Post on 19-Jul-2015
AP Biology
Bonds in Biology
Strong bonds
A. Nonpolarcovalent bonds
B. Polar covalent bonds
Weak bonds
A. Ionic
B. Hydrogen bonds
C. Van der Waals forces
AP Biology
Electronegativity Review
Electronegativity = the tendency of an
atom to attract electrons
It’s better to
be negative
AP Biology
What’s up POLAR BEAR???
A molecule is polar if its components
don’t share electrons equally.
One component will pull the electrons
harder.
AP Biology
H
H
Oxygen
A. Polar covalent bonds
+
+
––
––
Pair of electrons shared
unequally by 2 atoms
Oxygen pulls the shared electrons toward itself –oxygen “wins!”
AP Biology
B. Nonpolarcovalent bond
Pair of electrons shared equally by 2
atoms
example: hydrocarbons = CxHx
methane (CH4 )Lots of
energy stored…& released
balanced, stable,
good building block
AP Biology
A. Ionic Bonds
The more electronegative atom
DOMINATES (steals the electron
completely)
Greedy polar bear
AP Biology
B. Hydrogen bonding
1) Between molecules
2) Between H+and an electronegative ion
Common electronegative ions =
O, N, F
3) WEAK
AP Biology
C. Van der Waals forces (aka
interactions) = STICKINESS
When molecules are really close, they
sometimes “STICK” because of
charges
Only lasts a short amount of time
SUPER WEAK
AP Biology
Mr. Stanley Miller and the
Primordial Soup Hypothesis
In the beginning… there was only H2O,
H2, CH4 (methane), and NH3 (ammonia).
Why is the primordial
soup hypothesis also
known as the “abiotic
synthesis of life?”
AP Biology
Organic Molecules
Made up of Carbon and Hydrogen.
Why Carbon?
Carbon makes 4 stable _________ bonds
with hydrogen
HHC
H
H
AP Biology
Hydrocarbons can have functional groups
C CH H
H H
H H
C CH H
H H
H
C CH H
H H
H
C CH H
H H
H
C CH H
H H
H
OH
H
H
H
H
=O
AP Biology
Viva la difference!
Basic structure of male & female
hormones is identical
identical carbon skeleton
attachment of different functional groups
interact with different targets in the body
different effects