The Cell living organisms.

The cell is the structural and functional unit of all known living organisms. It is the smallest unit of an organism that is classified as living, and is often called the building block of life. Some organisms, such as most bacteria, are unicellular (consist of a single cell). Other organisms, such as humans, are multicellular. (Humans have an estimated 100 trillion or 1014 cells; a typical cell size is 10 µm; a typical cell mass is 1 nanogram.) The largest known cell is an unfertilized ostrich egg cell.

General principles

Each cell is at least somewhat self-contained and self-maintaining: it can take in nutrients, convert these nutrients into energy, carry out specialized functions, and reproduce as necessary. Each cell stores its own set of instructions for carrying out each of these activities.

All cells have several different abilities:

Reproduction by cell division: (binary fission/mitosis or meiosis).

• Use of enzymes and other proteins coded for by DNA genes and made via messenger RNA intermediates and ribosomes.

• Metabolism, including taking in raw materials, building cell components, converting energy, molecules and releasing by-products. The functioning of a cell depends upon its ability to extract and use chemical energy stored in organic molecules. This energy is released and then used in metabolic pathways.

• Response to external and internal stimuli such as changes in temperature, pH or levels of nutrients.

• Cell contents are contained within a cell surface membrane that is made from a lipid bilayer with proteins embedded in it.

Some prokaryotic cells contain important internal membrane-bound compartments, but eukaryotic cells have a specialized set of internal membrane compartments.

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DNA replication

DNA replication, the basis for biological inheritance, is a fundamental process occurring in all living organisms to copy their DNA. This process is "semiconservative" in that each strand of the original double-stranded DNA molecule serves as template for the reproduction of the complementary strand. Hence, following DNA replication, two identical DNA molecules have been produced from a single double-stranded DNA molecule. Cellular proofreading and error-checking mechanisms ensure near perfect fidelity for DNA replication. In a cell, DNA replication begins at specific locations in the genome, called "origins". Unwinding of DNA at the origin, and synthesis of new strands, forms a replication fork. In addition to DNA polymerase, the enzyme that synthesizes the new DNA by adding nucleotides matched to the template strand, a number of other proteins are associated with the fork and assist in the initiation and continuation of DNA synthesis

DNA replication can also be performed in vitro (outside a cell). DNA polymerases, isolated from cells, and artificial DNA primers are used to initiate DNA synthesis at known sequences in a template molecule. The polymerase chain reaction (PCR), a common laboratory technique, employs such artificial synthesis in a cyclic manner to amplify a specific target DNA fragment from a pool of DNA.

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Steps of DNA Replication

1)The first major step for the DNA Replication to take place is the breaking of hydrogen bonds between bases of the two antiparallel strands. The unwounding of the two strands is the starting point. The splitting happens in places of the chains which are rich in A-T. That is because there are only two bonds between Adenine and Thymine (there are three hydrogen bonds between Cytosine and Guanine). Helicase is the enzyme that splits the two strands. The initiation point where the splitting starts is called "origin of replication".The structure that is created is known as "Replication Fork".

2) One of the most important steps of DNA Replication is the binding of RNA Primase in the the initiation point of the 3'-5' parent chain. RNA Primase can attract RNA nucleotides which bind to the DNA nucleotides of the 3'-5' strand due to the hydrogen bonds between the bases. RNA nucleotides are the primers (starters) for the binding of DNA nucleotides. because 3) The elongation process is different for the 5'-3' and 3'-5' template. a)5'-3' Template: The 3'-5' proceeding daughter strand -that uses a 5'-3' template- is called leading strandDNA Polymerase ä can "read" the template and continuously adds nucleotides (complementary to the nucleotides of the template, for example Adenine opposite to Thymine etc). b)3'-5'Template: The 3'-5' template cannot be "read" by DNA Polymerase ä. The replication of this template is complicated and the new strand is called lagging strand. In the lagging strand the RNA Primase adds more RNA Primers. DNA polymerase å reads the template and lengthens the bursts. The gap between two RNA primers is called "Okazaki Fragments". The RNA Primers are necessary for DNA Polymerase å to bind Nucleotides to the 3' end of them. The daughter strand is elongated with the binding of more DNA nucleotides. 4) In the lagging strand the DNA Pol I -exonuclease- reads the fragments and removes the RNA Primers. The gaps are closed with the action of DNA Polymerase (adds complementary nucleotides to the gaps) and DNA Ligase (adds phosphate in the remaining gaps of the phosphate - sugar backbone). Each new double helix is consisted of one old and one new chain. This is what we call semiconservative replication. 5) The last step of DNA Replication is the Termination. This process happens when the DNA Polymerase reaches to an end of the strands. We can easily understand that in the last section of the lagging strand, when the RNA primer is removed, it is not possible for the DNA Polymerase to seal the gap (because there is no primer). So, the end of the parental strand where the last primer binds isn't replicated. These ends of linear (chromosomal) DNA consists of noncoding DNA that contains repeat sequences and are called telomeres. As a result, a part of the telomere is removed in every cycle of DNA Replication. 6) The DNA Replication is not completed before a mechanism of repair fixes possible errors caused during the replication. Enzymes like nucleases remove the wrong nucleotides and the DNA Polymerase fills the gaps. Similar processes also happen during the steps of DNA Replication of prokaryotes though there are some differences

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Nucleic Acids - DNA - RNA

DNA is composed of four types of molecules known as nucleic acids or nucleotides. The four nucleotides are: adenine (A), guanine (G), cytosine (C), and thymine (T). These molecules are further classified into two families. Adenine (A) and guanine (G) are known as purine and cytosine (C) and thymine (T) are known as pyrimidine. During DNA synthesis, nucleotides are converted into nucleic acids to so that they can be linked to form strands of DNA. The assembled strand of DNA takes on the structure of a double helix.

The two strands of DNA are held together by hydrogen bonds between adjacent complementary nucleotides.

The chemical structures of the four nucleotides are planar due to the delocalized electrons in the five- and six-membered rings, each having a thickness of 3.4 angstroms. When the nucleotides form the double helix structure, A-T and G-C are joined together by a hydrogen bond to form a base pair. The base pairs are then joined together by sugar bonds to form the helix. X-ray data shows that there are 10 base pairs per turn of the helix.

The helical model of DNA also explains the theory of genetic replication. James Watson once described it as the "pretty molecule" because the method of replication is so self evident in this structure. During replication, the hydrogen bonds between nucleotides break and allow each single strand of DNA to serve as a template for replication of the other half. The two identical copies of newly synthesized of DNA are then distributed to two new daughter cells. Because during each cycle of replication half of the old DNA is preserved, DNA replication is said to be semi-conservative.

Although DNA contains the genetic blueprint of life, it requires the assistance of ribonucleic acid (RNA) to be functional. RNA also consists of strands of nucleic acids joined together by sugar-phosphate bonds. Unlike DNA, RNA substitutes the nucleotide thymine (T) with uracil (U) and exists as single strands. After DNA is converted into strands of RNA, the messenger RNA (mRNA) is sent to the ribosome to direct the synthesis of proteins.

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Polysaccharides - Introduction

Polysaccharides: They consist of repeat units of monosaccharides or their derivatives. These units are held by glycosidic bonds. These carbohydrates liberate large number of monosaccharide molecules on hydrolysis. They are colorless and tasteless. So, they are called non-sugars. They are concerned with two important functions - structural and storage of energy. Some examples of polysaccharides are starch, cellulose, glycogen and dextrins. However starch and cellulose are the most important of these. Polysaccharides are linear as well as branched polymers. The general formula is (C6H10O5)n, where 'n' stands for a very large number. The occurrence of branches in polysaccharides is due to the glycosidic linkages formed at any one of the hydroxyl groups of a monosaccharide.

POLYSACCHARIDES are condensation polymers of simpler units called MONOSACCHARIDES, which belong to a very large group of organic molecules called CARBOHYDRATES, that is, molecules that contain only carbon, hydrogen and oxygen . A simple monosaccharide, glucose, has the structure shown here on the left. Amylose is a glucose polymer with a(1®4) glycosidic linkages, as represented above (see also diagram p. 366). The end of the polysaccharide with an anomeric carbon (C1) that is not involved in a glycosidic bond is called the reducing end.

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Maltose (C12H22O11)

Maltose (C₁₂H₂₂O₁₁) Maltose is made up of two a-D-glucose (in pyranose form) units held together by a(14) glycosidic bond. As there is a free aldehyde group at C-1 position of the second glucose molecule, maltose is known as reducing sugar. Maltose forms osazones. The enzyme that hydrolyses maltose is maltase.

or

The structure of cellobiose, a disaccharide is similar to maltose. They differ in the glycosidic linkage. The linkage of cellobiose is b(14). Maltose is obtained by partial hydrolysis of starch by diastase an enzyme present in malt (sprouted barley seeds).

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Carbohydrates - Introduction

Introduction:

General names for carbohydrates include sugars, starches, saccharides, and polysaccharides. The term saccharide is derived from the Latin word " sacchararum" from the sweet taste of sugars.

The name "carbohydrate" means a "hydrate of carbon." The name derives from the general formula of carbohydrate is C_x(H₂O)_y - x and y may or may not be equal and range in value from 3 to 12 or more. For example glucose is: C₆(H₂O)₆ or is more commonly written, C₆H₁₂O₆.

The chemistry of carbohydrates most closely resembles that of alcohol, aldehyde, and ketone functional groups. As a result, the modern definition of a CARBOHYDRATE is that the compounds are polyhydroxy aldehydes or ketones. The chemistry of carbohydrates is complicated by the fact that there is a functional group (alcohol) on almost every carbon. In addition, the carbohydrate may exist in either a straight chain or a ring structure. Ring structures incorporate two additional functional groups: the hemiacetal and acetal.

A major part of the carbon cycle occurs as carbon dioxide is converted to carbohydrates through photosynthesis. Carbohydrates are utilized by animals and humans in metabolism to produce energy and other compounds.

Carbohydrate Functions:

Carbohydrates are initially synthesized in plants from a complex series of reactions involving photosynthesis.

-Store energy in the form of starch (photosynthesis in plants) or glycogen (in animals and humans).

-Supply carbon for synthesis of other compounds.

-Form structural components in cells and tissues.

Photosynthesis is a complex series of reactions carried out by algae, phytoplankton, and the leaves in plants, which utilize the energy from the sun. The simplified version of this chemical reaction is to utilize carbon dioxide molecules from the air and water molecules and the energy from the sun to produce a simple sugar such as glucose and oxygen molecules as a by product. The simple sugars are then converted into other molecules such as starch, fats, proteins, enzymes, and DNA/RNA i.e. all of the other molecules in living plants. All of the "matter/stuff" of a plant ultimately is produced as a result of this photosynthesis reaction.

Metabolism: Metabolism occurs in animals and humans after the ingestion of organic plant or animal foods. In the cells a series of complex reactions occurs with oxygen to convert for example glucose sugar into the products of carbon dioxide and water and ENERGY. This reaction is also carried out by bacteria in the decomposition/decay of waste materials on land and in the water.

Combustion occurs when any organic material is reacted (burned) in the presence of oxygen to give off the products of carbon dioxide and water and ENERGY. The organic material can be any fossil fuel such as natural gas (methane), oil, or coal. Other organic materials that combust are wood, paper, plastics, and cloth.

The whole purpose of both processes is to convert chemical energy into other forms of energy such as heat.

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Proteins

Proteins consist of strands of amino acids folded into a specific shape. The different protein structures can be classified by four levels of folding, each successive one being constructed from the preceding one.

Primary Structure - The very basic strand of amino acids is the called the primary structure.
Secondary Structure - The hydrogen-bond interaction among strands of amino acids gives rise to the first level of folding, alpha-helices and beta-sheets.
Tertiary - Interaction between alpha-helices and beta-sheets comprise the second level of folding, protein domains. These protein domains are then strung together through third level folding to form small globular proteins. The combination of second and third level folding yields tertiary structure.
Quaternary Structure - In order to achieve enhanced function, small globular proteins often come together to form protein aggregates. This fourth level of protein structure is called the quaternary structure. A famous example of quaternary structure is hemoglobin.

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Monosaccharide

Monosaccharides are the most basic unit of carbohydrates. They consist of one sugar and are usually colorless, water-soluble, crystalline solids. Some monosaccharides have a sweet taste. Examples of monosaccharides include glucose (dextrose), fructose (levulose), galactose, xylose and ribose. Monosaccharides are the building blocks of disaccharides such as sucrose and polysaccharides (such as cellulose and starch). Further, each carbon atom that supports a hydroxyl group (except for the first and last) is chiral, giving rise to a number of isomeric forms all with the same chemical formula. For instance, galactose and glucose are both aldohexoses, but have different chemical and physical properties.

Cyclic structure

Most monosaccharides will cyclize in aqueous solution, forming hemiacetals or hemiketals (depending on whether they are aldoses or ketoses) between an alcohol and the carbonyl group of the same sugar. Glucose, for example, readily forms a hemiacetal linkage between its carbon1 and oxygen5 to form a 6-membered ring called a pyranoside. The same reaction can take place between carbon1 and oxygen4 to form a 5-membered furanoside. In general, pyranosides are more stable and are the major form of the monosaccharide observed in solution. Since cyclization forms a new stereogenic center at carbon1, two anomers can be formed (α-isomer and β-isomer) from each distinct straight-chain monosaccharide. The interconversion between these two forms is called mutarotation.

α-D-Glucopyranose

β-D-Glucopyranose.

A common way of representing the structure of monosaccharides is the Haworth projection. In a Haworth projection, the α-isomer has the OH- of the anomeric carbon below the plane of the carbon atoms, and the β-isomer, has the OH- of the anomeric carbon above the plane. Monosaccharides typically adopt a chair conformation, similar to cyclohexane. In this conformation the α-isomer has the OH- of the anomeric carbon in an axial position, whereas the β-isomer has the OH- of the anomeric carbon in equatorial position.

Isomerism

The total number of possible stereoisomers of one compound (n) is dependent on the number of stereogenic centers (c) in the molecule. The upper limit for the number of possible stereoisomers is n = 2c. The only carbohydrate without an isomer is dihydroxyacetone or DHA.

Monosaccharides are classified according to their molecular configuration at the chiral carbon furthest removed from the aldehyde or ketone group. The chirality at this carbon is compared to the chirality of carbon 2 on glyceraldehyde. If it is equivalent to D-glyceraldehyde's C2, the sugar is D; if it is equivalent to L-glyceraldehyde's C2, the sugar is L. Due to the chirality of the sugar molecules, an aqueous solution of a D or L saccharides will rotate light. D-glyceraldehyde causes polarized light to rotate clockwise (dextrorotary); L-glyceraldehyde causes polarized light to rotate counterclockwise (levorotary). Unlike glyceraldehyde, D/L designation on more complex sugars is not associated with their direction of light rotation. Since more complex sugars contain multiple chiral carbons, the direction of light rotation cannot be predicted by the chirality of the carbon that defines D/L nomenclature.

• D, configuration as in D-glyceraldehyde

• L, configuration as in L-glyceraldehyde

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Biomolecules-IV

Synthesis of proteins - Transcription and Translation Transcription This is a process in which RNA is synthesized from DNA. Among the two strands of DNA one strand serves as template and is called as coding strand where as the other strand is called as non-coding strand as it does not participate in transcription. Transcription involves three different stages. Genetic Code Genetic code is the dictionary of nucleotide bases, which determines the sequence of amino acids in proteins. The genetic code (or) codons have triplet base sequences in m RNA, which act as code words for amino acids. The DNA sequence that code for a specific protein(or) polypeptide is called a gene. There are 4 different bases in m RNA - A, G, C and U. They produce 64 different triplets (43). Out of 64 codons 61 codons code for 20 amino acids. The 3 codons UAA, UAG and UGA do not code for amino acids and they are called non-sense codons. The codons AUG and GUG are called initiating codons. Mutation Mutation is defined as a chemical change in the DNA structure of a gene. A difference of a single base in the DNA molecule or a single error in the reading of the code can cause a change in the amino acid sequence which leads to mutation. Lipids Lipids are organic substances present in all living organisms. They include fats, oils, waxes and other related compounds. They are insoluble in water and hydrophobic, and soluble in organic solvents. They are related to fatty acids and are not polymers. They are esters of long chain fatty acids and alcohols. Hormones Hormones are the chemical messengers of the body. They are defined as organic substances secreted into blood stream to control the metabolic and biological activities. These hormones are involved in transmission of information from one tissue to another and from cell to cell. These substances are produced in small amounts by various endocrine (ductless) glands in the body. They are delivered directly to the blood in minute quantities and are carried by the blood to various target organs where these exert physiological effect and control metabolic activities. Thus frequently their site of action is away from their origin. Hormonesare required in trace amounts and are highly specific in their functions. The deficiency of any hormones leads to a particular disease, which can be cured by administration of that hormone. Introduction Vitamins are the organic compounds required for the normal maintenance and health of an organism in minute quantities and their absence cause specific deficiency diseases. These are required in diet in order to perform specific biological functions. There are about 15 vitamins essential for humans. Plants can synthesize cell vitamins whereas only a few are synthesized in animals and hence need to be supplied in the foods. Classification of Vitamins Fat soluble vitamins These vitamins are soluble in fats, oils and in fat solvents like alcohol, etc. There are four fat soluble vitamins. They are: Vitamin A, Vitamin D, Vitamin E and Vitamin K. Some Important Vitamins Vitamin A This is a fat soluble vitamin which is present mostly in animals. Its provitamins carotenes are found in plants. Vitamin A is necessary for vision and proper growth. It is necessary for maintenance of proper immune system to fight various infections. Cholesterol synthesis requires vitamin A. The carotenoids act as antioxidants and reduce risk of cancers. Functions of Vitamins in Biosystems Vitamins are the important food factors required in diet. Different vitamins are involved in different biochemical functions. They are required in very low concentration, the daily requirement of any vitamin for any individual is extremely smell. The daily dose of any vitamin is not a fixed quantity but varies according to size, age and rate of metabolism of the individual. Youngsters need higher quantity of vitamins then elders and their requirement increases when a person performs exercise. Growing children and pregnant mothers need more quantity of vitamins in their diet.

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Biomolecules-III

Structures of Amino Acids Amino acids are the building blocks of proteins. There are 300 amino acids that occur in nature. Among these only 20 are known as standard amino acids that commonly occur in proteins. Amino acids contain two functional groups. They are - amino and carboxyl groups. The amino group (-NH2) is basic and the carboxyl group (-COOH) is acidic in nature. Nomenclature of Amino Acids All amino acids have trivial names. IUPAC names which even if not cumbersome are not used. For e.g., H2N CH2COOH is better known as glycine rather then a-amino acetic acid or 2-amino ethanoic acid. Classification of Amino Acids Base on Polarity Amino acids are classified into different ways based on polarity, structure, nutritional requirement, metabolic fate, etc. Generally used classification is based on polarity. Classification of Amino Acids Based on Nutrition The amino acids that are to be supplied through diet are called as essential amino acids. They cannot be produced by the body. The essential amino acids are arginine, valine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine and tryptophan. Physical Properties of a-Amino Acids Amino acids are colourless, crystalline solids. They are water-soluble high melting solids and behave like salts. The a-carbon atom has 'R' which is a side chain. This side chain is different for different amino acids. The carboxyl and amino groups interact resulting in the transfer of proton from carboxyl group to amino group. Thus the amino acid exists in ionised form known as zwitter ion. This explains the physical properties of these a-amino acids. Iso-electric Point It is defined as the point at which a molecule exists as zwitter ion with no net charge. Thus, at this point the molecule is electrically neutral. The molecules have minimum solubility, maximum precipitability and least buffer capacity. The acidic amino acids and basic amino acids strongly influence the iso-electric point (PI). The PI value of protein is determined by the nature of ionizable groups of amino acids. By taking average Pka values of ionisable groups PI value can be calculated. Chemical properties of a-amino acids When two amino acids combine with each other, the amino group of one amino acid combines with carboxyl group of other amino acid. This leads to peptide bond formation. The combination of the amino group of one molecule with the carboxyl group of the other results in the elimination of a water molecule and forms a -CO-NH-bond. Poly Peptides Peptides containing more than 10 amino acids are called poly peptides. Poly peptides are formed by the linear sequence of amino acids. Some proteins are composed of two or more poly peptide chains. Relatively shorter peptides are known as oligopeptides whereas longer polymers are called polypeptides. Polypeptides containing more than 100 amino acids having molecular mass higher then 10,000 are generally called as proteins. However the distinctive between a polypeptide and a protein is not sharp.

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Biomolecules -II

Maltose Maltose is made up of two a-D-glucose (in pyranose form) units held together by a(14) glycosidic bond. As there is a free aldehyde group at C-1 position of the second glucose molecule, maltose is known as reducing sugar. Maltose forms osazones. The enzyme that hydrolyses maltose is maltase. Lactose Lactose is made up of b-D-galactose and b-D-glucose held together by b(14) glycosidic bond. As the aldehyde group at C-1 position of glucose is free, lactose is known as reducing sugar. Lactose forms osazones. Polysaccharides - Introduction They consist of repeat units of monosaccharides or their derivatives. These units are held by glycosidic bonds. These carbohydrates liberate large number of monosaccharide molecules on hydrolysis. They are colorless and tasteless. So, they are called non-sugars. They are concerned with two important functions - structural and storage of energy. Some examples of polysaccharides are starch, cellulose, glycogen and dextrins. However starch and cellulose are the most important of these. Classification Mucopolysaccharides are the heteroglycans made of repeating units of sugar derivatives like amino sugars and uronic acids. These are known as glycosamino glycans (GAG). Important mucopolysaccharides are hyaluronic acid, chondroitin sulphate and heparin. Structures of Starch and Cellulose Starch occurs in all plants, particularly in their seeds. The main sources are wheat, maize, rice, potatoes, barley and sorghum. Functions of Carbohydrates Carbohydrates participate in a wide range of functions: * Carbohydrates are most abundant dietary source of energy for all organisms. * They supply energy and serve as storage form of energy. * Carbohydrates such as glucose, fructose, starch, glycogen, etc. provide energy for functioning of living organisms. Proteins - Introduction Proteins are the high molecular mass complex biopolymers of amino acids and organic compounds that are most important to life. They are essential for growth and maintenance of life. They are high molecular weight, nitrogen rich substances that are present all living cells of animals and plants. They occur in every part of the cell. They are composed of 20 amino acids, which are repeatedly found in the structure of proteins. These amino acids are liberated when proteins are hydrolyzed. Proteins are the polymers of -amino acids.

