Pathogens Bio Molecules And Dna

BIOMOLECULES „

Pathogens Biomolecules and DNA B.K.Kolita Kamal Jinadasa, Jinadasa, Post Harvest Technology Division, NARA, ColomboColombo-15, Sri Lanka.

All organims are made of biomolecules. biomolecules.

A biomolecule is a chemical compound that naturally occurs in living organisms. Biomolecules consist primarily of carbon and hydrogen, hydrogen, along with nitrogen, nitrogen, oxygen, oxygen, phosphorus and sulfur. sulfur. Other elements sometimes are incorporated but are much less common.

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The most important biomolecules are: 1. Lipids and derivates like Phospholipid, Phospholipid, Glycolipid, Glycolipid, Sterol. Sterol. 2. Peptide and derivates like Oligopeptide, Oligopeptide, Polypeptide and Protein. Protein. 3. Oligosaccharide, Oligosaccharide, Polysaccharide . 4. Nucleic acid,: acid,: DNA, DNA, RNA. RNA.

NUCLEIC ACIDS „

A nucleic acid is a complex, highhigh-molecularmolecular-weight biochemical macromolecule composed of nucleotide chains that convey genetic information. information. The most common nucleic acids are deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). Nucleic acids are found in all living cells and viruses. viruses.

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The monomers from which nucleic acids are constructed are called nucleotides. nucleotides. Each nucleotide consists of three components: a nitrogenous heterocyclic base, base, either a purine or a pyrimidine; pyrimidine; a pentose sugar; sugar; and a phosphate group.

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Different nucleic acid types differ in the structure of the sugar sugar in their nucleotides; DNA contains 22-deoxyriboses while RNA contains ribose. ribose. The nitrogenous bases found in the two nucleic acids are different: adenine, adenine, cytosine, cytosine, and guanine are in both RNA and DNA, while thymine only occurs in DNA and uracil only occurs in RNA.

Nucleotide structure

Ribonucleic acid (RNA) „

RNA polynucleotides contain ribose sugars and predominantly uracil. uracil.

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RNA serves as the template for translation of genes into proteins, proteins, transferring amino acids to the ribosome to form proteins, and also translating the transcript into proteins.

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Types of RNA

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Messenger RNA (mRNA): Messenger RNA is RNA that carries information from DNA to the ribosome sites of protein synthesis in the cell. Once mRNA has been transcribed from DNA, it is exported from the nucleus into the cytoplasm.

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Transfer RNA (tRNA (tRNA)) : Transfer RNA is a small RNA chain of about 7474-95 nucleotides that transfers a specific amino acid to a growing polypeptide chain at the ribosomal site of protein synthesis during translation. translation. It has sites for aminoamino-acid attachment and an anticodon region for codon recognition that binds to a specific sequence on the messenger RNA chain through hydrogen bonding. It is a type of nonnon-coding RNA. RNA.

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Ribosomal RNA (rRNA (rRNA)) : Ribosomal RNA is a component of the ribosomes, ribosomes, the protein synthetic factories in the cell. Eukaryotic ribosomes contain four different rRNA molecules: 18S, 5.8S, 28S, and 5S rRNA. rRNA. The ribosome binds mRNA and carries out protein synthesis.

RNA Transfer RNA (tRNA (tRNA))

Messenger RNA

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DNA

RNA

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Deoxyribonucleic acid (DNA) DNA) is a nucleic acid that contains the genetic instructions for the development and functioning of living organisms In eukaryotes such as animals and plants, plants, DNA is stored inside the cell nucleus, nucleus, while in prokaryotes such as bacteria, bacteria, the DNA is in the cell's cytoplasm. cytoplasm. EUKARYOTE

PROKARYOTE

Ribosomic RNA

DNA BONDS

DOUBLE HELIX

The DNA double helix is stabilized by hydrogen bonds between the bases attached to the two strands. strands. The four bases found in DNA are adenine (abbreviated A), cytosine (C), guanine (G) and thymine (T).

BASES

Base pairing

These bases are classified into two types; types; adenine and guanine are fused fivefive- and sixsixmembered heterocyclic compounds called purines, purines, while cytosine and thymine are sixsixmembered rings called pyrimidines Each type of base on one strand forms a bond with just one type of base on the other strand. strand. This is called complementary base pairin. pairin. Purines form hydrogen bonds to pyrimidines, pyrimidines, with A bonding only to T, and C bonding only to G.

GC base pair with three hydrogen bonds

Adenine

Guanine

Cytosine

AT base pair with two hydrogen bonds

Thymine

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Double helix •DNA is a long polymer made from repeating units called nucleotides. nucleotides. •A nucleotide is a chemical compound that consists of 3 components: components: a heterocyclic base, base, a sugar, sugar, and one or more phosphate groups. groups.

Antiparallel strands DNA is antiparallel, antiparallel, it means that the two strands of DNA have opposite chemical polarity, or, stated another way, their sugarsugar-phosphate backbones run in opposite directions

•These two long strands entwine like vines, in the shape of a double helix. helix.

DNA „

These bases are classified into two types; types; adenine and guanine are fused fivefiveand sixsix-membered heterocyclic compounds called purines, purines, while cytosine and thymine are sixsix-membered rings called pyrimidines

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Each type of base on one strand forms a bond with just one type of base on the other strand. strand. This is called complementary base pairin. pairin. Purines form hydrogen bonds to pyrimidines, pyrimidines, with A bonding only to T, and C bonding only to G.

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DNA exists in several possible conformations. conformations. The conformations so far identified are: A-DNA, DNA, BB-DNA, CC-DNA, DD-DNA, EE-DNA, HH-DNA, LLDNA, and Z-DNA. DNA.

DNA special properties „

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DNA is made of two antiparallel and complimentary strands : Direction in nucleic acids is specified by referring to the carbons of the ribose ribose ring in the sugarsugar-phosphate backbone of DNA. 5' specifies the 5th carbon in the ribose ring, counting clockwise from the oxygen molecule, and 3' specifies the 3rd carbon in the ring. Nucleic acid polymerization cannot occur occur in 3' to 5', because of the difference in chemical properties between the 5' methyl group and the 3' ringring-carbon with an attached hydroxyl group. Hydrophillic polar external sugarsugar-phosphate backbone. Hydrophobic core of bases: Adenine, Thymine, Guanine, Cytosine. DNA is negatively charged due to the phosphate ions present in the the riboseribosephosphate backbone. It moves towards the positive pole during electrophoresis. DNA resist high temperatures. When DNA is desnatured DNA, it can renature itself. This property is very important in PCR and permit the primer annealing.

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