Answer: <h3>Carbohydrate</h3>
<h4>Introduction:</h4>
<p>Carbohydrates are one of the main types of nutrients. They are the most important source of energy for your body. Your digestive system changes carbohydrates into glucose (blood sugar). Your body uses this sugar for energy for your cells, tissues, and organs. It stores any extra sugar in your liver and muscles for when it is needed.</p>
<p>Carbohydrates are called simple or complex, depending on their chemical structure. Simple carbohydrates include sugars found naturally in foods such as fruits, vegetables, milk, and milk products. They also include sugars added during food processing and refining. Complex carbohydrates include whole grain bread and cereals, starchy vegetables and legumes. Many of the complex carbohydrates are good sources of fiber.</p>
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<p><img src="https://encrypted-tbn3.gstatic.com/images?q=tbn:ANd9GcS3BZ9PjHgfNfAZYXvOFyGfO8SlAg1oFQph5H2CNuwkdPPtQmix" alt="Image result for carbohydrates" /></p>
<h4>Definition:</h4>
<p>Carbohydrate is defined as &ldquo;aldehyde or ketone derivatives of higher polyhydric alcohols, or compounds which produce them on hydrolysis.&rdquo;</p>
<h4>Functions:</h4>
<ol>
<li><strong>Provide instant energy to the body</strong><em>:</em>This appears to be the primary function of carbohydrates in the body.</li>
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<p>Carbohydrates which we consume as food in the form of starch (ex: potato, bread), sucrose (ex: sugar, fruits)etc. get digested in the body to release glucose.This glucose after being absorbed into blood reaches all the body tissues and cell.</p>
<p>There it gets metabolized to release energy in the form of ATP in the presence of oxygen inside the mitochondria. Thus,energy is produced in the body due to a breakdown of carbohydrates and it is the prime function of carbohydrates.</p>
<ol start="2">
<li><strong>Reserve food for the body emergency</strong>: The excess glucose<u></u> in the body is converted to glycogen in the liver and stored there for future needs like in starvation. Some of the glycogen is also reserved in muscles. In times of starvation, this glycogen converts back to provide energy.</li>
<li><strong>Carbohydrates for other biomolecules</strong>: Carbohydrates in excess are converted into other bio-molecules of physiological importance like fats, by fatty acid synthesis reaction in the cell for storage in the body and use in times of starvation.</li>
<li><em><strong><u>Detoxification of the body by metabolism</u></strong></em>: Many drugs, toxic wastes in the body are metabolized for easy excretion in the body.</li>
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<p>Some of these are water insoluble and hence they are difficult to be expelled in urine. The body converts them into glucuronosyl conjugates using the glucuronosyl moiety derived from carbohydrates.</p>
<p>A carbohydrate moiety like glucose combines with a uronic acid to form glucuronate. These conjugates of insoluble substances with glucuronosyls are more water-soluble and easily excreted from the body. Thus, detoxification of physiological importance is carried out to some extent with carbohydrate derivatives.</p>
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<li><strong>As reaction intermediates or accessories</strong>: Carbohydrates participate as reaction intermediates in some vital reactions.</li>
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<p>This function of carbohydrates is seen extensively in various cellular reaction. For example, Vitamin B2 i.e Riboflavin has ribose sugar (4 carbon) a type of carbohydrate in its chemical structure and involved in vital reactions at a cellular level. As such carbohydrates are constituents of many hormones, vitamins, enzymes etc.</p>
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<li><strong>Constitutegenetic material</strong>: Carbohydrates form a part of genetic material like DNA and RNA in the form of deoxyribose and ribose sugars. This as carbohydrates from heptose sugars which are used to form ribose sugars (pseudo-heptose pathway)</li>
