminated most of the long, coarse hairs forming a protective outer coat, leaving the insulating fleecy undercoat of soft, fine fibre. Wool is mainly obtained by shearing fleece from living animals, but pelts of slaughtered sheep are sometimes treated to loosen the fibre, yielding an inferior type called pulled wool. Cleaning the fleece removes ―wool grease,‖ the fatty substance purified to make lanolin (q.v.), a by-product employed in cosmetics and ointments. Wool fibre is chiefly composed of the animal protein keratin. Protein substances are more vulnerable to chemical damage and unfavourable environmental conditions than the cellulose material
- 36. forming the plant fibres. Coarser than such textile fibres as cotton, linen, silk, and rayon, wool has diameters ranging from about 16 to 40 microns (a micron is about 0.00004 inch). Length is greatest for the coarsest fibres. Fine wools are about 1.5 to 3 inches (4 to 7.5 centimetres) long; extremely coarse fibres may be as much as 14 inches in length. Wool is characterized by waviness with up to 30 waves per inch (12 per centimetre) in fine fibres and 5 per inch (2 per centimetre) or less in coarser fibres. Colour, usually whitish, may be brown or black, especially in coarse types, and coarse wools have higher lustre than fine types. Single wool fibres can resist breakage when subjected to weights of 0.5 to 1 ounce (15 to 30 grams) and when stretched as much as 25 to 30 percent of their length. Unlike vegetable fibres, wool has a lower breaking strength when wet. The resilient fibre can return to its original length after limited stretching or compression, thus imparting to fabrics and garments the ability to retain shape, drape well, and resist wrinkling. Because crimp encourages fibres to cling together, even loosely twisted yarns are strong, and both crimp and resilience allow manufacture of open-structured yarns and fabrics that trap and retain heat-insulating air. The low density of wool allows manufacture of lightweight fabrics. Wool fibre has good to excellent affinity for dyestuffs. Highly absorbent, retaining as much as 16 to 18 percent of its weight in moisture, wool becomes warmer to the wearer as it absorbs moisture from the air, thus adjusting its moisture content and, consequently, its weight, in response to atmospheric conditions. Because moisture absorption and release are gradual, wool is slow to feel damp and does not chill the wearer by too-rapid drying.
- 37. Wool that has been stretched during yarn or fabric manufacture may undergo relaxation shrinkage in washing, with fibres resuming their normal shape. Felting shrinkage occurs when wet fibres, subjected to mechanical action, become matted into packed masses. Wool has good resistance to dry-cleaning solvents, but strong alkalies and high temperatures are harmful. Washing requires the use of mild reagents at temperatures below 20° C (68° F), with minimum mechanical action. The performance of wool has been improved by development of finishes imparting insect and mildew resistance, shrinkage control, improved fire resistance, and water repellency. Woolen yarns, usually made from shorter fibres, are thick and full and are used for such full-bodied items as tweed fabrics and blankets. Worsteds, usually made from longer fibre, are fine, smooth, firm, and durable. They are used for fine dress fabrics and suitings. Wool that has had no previous use is described as new wool, or, in the United States, as virgin wool. The limited world supply results in the use of recovered wools. In the United States, wool recovered from fabric never used by the consumer is called reprocessed wool; wool recovered from material that has had use is called reused wool. Recovered wools, employed mainly in woolens and blends, are often of inferior quality because of damage suffered during the recovery process. Australia, Russia, New Zealand, and Kazakhstan lead in fine-wool production, and India leads in the production of the coarser wools known as carpet wools. Leading consumers include the United Kingdom, the United States, and Japan.
- 38. 13.SILK Silk, animal fibre produced by certain insects and arachnids as building material for cocoons and webs, some of which can be used to make fine fabrics. In commercial use, silk is almost entirely limited to filaments from the cocoons of domesticated silkworms (caterpillars of several moth species belonging to the genus Bombyx). See also sericulture. Origins In China The origin of silk production and weaving is ancient and clouded in legend. The industry undoubtedly began in China, where, according to native record, it existed from sometime before the middle of the 3rd millennium BCE. At that time it was discovered that the
- 39. roughly 1 km (1,000 yards) of thread that constitutes the cocoon of the silkworm could be reeled off, spun, and woven, and sericulture early became an important feature of the Chinese rural economy. A Chinese legend says that it was the wife of the mythological Yellow Emperor, Huangdi, who taught the Chinese people the art; throughout history the empress was ceremonially associated with sericulture. The weaving of damask probably existed in the Shang dynasty, and the tombs of the 4th– 3rd centuries BCE at Mashan near Jiangling (Hubei province), excavated in 1982, have provided outstanding examples of brocade, gauze, and embroidery with pictorial designs as well as the first complete garments. Eventually a strong demand for the local production of raw silk arose in the Mediterranean area. Justinian I, Byzantine emperor from 527 to 565, persuaded two Persian monks who had lived in China to return there and smuggle silkworms to Constantinople (now Istanbul) in the hollows of their bamboo canes (c. 550 CE). These few hardy silkworms were the beginning of all the varieties that stocked and supplied European sericulture until the 19th century.
- 40. Silk culture flourished in Europe for many centuries, especially in the Italian city-states and (from 1480) in France. In 1854, however, a devastating silkworm plague appeared. Louis Pasteur, who was asked to study the disease in 1865, discovered the cause and developed a means of control. The Italian industry recovered, but that of France never did. Meanwhile Japan was modernizing its methods of sericulture, and soon it was supplying a large portion of the world’s raw silk. During and after World War II the substitution of such man-made fibres as nylon in making hosiery and other garments greatly reduced the silk industry. Still, silk has remained an important luxury material and remains an important product of China, Japan, South Korea, and Thailand.
