Lesson 8 of 14 · 6 min
Nucleic acids
NCERT §9.6
Kabir sends Farah a picture of a DNA model and asks her to find the three repeating parts of every rung. She finds the bases first.
The lesson in notes
In short
Nucleic acids, the remaining macromolecule of the acid-insoluble fraction, are polynucleotides.
Polysaccharides, polypeptides and polynucleotides together make up the true macromolecular fraction of a tissue or cell.
The building block is the nucleotide, with three chemically distinct parts: a heterocyclic compound (the nitrogen base), a monosaccharide (the sugar) and phosphoric acid (phosphate).
Five bases occur: adenine, guanine, cytosine, thymine and uracil. Of these, adenine and guanine are substituted purines, and the other three are substituted pyrimidines.
The sugar is either ribose or 2' deoxyribose, both pentoses. A nucleic acid with deoxyribose is deoxyribonucleic acid (DNA); one with ribose is ribonucleic acid (RNA).