BIOB10H3 Lecture : chp2 notes.docx
Document Summary
Pair of electrons are shared between pair of atoms. For example, atoms joined by a single bond are able to rotate relative to one another, whereas the atoms of double (and triple) bonds lack this ability. Molecules, such as water, that have an asymmetric distribution of charge (or dipole) are referred to as polar molecules. Noncovalent bonds do not depend on shared electrons but rather on attractive forces between atoms having an opposite charge. Individual noncovalent bonds are weak (about 1 to 5 kcal/mol) and are thus readily broken and reformed. Because of their ability to interact with water, polar molecules, such as sugars and amino acids (described shortly), are said to be hydrophilic, or water loving . When nonpolar compounds are mixed with water, the nonpolar, hydrophobic ( water fearing ) molecules are forced into aggregates, which minimizes their exposure to the polar surroundings. A molecule that is capable of releasing (donating) a hydrogen ion is termed an acid.