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Biomolecules-I

Introduction Biomolecules are complex organic molecules. These molecules form the basic structural constituent of a living cell. The organic compounds such as amino acids, nucleotides and monosaccharides serve as building blocks of complex biomolecules. The important biomolecules are proteins, carbohydrates and fats, enzymes, vitamins, hormones and nucleic acids. Some of the biomolecules are polymers. For e.g., starch, proteins, nucleic acids are condensation polymers of simple sugars, amino acids and nucleotides respectively. The Cell The cell is the fundamental structural and functional unit of living organisms. Cells need energy for active transport, to move molecules between the environment and the cells across cells or within cells. Cells obtain energy by oxidation of molecules like glucose. This oxidation takes place in a complex and controlled way by means of enzymes which are biocatalysts. Photosynthesis and Energy Energy for life processes basically comes from the sun. During photosynthesis, green plants absorb energy from the sun to make glucose and oxygen from carbon dioxide and water. Carbohydrates - Introduction Carbohydrates are the organic molecules that are composed of elements carbon, hydrogen and oxygen. These carbohydrates are referred to as saccharides. Carbohydrates are defined as polyhydroxy-aldehydes or polyhydroxy ketones or compounds, which produce them on hydrolysis. They supply energy and serve as structural constituents. Classification Carbohydrates are classified into three groups based on the number of sugar units and upon their behaviour towards hydrolysis. They are * Monosaccharides * Oligosaccharides and * Polysaccharides. Monosaccharides These are the simple carbohydrates that cannot be hydrolysed to simpler compounds. They are sweet to taste, crystalline and soluble in water. They are commonly known as sugars. They are further classified based on the functional group and number of carbon atoms. They are aldoses and ketoses. Monosaccharide - Glucose Glucose occurs in nature in free as well as combined form. It is present in sweet fruits and honey. Ripe grapes contain ~ 20% of glucose. Anomeric Carbon A pair of stereoisomers that differ in configurations around C-1 are called anomers and the C-1 carbon is called anomeric carbon. The a and b - cyclic forms of D-glucose are known as anomers. In this case, a-anomers of glucose contains the -OH group towards right at C-1 position and b-anomer of glucose contains the -OH group towards left at C-1 position. So, D-glucose exists in two stereo isomeric forms with different specific rotations and melting points. Sucrose Sucrose is made up of a-D-Glucose and b-D-fructose held together by a glycosidic bond, between C1 of a-glucose and C2 of b-fructose. The reducing groups of glucose and fructose are involved in glycosidic bond, so it is a non-reducing sugar.

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Vitamin

A vitamin is an organic compound required as a nutrient in tiny amounts by an organism. A compound is called a vitamin when it cannot be synthesized in sufficient quantities by an organism, and must be obtained from the diet. Thus, the term is conditional both on the circumstances and the particular organism. For example, ascorbic acid functions as vitamin C for some animals but not others, and vitamins D and K are required in the human diet only in certain circumstances. Vitamins are classified by their biological and chemical activity, not their structure. Thus, each "vitamin" may refer to several vitamer compounds that all show the biological activity associated with a particular vitamin. Such a set of chemicals are grouped under an alphabetized vitamin "generic descriptor" title, such as "vitamin A," which includes the compounds retinal, retinol, and many carotenoids. Vitamers are often inter-converted in the body. The term vitamin does not include other essential nutrients such as dietary minerals, essential fatty acids, or essential amino acids, nor does it encompass the large number of other nutrients that promote health but are otherwise required less often. Vitamins have diverse biochemical functions, including function as hormones (e.g. vitamin D), antioxidants (e.g. vitamin E), and mediators of cell signaling and regulators of cell and tissue growth and differentiation (e.g. vitamin A). The largest number of vitamins (e.g. B complex vitamins) function as precursors for enzyme cofactor bio-molecules (coenzymes), that help act as catalysts and substrates in metabolism. When acting as part of a catalyst, vitamins are bound to enzymes and are called prosthetic groups. For example, biotin is part of enzymes involved in making fatty acids. Vitamins also act as coenzymes to carry chemical groups between enzymes. For example, folic acid carries various forms of carbon group – methyl, formyl and methylene - in the cell. Although these roles in assisting enzyme reactions are vitamins' best-known function, the other vitamin functions are equally important.

