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0:05 Nucleic acids are a class of biomolecules that are found in all living organisms
0:11 and are responsible for the storage of genetic information.
0:14 They are also responsible for protein synthesis.
0:18 Nucleic acids are made up of monomers called nucleotides.
0:22 Nucleotides are made up of three components: a 5 carbon sugar such as ribose,
0:29 a phosphate functional group, and a nitrogenous base.
0:34 The 5 carbon sugar present in DNA is deoxyribose
0:38 and the four nitrogenous bases are adenine, guanine, cytosine and thymine.
0:45 Nucleotides are linked together by dehydration synthesis,
0:49 or polymerization reactions, between the sugar of one nucleotide
0:54 and the phosphate group of a second nucleotide.
0:57 In the process, a sugar – phosphate backbone is formed,
1:01 linking the nucleotides together. Notice how the nitrogenous bases
1:05 project to one side of the backbone.
1:08 DNA is composed of two strands arranged as a right-handed helix.
1:13 The strands are also anti-parallel, meaning that they are orientated in opposite directions.
1:19 The two strands are held together by hydrogen bonds. Guanine forms hydrogen bonds with cytosine
1:26 and adenine bonds with thymine. This complementary base pairing links the strands together.
1:32 It also plays an important role in the replication of the DNA molecule.
1:37 RNA differs from DNA in that it contains the sugar ribose
1:42 instead of deoxyribose and the nitrogenous base uracil instead of thymine.
1:47 Also RNA is usually single stranded and does not typically form a helix.
1:53 Because of this, it is less stable than DNA and is usually more temporary.
1:59 While DNA stores the information that is needed to construct a protein,
2:04 RNA functions in regulating the expression of this information
2:08 in the protein synthesis process.
2:11 Not all nucleic acids are involved in information processing in the cell.
2:16 ATP (adenosine tri-phosphate) is a modified nucleotide that plays a central role in
2:23 energy processing within cells. ATP is composed of the nitrogenous base, adenine,
2:29 bound to the sugar ribose just like in RNA.
2:32 However three phosphate groups can be added to the molecule.
2:36 The bonds between the phosphate groups are high energy bonds.
2:40 These molecules serve as temporary energy batteries for the cell.
2:45 When energy is needed, the terminal phosphate group is removed,
2:50 releasing energy and forming adenosine diphosphate,
2:54 which may then be recharged by the energy pathways of the cell.
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