<li>They are constituents of all the cellular organelles like a cell membrane, mitochondria, nucleus, endoplasmic reticulum etc. in one or other way to give structural integrity.They help make up the body mass by being included in all the parts of the cell and tissues. For example, in cell membranes, there are two constituents i.e. glycolipid layer and glycoprotein layer. Here the term &ldquo;glycol&rdquo; is a carbohydrate&hellip;&hellip;</li>
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<p>8.They form components of bio-molecules which have a key role in blood clotting, immunity,fertilization. Thus, they take part in many physiological reactions.</p>
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<li><strong>Transport of oxygen</strong>: Glucose is taken by red blood cells. These are the types of blood cells which lack mitochondria and other cell organelles required for production energy. In such case, the ATP is produced by non-oxidative pathway (lactose pathway). This energy thus produced is necessary for hemoglobin to bind to oxygen molecules and aid in the transfer of oxygen from lungs to the different tissues.</li>
<li><strong>Aid in gut motility</strong>: Carbohydrates form a fibrous material. When carbohydrates are digested, this material absorbs water in the guts, swells and increases the load. This load is useful to increase intestinal motility and expulsion of waste (feces). Thus, carbohydrates help clear gut and prevent constipation.</li>
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<h4>Classifications of carbohydrates:</h4>
<p>Carbohydrates are classified into three groups<br /><br /><strong>1. Monosaccharides or Monosachoroses</strong></p>
<p>From Greek,<em>mono</em>=one;<em>sakchron</em>=sugar.</p>
<p>Monosaccharides are often called simple sugars, these are a compound which possesses a free aldehyde or ketone group. They are the simplest sugars and cannot be hydrolyzed. The general formula is C<em>_n</em>(H<em>₂</em>O)<em>_n</em>or C<em>_n</em>H<em>_2n</em>O<em>_n</em>. The monosaccharides are subdivided into trioses, tetrose, pentoses, hexoses, heptoses etc., and also as aldoses or ketoses depending upon whether they contain aldehyde or ketone group.<br /><br />Examples of monosaccharides are Fructose, Erythrulose, Ribulose.<br /><br /><strong>2. Oligosaccharides or Oligosaccharides</strong></p>
<p>In Greek,Oligo means few.</p>
<p>Oligosaccharides are compound sugars that yield 2 to 10 molecules of the same or different monosaccharides on hydrolysis.</p>
<p>Oligosaccharides yielding 2 molecules of monosaccharides on hydrolysis is known as a disaccharide, and the ones yielding 3 or 4 monosaccharides are known as trisaccharides and tetrasaccharides respectively and so on. The general formula of disaccharides is C<em>_n</em>(H<em>₂</em>O)<em>_n-1</em>and that of trisaccharides is C<em>_n</em>(H<em>₂</em>O)<em>_n-2</em>and so on.<br /><br />An example of disaccharides is sucrose, lactose, maltose etc.<br />Trisaccharides are Raffinose,</p>
<p><strong>3. Polysaccharides or Polysaccharoses</strong></p>
<p>In Greek,poly means many.</p>
<p>Polysaccharides are compound sugars and yield more than 10 molecules of monosaccharides on hydrolysis. They are further classified depending on they type of molecules produced as a result of hydrolysis. They may be homopolysaccharides i.e, monosaccharides of the same type or heteropolysaccharides i.e., monosaccharides of different types. The general formula is(C₆H₁₀O₅)<em>_x</em>_{.<br />}<br />An example of homopolysaccharides is starch, glycogen, cellulose, pectin.<br />Heteropolysaccharides areHyaluronic acid, Chondroitin.</p>
<h4>Composition of carbohydrate:</h4>
<p>There are three types of structural representations of carbohydrates:</p>
<ul>
<li>Open chain structure.</li>
<li>Hemi-acetal structure.</li>
<li>Haworth structure.</li>
</ul>
<p><strong>Open chain structure</strong>- It is the long straight chain form of carbohydrates.<br />Example:<br /><em>Hemi-acetal structure</em>- Here the 1st carbon of the glucose condenses with the -OH group of the 5th carbon to form a ring structure.<br /><em>Haworth structure</em>- It is the presence of pyranose ring structure.</p>
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