List and define major chemical bonds used to connect biological molecules

Ionic boning involves a transfer of an electron, so one atom gains an electron while one atom loses an electron. One of the resulting ions carries a negative charge (anion), and the other ion carries a positive charge (cation). Because opposite charges attract, the atoms bond together to form a molecule.
The most common bond in organic molecules, a covalent bond involves the sharing of electrons between two atoms. The pair of shared electrons forms a new orbit that extends around the nuclei of both atoms, producing a molecule. There are two secondary types of covalent bonds that are relevant to biology — polar bonds and hydrogen bonds.
Two atoms connected by a covalent bond may exert different attractions for the electrons in the bond, producing an unevenly distributed charge. The result is known as a polar bond, an intermediate case between ionic and covalent bonding, with one end of the molecule slightly negatively charged and the other end slightly positively charged.
Because they’re polarized, two adjacent H2O (water) molecules can form a linkage known as a hydrogen bond, where the (electronegative) hydrogen atom of one H2O molecule is electrostatically attracted to the (electropositive) oxygen atom of an adjacent water molecule.