Contains DNA pentose sugar

Encounters with nature 8, textbook

The structure of DNA DNA molecules are giant molecules made up of thousands of nucleotides. DNA nucleotides consist of the pentose deoxyribose, an organic base (guanine, cytosine, adenine, thymine) attached to the first carbon atom of sugar (C 1) and a phosphate group attached to the fifth carbon atom of the sugar molecule (C 5) is (see Fig. 4a). The individual nucleotides are linked to form chains via the phosphate group and the OH group of the sugar on the third carbon atom (C 3) with elimination of water. As can be seen in Fig. 4c, the nucleotide chains thus have one end with an OH group, the so-called 3‘ end, and one with a phosphate residue (5‘ end). In each case two nucleotide chains are connected in opposite directions (antiparallel) via the bases (via hydrogen bonds) like a rope ladder to form a double strand. The molecular structure of the bases only enables bonds between adenine and thymine, guanine and cytosine (specific base pairing). The double strand is spirally wound, it is referred to as a double helix (see Fig. 4b). Giant molecules very long chain-like molecules nucleotides building blocks of nucleic acids (deoxyribo nucleic acid DNA and ribonucleic acid RNA) pentose sugar, whose carbon backbone contains five carbon atoms specific base pairing adenine and thymine form two hydrogen bonds, guanine and cytosine three hydrogen bonds. Double helix helix (Greek) = twist The structure of DNA A… adenine T… thymine G… guanine C… cytosine P… phosphate group Z… sugar a) b) c) 4 DNA structure. a) nucleotide b) double helix c) structure of a section of a DNA chain workbook pages 10, 11, 17, 19 M 3 James D. Watson and Francis Crick 21 For testing purposes only - property of the publisher öbv

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