University:
York University
Course:
SC/BIOL 2021 | Cell Biology
Academic year:

2023
Views:

406

Pages:

2
Author:

Nick T.

Covalent Bonds: Bond strength: Amount of energy needed to break the bond (kcal/mole or kJ/mole) Normally only broken during specific reactions or using enzymes in living things Ionic Bonds: Formed by the gain and loss of electrons Both atoms become charged ions: Cation: Positive charge, loses e- Anion: Negative charge, accepts e- Salts: Ions held together by only ionic bonds Many are highly water soluble 10-100x weaker in aqueous solutions Example: NaCl Hydrogen Bonds: Water is 70% of the cell's weight H gains charge, O gains charge Electrical attraction causes hydrogen bonds Much weaker than covalent bonds, easily broken Can also be formed with a H atom in a polar covalent linkage when close to O atoms Typically N and O Weak Interactions Bringing Molecules Together: Non-covalent bonds (0) Individually weak, but their energies in sums create an effective force between molecules Electrostatic Attraction: Ionic bonds in a salt crystal Strongest with fully charged atoms (e.g., Na+, Cl-) Weaker bond with polar covalently bonded molecules Important in biology Example: Any large molecule with polar groups has a pattern of partial charges on its surface. When this molecule encounters another with a complementary set of charges, the two will be drawn to each other by electrostatic attraction. Van der Waals Attraction: When any two atoms approach each other closely Caused by fluctuations in electron distribution Relative length and strength compared to covalent bonds Occurs in every type of molecule Hydrophobic Force: Pushing of non-polar surfaces out of the hydrogen-bonded water network Promotes molecular interactions Example: Building cell membranes