polarity 1.
1. As applied to a molecular bond between two atoms, the term polarity refers to a state in which the electrons in the bond are localized more to one atom than the other, giving that atom a partial negative charge (the other atom is partially positively charged). The presence of polar bonds confers a number of impor- tant chemical properties to the compound that contains them, including solubility in water. 2. As applied to cell microanatomy, polarity refers to specialization of the cell architecture at different parts of the cell, for example, the presence of cilia and secretory vesicles located at the apical, as opposed to the basal, end of the epithelial cells lining the gut and respiratory tracts. 3. As applied to nucleic-acid strands, the term refers to the fact that the two ends of any nucleic-acid strand are distinguishable from one another by whether the end is 5′ or 3′. This gives the strand a directionality or polarity.