- 41. 14.Collagen Collagen is a structural protein that is the main support of skin, tendon, bone, cartilage and connective tissue. Collagen occurs naturally in the body and is a strong and fibrous substance. It is a major protein that forms the white fibres of connective tissue and makes up roughly 25 to 35 per cent of whole-body protein content for mammals. 29 types of collagen have been discovered, but the human body typically only produces five of these. Sometimes described as the building blocks of the body, collagen is an essential structural component of all connective tissue. The level of collagen in skin is worn away over time and natural ageing gradually wears away the collagen in skin. This causes the skin to crease and encourages the formation of lines and wrinkles as the skin loses elasticity.
- 43. Collagen and cosmetic treatments The loss of collagen can have an ageing effect on the appearance of the skin. A variety of collagen replacement therapies and treatments have been developed to replenish skin and connective tissues. Non surgical cosmetic treatments to combat the effects of ageing caused by collagen depreciation include dermal fillers. These can work as a collagen replacement therapy for the face by restoring the tone and elasticity of the skin. Line and wrinkle treatments can relax the muscles under the skin and smooth out lines caused by the inevitable loss of collagen over time.
- 44. Collagen dressings can help heal: chronic wounds that do not respond to other treatment wounds that expel bodily fluids such as urine or sweat granulating wounds, on which different tissue grows necrotic or rotting wounds partial and full-thickness wounds second-degree burns sites of skin donation and skin grafts
- 45. 15.Nucleic acids Nucleic acids are a family of macromolecules that includes deoxyribonucleic acid (DNA ) and multiple forms of ribonucleic acid (RNA ). DNA, in humans and most organisms, is the genetic material and represents a collection of instructions (genes) for making the organism. This collection of instructions is called the genome of the organism. The primary classes of RNA molecules either provide information that is used to convert the genetic information in DNA into functional proteins, or are important players in the translational process , in which the actual process of protein synthesis (on ribosomes ) occurs.
- 46. Types Of Nucleic Acids: Composition And Structure All nucleic acids are linear, nonbranching polymers of nucleotides, and are therefore polynucleotides. DNA is double-stranded in virtually all organisms. (It is single-stranded in some viruses.) DNA occurs in many, but not all, small organisms as double-stranded and circular (without any ends). Higher organisms (eukaryotes) have approximately ten million base pairs or more, with the genetic material parceled out into multiple genetic pieces called chromosomes. For example, humans have twenty-three pairs of chromosomes in the nucleus of each somatic cell . Within the nucleus, the DNA molecules are found in "looped arrangements" that mimic the circular DNA observed in many prokaryotes. All RNA molecules are single-stranded molecules. RNA molecules are synthesized from DNA templates in a process known as transcription ; these molecules have a number of vital roles within cells. It is convenient to divide RNA molecules into the three functional classes, all of which function in the cytoplasm. All nucleic acids are polynucleotides, with each nucleotide being made up of a base, a sugar unit, and a phosphate. The composition of DNA differs from that of RNA in two major ways (see Figure). Whereas DNA contains the bases guanine (G), cytosine (C), adenine (A), and thymine (T), RNA contains G, C, and A, but it contains uracil (U) in place of thymine. Both DNA and RNA contain a five- membered cyclic sugar (a pentose). RNA contains a ribose sugar. The sugar in DNA, however, is 2′-deoxyribose.
- 47. In DNA, each base is linked by a β -glycosidic bond to the C1′ position of the 2′-deoxyribose, and each phosphate is linked to either the C3′ or C5′ position. The linkages are essentially the same in RNA. DNA is a right-handed, double-stranded helix, in which the bases essentially occupy the interior of the helix, whereas the phosphodiester backbone (sugar-phosphate backbone) more or less comprises the exterior. The bases on the individual strands form intermolecular hydrogen bonds with each other (the complementary Watson–Crick base pairs). An adenine base on one strand interacts specifically with a thymine base on the other, forming two hydrogen bonds and an A–T base pair; while a G–C base pair contains three hydrogen bonds. These interactions possess a specificity that is pivotal to both DNA replication and transcription .As stated previously, DNA is the genetic material in humans and in virtually all organisms, including viruses—with the exception of a few viruses that possess RNA as the genetic material. In complex multicellular organisms (such as humans), DNA carries within itself the instructions for the synthesis and assembly of virtually all the components of the cell and (therefore) for the structure and function of tissues and organs. Within the approximately 3.2 × 109 base pairs (3.2 Gbps) in human DNA, the Human Genome Project has determined that there are a minimum of about 25,000 individual segments that correspond to individual genes. The genes collectively make up only about 2 to 3 percent of the total DNA, but encode the detailed genetic instructions for the synthesis of proteins. Proteins are the "workhorses" of the cell, and in one way or another are responsible for the functions that permit a cell to communicate with other cells and that define the character of the individual cell. A kidney cell is very
- 48. different from a heart or eye cell. Although every cell contains the same DNA, different subsets of the 25,000 genes are expressed in the different organs or tissues. The expressed genes determine the type of cell that is produced and a cell's ultimate function in a multicellular organism. Interestingly, there is only approximately a 0.1 percent difference in DNA among humans. The nucleotide sequences of DNA differs between organisms and is a fundamental difference between individuals and between species. For example, our closest (species) relative, the chimpanzee, has DNA that is 98.5 percent identical to that of humans.