Chapter 4: Carbon and the Molecular Diversity of Life

Chapter 4: Carbon and the

Molecular Diversity of Life

Essential Knowledge 1.d.1 – There are several hypotheses

about the natural origin of life on Earth, each with supporting scientific evidence (4.1).

2.a.3 – Organisms must exchange matter with the environment to grow, reproduce, and maintain organization (4.1 & 4.2).

Organic Chemistry The study of carbon compounds. