A nucleotide consists of a 5-carbon sugar (S), a phosphate group (P), and an organic base (B).

Figure 2.20

A schematic representation of a polynucleotide chain. A nucleic acid molecule consists of (a) one (RNA) or (b) two (DNA) polynucleotide chains.

it is a single polynucleotide chain. The nucleotides of the second type contain deoxyribose sugar; nucleic acid of this type is called DNA (deoxyribonucleic acid), and it is a double polynucleotide chain. Figure 2.21 compares the structure of ribose and deoxyribose, which differ by one oxygen atom. DNA and RNA also differ in the types of bases they contain.

DNA molecules store information in a type of molecular code. Cells use this information to construct spe-

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Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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