AP Biology 2009-2010

The

Chemistry of Life

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Outline

Review of bonds

Mr. Stanley Miller

Organic Molecules

Biomolecules

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Bonds in Biology

Strong bonds

A. Nonpolarcovalent bonds

B. Polar covalent bonds

Weak bonds

A. Ionic

B. Hydrogen bonds

C. Van der Waals forces

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Why do we care?? Bonds matter!

Eugenol Isoeugenol

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Electronegativity Review

Electronegativity = the tendency of an

atom to attract electrons

It’s better to

be negative

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What’s up POLAR BEAR???

A molecule is polar if its components

don’t share electrons equally.

One component will pull the electrons

harder.

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Strong BONDS

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H

H

Oxygen

A. Polar covalent bonds

+

+

––

––

Pair of electrons shared

unequally by 2 atoms

Oxygen pulls the shared electrons toward itself –oxygen “wins!”

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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

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ARE YOU WITH ME?

Polar covalent or Nonpolar covalent?

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ARE YOU WITH ME?

Polar covalent or Nonpolar covalent?

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ARE YOU WITH ME?

I AM SO FUNNY.

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WEAK BONDS

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A. Ionic Bonds

The more electronegative atom

DOMINATES (steals the electron

completely)

Greedy polar bear

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B. Hydrogen bonding

1) Between molecules

2) Between H+and an electronegative ion

Common electronegative ions =

O, N, F

3) WEAK

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Examples of Hydrogen Bonds

Hydrogen Bonds are common in

Biology!

H

O

H

H bonds

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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

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Why are we studying chemistry?

Chemistry is the origin of life.

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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?”

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Organic Molecules

Made up of Carbon and Hydrogen.

Why Carbon?

Carbon makes 4 stable _________ bonds

with hydrogen

HHC

H

H

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Hydrocarbons

Special name given to

chains of C &H

Polar or Nonpolar?

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Hydrocarbons can grow and change

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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

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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

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BIOMOLECULES

Hydrocarbon chain with functional

groups

4 major types STAY TUNED!!

Carbohydrates

Lipids

Proteins

Nucleic acids Is water a

biomolecule?????