Lecture 2 Properties of Biological Molecules Flashcards
Covalent Bond
Very strong, considerable energy must be expended to break them
Ex. Typical carbon-carbon (C-C) has bond length of 1.54A and bond E of 85 kcal/mol
C-C bond
Covalent bond
Bond length 1.54Angstrom
Bond E kcal/mol
Covalent and non-covalent bonds are important for
The structure and stability of biological molecules
3 types of Non-Covalent Bond
- Electrostatic interactions
- Hydrogen bonds
- van der Waals interactions
Electrostatic Interactions
(less strong than covalent bonds, but strongest of non-covalent)
A charged group on one molecule can attract an oppositely charged group on another molecule.
Defined by Coulomb’s Law
Amount of energy required to break electrostatic interactions
Variable, 1.4-55kcal/mol
Hydrogen bonds
Similar to electrostatic, less E
linear
These interactions are fundamentally electrostatic interactions
Bond E is 1-5kcal/mol
Bond length is 3 Angrstrom (depending on distance D)
van der Waals Interactions
Has cloud of e' around it, variable very weak, breakable Signal transduction The basis of a van der Waals interaction is that the distribution of electronic charge around an atom fluctuates with time Bond E is 0.5-1kcal/mol Bond length is about 3.6Angrstom
Coulomb’s Law
E = kq1q2/Dr E = Energy k = Constant q1q2 = 2 charges D = Dielectric charges r = Distance
Properties of Water
- Polar molecule - bent, not linear so distribution of charge is asymmetric
- Highly cohesive - interact strongly with each other through H bonding
- Hydrophobic Effect - manifestation of the properties of water
Hydrophobic Effect
Similar to putting drop of oil in water, E release and slowly move together
When separate the water around fat is same as frozen water.
Come together, some H2O is fee. Entropy - from frozen to dancing = E release
Type of reaction central in many biochemical processes
Acid-base reaction
Acid-base reactions
Central in many biochemical processes
The concentration of hydrogen ions in solution is expressed as the ph
pH
Concentration of hydrogen ions in solution
pH = -log[H+]
Also indirectly expresses the concentration of hydroxide ions [OH-], in solution.
How does pH express concentration of both [H+] and [OH-]
Water molecules dissociate to form H+ and OH- ions in an equilibrium process
Increase H+, OH- goes down