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The benefits of Microbiology

Use of bacteria as probiotics and pre-biotics

Probiotics' refers to useful, live bacteria consumed in small amounts for their potential benefits on health. Pre-biotics refer to certain substances which are consumed in order to promote the growth of commensal bacteria in the body with the aim of obtaining increased benefits on human health. Commensal bacteria or friendly bacteria present in out intestines can help in the process of digestion. In the United States, the probiotic bacteria are available in form of conventional dairy foods supplemented with these bacteria or as dietary supplements in the form of capsules, powder or tablets .A special branch of microbiology deals with study and manufacture of such pro-biotic and pre-biotic bacteria.

Vitamin synthesis

Bacteria like E.coli present in human colon are involved in synthesis of vitamins like vitamin B12, folic acid, biotin and K, which may be used by the host. Such bacteria are often used for commercial preparation of vitamins like riboflavin.

Use of bacteria in dairy and food industry

Bacteria, especially the lactic acid producing lactobacillus are specially used in preparation of food stuffs involving the process of fermentation e.g. yogurts, cheese, breads, fermented soy sauces, pickles, soy sauces etc.

Use of Microbiology in Agriculture and farming

Symbiotically associated bacteria are able to biologically convert nitrogen gas present in the atmosphere into ammonia which helps in enriching the soil and promotes optimal growth of plants. Such bacteria are useful in the areas of agriculture and farming and increasing crop yield without use of chemical fertilizers. Bacteria are also important for production of compost which is decayed ganic matter and serves as a rich source of nutrition for the plants.

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Microbiology and Types of Microbiology

Microbiology is the study of microorganisms, which are unicellular or cell-cluster microscopic organisms. This includes eukaryote such as fungi and protists, and prokaryotes, which are bacteria and archaea. Viruses, though not strictly classed as living organisms, are also studied. In short; microbiology refers to the study of life and organisms that are too small to be seen with the naked eye. Microbiology is a broad term which includes virology, mycology, parasitology, bacteriology and other branches. A microbiologist is a specialist in microbiology. Microbiology is researched actively, and the field is advancing continually. We have probably only studied about one percent of all of the microbe species on Earth. Although microbes were first observed over three hundred years ago, the field of microbiology can be said to be in its infancy relative to older biological disciplines such as zoology and botany.

Types and the field of microbiology can be generally divided into several subdisciplines:

* Microbial physiology: The study of how the microbial cell functions biochemically. Includes the study of microbial growth, microbial metabolism and microbial cell structure.

* Microbial genetics: The study of how genes are organised and regulated in microbes in relation to their cellular functions. Closely related to the field of molecular biology.

* Medical microbiology: The study of the pathogenic microbes and the role of microbes in human illness. Includes the study of microbial pathogenesis and epidemiology and is related to the study of disease pathology and immunology.

* Veterinary microbiology: The study of the role in microbes in veterinary medicine or animal taxonomy.

* Environmental microbiology: The study of the function and diversity of microbes in their natural environments. Includes the study of microbial ecology, microbially-mediated nutrient cycling, geomicrobiology, microbial diversity and bioremediation. Characterisation of key bacterial habitats such as the rhizosphere and phyllosphere, soil and groundwater ecosystems, open oceans or extreme environments (extremophiles).

* Evolutionary microbiology: The study of the evolution of microbes. Includes the study of bacterial systematics and taxonomy.

* Industrial microbiology: The exploitation of microbes for use in industrial processes. Examples include industrial fermentation and wastewater treatment. Closely linked to the biotechnology industry. This field also includes brewing, an important application of microbiology.

* Aeromicrobiology: The study of airborne microorganisms.

* Food microbiology: The study of microorganisms causing food spoilage and foodborne illness. Using microorganisms to produce foods, for example by fermentation.

* Pharmaceutical microbiology: the study of microorganisms causing pharmaceutical contamination and spoilage.

* Oral microbiology: the study of microorganisms of the mouth in particular those causing caries and periodontal disease.

