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- 2. Nucleotides Nucleotides arethe monomers of nucleic acids They are energy rich compounds They provide energy for metabolic processes They are a part of enzyme cofactors e.g. They are a part of enzyme cofactors e.g. NAD - nicotinamide adenine dinucleotide, FAD – flavin adenine dinucleotide They act as secondary chemical messengers in response to hormones
- 3. Nucleotides A nucleotideconsist of three portions (a) a nitrogenous bases – purine and pyrimidine common purine bases – adenine and guanine common pyrimidine bases – cytosine, uracil, thymine common pyrimidine bases – cytosine, uracil, thymine http://www.uic.edu/classes/bios/bios100/lecturesf04am/nucleotides.jpg Uracil
- 4. Nucleotides (b) A sugar– deoxyribose or ribose http://www.mun.ca/biology/scarr/Deoxyribose_vs_Ribose.gif
- 5. Nucleotides (c) Oneor more phosphate groups
- 6. Nucleotides Some commonnucleotides include- ATP – adenosine triphosphate ADP – adenosine diphosphate AMP – adenosine monophosphate AMP – adenosine monophosphate GTP – guanosine triphosphate UTP – uridine triphosphate CTP – cytidine triphosphate
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- 10. Nucleic Acids Thereare two types of nucleic acids (a) DNA – deoxyribonucleic acid (b) RNA – ribonucleic acid They provide genetic information They provide genetic information Both nucleic acids are found in plants and animals Viruses contain either RNA or DNA but not both
- 11. Nucleic Acids -DNA It is found in the chromatin of the cell nucleolus It is also found outside the nucleus i.e. in the mitochondria and chloroplast It contains genetic information in a segment called the genes It contains information (blue print) that is used to construct other cell components It contains information (blue print) that is used to construct other cell components The DNA structure consist of two strands that are entwined It is made up of nucleotide monomers The structure is described as a double helix (proposed by Watson and Crick) The helix is formed through the pairing of the nitrogenous bases in the nucleotide
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- 13. Nucleic Acids -DNA The double helix is also called the B-form DNA or B-DNA This form is very stable There also exists different variations in DNA helix structure i.e. A-DNA and Z- DNA DNA Both forms are converted into the B-DNA at normal physiological conditions
- 14. Main Differences inVariations A-DNA B-DNA Z-DNA Right handed helix Right handed helix Left handed helix Helix has a hollow core Helix has a solid core Helix has a solid core – more tightly packed Appears when the DNA is dehydrated Occurs at normal physiological conditions Occurs when there is very high salt concentration
- 15. Nucleic Acids –DNA Structure The backbone of the DNA is comprised of a deoxyribose sugar linked by phosphodiester bridges The 3' hydroxyl group of the sugar is linked to the 5' hydroxyl group of another sugar by a phosphodiester bond 5' hydroxyl group of another sugar by a phosphodiester bond The linking of the sugars maintains the structure of the DNA
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- 17. Nucleic Acids –DNA Structure The strands run antiparallel to each other, i.e. one strands run in the 3' → 5' direction and the other strand runs in the 5' → 3' direction The nitrogenous bases found in DNA are adenine (A), thymine (T), cytosine (C) and guanine (G) guanine (G) They carry the genetic information Adenine is paired with thymine and vice versa by 2 hydrogen bonds A =T Guanine is paired with cytosine by 3 hydrogen bonds (G ≡ C)
- 18. Nucleic Acids –DNA Structure The pairing of the bases is referred to as complementary base pairing The two helices are The two helices are complementary to each other. They are not identical There must exist equal amounts of complementary bases http://upload.wikimedia.org/wikipedia/commons/thumb/e/e4/DNA_chemical _structure.svg/350px-DNA_chemical_structure.svg.png
- 19. Nucleic Acids –DNA Structure The DNA helix can be bent or super coiled This flexibility allows DNA to be wrapped around proteins Allows the DNA to be compact into smaller volumes
- 20. Nucleic Acids -RNA RNA is present in the cytosol of the cell and in the nucleolus It is formed from DNA by a process called Transcription The molecule consist of (a) a phosphate group (a) a phosphate group (b) a nitrogenous base – adenine (A), uracil (U), cytosine (C) and guanine (G) (c) sugar – ribose
- 21. Nucleic Acids -RNA Similar to DNA, the nitrogenous bases in RNA carries the genetic information and sugar-phosphate serves to maintain the structure of the molecule
- 22. Nucleic Acids –RNA Structure The structure is single stranded and runs in the 5' → 3' direction However because base pairing can occur, the molecule can fold on itself in the form of a hairpin During base pairing adenine pairs with uracil and guanine with cytosine During base pairing adenine pairs with uracil and guanine with cytosine A = U G ≡ C The hairpin formation does not require the molecule to have equal amounts of complementary base pairs
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- 25. Differences Between DNAand RNA
- 26. DNA RNA Found inthe chromatin of the nucleus Found mainly in the cytoplasm and to a lesser extent in the nucleolus Helix is B form; Protected in the nucleus and is tightly packed Helix is A form; They are continually made, broken down and reuse Sugar – 2 deoxyribose (more stable sugar) Sugar – ribose Nitrogenous bases are A, T, C and G Nitrogenous bases are A, U, C and G Double stranded Normally single stranded Double stranded Normally single stranded The A/T and G/C ratio is 1 Complementary base pairs ratio not necessary Base pairing occurs throughout the molecule Base pairing occurs at specific locations Stores genetic information Transfer of genetic information needed for protein synthesis Self replicating Must be synthesized from DNA molecule Can be damaged by UV rays More resistant to damage by UV rays
- 27. Types of RNA There exist three RNA forms ribosomal RNA – rRNA transfer RNA – tRNA messenger RNA – mRNA messenger RNA – mRNA They differ from each other by size, function and stability
- 28. Types of RNA- rRNA It is the most abundant and makes up 80% of the RNA in the cells It is also the most stable form The molecule has a higher GC The molecule has a higher GC content than AU content In the cytoplasm rRNA combines with proteins to form ribosomes
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- 30. Types of RNA- tRNA It occupies 15% of the total RNA in the cell It is the smallest polymeric form It functions as a carrier of activated amino acids to a growing polypeptide chain (protein synthesis) (protein synthesis) It binds to specific amino acids All tRNA molecules have a three fold clover leaf configuration The 3' end contains the CCA sequence. Amino acids bind to this end via esterification The anticodon region base pairs to the corresponding codon region on the mRNA molecule Each tRNA molecule contains a specific anticodon triplet
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- 32. Types of RNA- mRNA Otherwise called template RNA Comprises 5% of RNA in the cell It is synthesized on the surface of the DNA template It carries genetic information from the nuclear DNA to the cytosol It carries genetic information from the nuclear DNA to the cytosol It is used as a template for protein synthesis If the mRNA carries the code for a simple protein it is called monocistronic If it carries the code for more than one kind of protein it is polycistronic