Intro: The role of nucleic acids. DNA and RNA are known as the nucleic acids. They are acidic molecules DNA is responsible for storing information of the genetic characteristics of an organisms RNA enables the information stored in DNA to be expressed In carrying out its functions, DNA needs to have: i. Stable molecule ii. Contain some ‘code’ iii. Must be able to replicate
B 8.1: Describe the structure of nucleotides and their condensation polymers (nucleic acids or polynucleotide). DNA & RNA = polymers Built from monomers known as nucleotides, so it is polynucleotide
A. Nucleotides are the building blocks of nucleic acids Nucleotides is made up of 3 components: i. Pentose sugar: C5H10O5 (DNA = deoxyribose, RNA= ribose)
Adenine, guanine, cytosine = found in DNA & RNA Thymine = exclusively in DNA Uracil = exclusively in RNA Ribonucleotides are found in RNA: contain ribose sugar and either A, G, C or U. Deoxyribonucleotides are found in DNA: deoxyribose sugar and either A, G, C or T.
B. Nucleotides condense to form polynuleotides Nucleotides link together in condensation reaction involving the phosphate at the 5’ position of one nucleotide and the –OH group at the 3’ position of the next nucleotide.
Phosphodiester linkage*nitrogenous bases do not take part in the polymerization of the nucleotides but remain attached to C1
C. DNA is a double helix of two polynucleotides 2 polynucleotide strand are coiled around the same axis forming a double helix with sugar-phosphate backbone on the outside and the nitrogeneous bases on the inside.
10 nucleotides = one complete turn of the helix with length of 3.4 nm The 2 polynucleotides strands are anti-parallel(3’ 5’ and 5’ 3’) Base pairing: A=T , G C
D. RNA is a single-stranded polynucleotide molecules RNA differs from DNA: - Ribose sugar instead of deoxyribose - The base uracil instead of thymine - A single stranded structure - Less stable than DNA - Short-lived in the cells - RNA is able to cross the nuclear membrane
• 3 different RNA exist in human:- Messenger RNA (mRNA)- Transfer RNA (tRNA)- Ribosomal RNA (rRNA)*RNA polynucleotide is able to carries information in its sequence of bases