Biology Bonds

polar and nonpolar covalent bonds

within molecules, STRONG; atoms share electron pairs, polar covalent bonds share electrons unequally; nonpolar covalent bonds share them more equally. polarity along does NOT determine bond strength

ionic bonds or interactions

within ionic solids or between charged groups; strong without water; weaker in water; opposite charges attract. water molecules and dissolved ions shield the charges, so ionic interactions are usually weakened in cells and other aqueous environments

hydrogen bonds

within/between molecules; moderate individually strength; partially positive hydrogen attracted to electronegative atom, commonly oxygen or nitrogen. hydrogen bonds help stabilize water, DNA, proteins and molecular recognition

hydrophilic interactions

between polar or charged groups and water; variable strength; not one specific type of bond; they include hydrogen bonds, ion-dipole attractions, dipole-dipole attractions that favor contact with water

hydrophobic interactions

between nonpolar regions in water; weak individually bonds, strong collectively. not true bonds. nonpolar groups cluster to reduce their exposed surface area in water, increasing the freedom of surrounding water molecules. interactions are important in membranes and protein folding

van der Waals forces

between atoms in close contact, within or between molecules; very weak individually bonds; short-range attractions from temporary or permanent dipoles. LDFS present between all atoms and molecules. many close contacts can provide substantial collective stabilization