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|موضوع: Nucleic Acids الإثنين يونيو 22, 2015 12:04 am|| |
الموضوع الاصلي : Nucleic Acids المصدر : مستشفى الرفاعي العام
بسم الله الرحمن الرحيم
The two types of nucleic acids are DNA (deoxyribonucleic acid) and RNA (ribonucleic acid)
• Nucleic acids are macromolecules composed of nucleotides.
Nucleotides are composed of a sugar, a base, and a phosphate. DNA and RNA are polymers of nucleotides.
• DNA contains the sugar deoxyribose; contains the bases adenine, guanine, thymine, and cytosine; is double-stranded; and forms a helix.
• RNA contains the sugar ribose; contains the bases adenine, guanine, uracil, and cytosine; and does not form a helix.
In addition to being the subunits of nucleic acids, nucleotides have metabolic functions. When adenosine (adenine plus ribose) is modified by the addition of three phosphate groups instead of one, it becomes ATP (adenosine triphosphate), which is an energy carrier in cells.
ATP is a high-energy molecule because its bonds are unstable.
• ATP undergoes hydrolysis to ADP + P , which releases energy used by cells to do metabolic work.