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Uses of Genetic Testing

Diagnostic testing Diagnostic testing is used to identify or confirm the diagnosis of a disease or condition in a person or a family. Diagnostic testing gives a "yes" or "no" answer in most cases. It is sometimes helpful in determining the course of a disease and the choice of treatment. Examples of diagnostic testing include chromosome studies, direct DNA studies, and biochemical genetic testing. Predictive genetic testing Predictive genetic testing determines the chances that a healthy individual with or without a family history of a certain disease might develop that disease. There is predictive testing available for some adult-onset conditions (those diseases which manifest themselves in adulthood) such as some types of cancer, cardiovascular disease, and some single gene disorders.

Presymptomatic genetic testing Presymptomatic genetic testing is used to determine whether persons who have a family history of a disease, but no current symptoms, have the gene alterations associated with the disease. Carrier testing Carrier testing is performed to determine whether a person carries one copy of an altered gene for a particular disease. The disease may be autosomal recessive, which means that the disease is present in an individual only if two copies of the altered gene are inherited. Couples who both carry the same autosomal recessive gene have a one in four, or 25 percent, chance with each pregnancy to have a child with that disease. A recessive disease may also be X-linked recessive, which means that the altered gene is located on the X chromosome. Since females have two X chromosomes, and males have one X and one Y chromosome, females can be carriers of a gene on the X but are not affected (provided the other X has the normal copy of the gene). On the other hand, males are usually affected with the disease, if they have the altered gene on their X chromosome (because they do not possess the normal copy of the gene on the Y chromosome). Therefore, "carrier testing" for X-linked conditions is usually done in females. Prenatal diagnosis Prenatal diagnosis is used to diagnose a genetic disease or condition in the developing fetus and includes maternal serum screening, ultrasound (sonograms), amniocentesis, chorionic villus sampling (CVS), and percutaneous umbilical blood sampling (PUBS). Preimplantation studies Preimplantation studies are used following in vitro fertilization to diagnose a genetic disease or condition in an embryo before it is implanted into the mother's uterus.

Newborn screening Newborn screening is performed in newborns in state public health programs to detect certain genetic diseases for which early diagnosis and treatment are available..

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DNA virus

A DNA virus is a virus that has DNA as its genetic material and replicates using a DNA-dependent DNA polymerase. The nucleic acid is usually double-stranded DNA (dsDNA) but may also be single-stranded DNA (ssDNA). DNA viruses belong to either Group I or Group II of the Baltimore classification system for viruses. Single-stranded DNA is usually expanded to double-stranded in infected cells. Although Group VII viruses such as hepatitis B contain a DNA genome, they are not considered DNA viruses according to the Baltimore classification, but rather reverse transcribing viruses because they replicate through an RNA intermediate,

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Virus

A virus (from the Latin virus meaning toxin or poison) is a sub-microscopic infectious agent that is unable to grow or reproduce outside a host cell. Viruses infect all cellular life. The first known virus, tobacco mosaic virus, was discovered by Martinus Beijerinck in 1899, and now more than 5,000 types of virus have been described. The study of viruses is known as virology, and is a branch of microbiology.

Viruses consist of two or three parts: all viruses have genes made from either DNA or RNA, long molecules that carry genetic information; all have a protein coat that protects these genes; and some have an envelope of fat that surrounds them when they are outside a cell. Viruses vary in shape from simple helical and icosahedral shapes, to more complex structures. They are about 100 times smaller than bacteria. The origins of viruses are unclear: some may have evolved from plasmids—pieces of DNA that can move between cells—others may have evolved from bacteria.

Viruses spread in many ways; different species of virus use different methods. For example, plant viruses are often transmitted from plant to plant by insects that feed on sap, such as aphids, while animal viruses can be carried by blood-sucking insects. These disease-bearing organisms are known as vectors. Influenza viruses are spread by coughing and sneezing, and others such as norovirus, are transmitted by the faecal-oral route, when they contaminate hands, food or water. Rotavirus is often spread by direct contact with infected children. HIV is one of several viruses that are transmitted through sex.

Not all viruses cause disease, as many viruses reproduce without causing any obvious harm to the infected organism. Some viruses such as HIV can causelife-long or chronic infections, and the viruses continue to replicate in the body despite the hosts' defence mechanisms. However, viral infections in animals usually cause an immune response, which can completely eliminate a virus. These immune responses can also be produced by vaccines that give lifelong immunity to a viral infection. Microorganisms such as bacteria also have defences against viral infection, such as restriction modification systems. Antibiotics have no effect on viruses, but antiviral drugs have been developed to treat life-threatening and more minor infections.

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