Physiology
Plant physiology encompasses the entire range of chemical reactions carried out by plants. Like other living organisms, plants use deoxyribonucleic acid (DNA) to store genetic information and proteins to carry out cellular functions. Enzymes regulate both anabolism (buildup of complex macromolecules) and catabolism (the breaking down of macromolecules into simple molecules). Unlike animals, plants create a large variety of secondary metabolites, complex molecules with a range of specialized functions.
Structure and Function of Macromolecules
Dna.
Deoxyribonucleic acid (DNA) is a high-molecular-weight polymer, containing phosphate, four nitrogen bases, and the pentose sugar deoxyri-bose. There are two pyrimidine bases, cytosine and thymine, and two purine bases, adenine and guanine. These nitrogen bases are joined to long chains of alternating sugar and phosphate. The three-dimensional structure of DNA consists of a two-stranded alpha-helix with each strand consisting of a long chain of polynucleotides and the strands joined through the bases by hydrogen bonding. The two strands are precisely complementary in their base sequence, since adenine in one chain is always paired with thymine on the other (and vice versa) and, similarly, guanine is always paired with cytosine (see the accompanying figure of the structure of DNA).
DNA occurs in the chromosomal material of the nucleus, closely associated with proteins called histones.
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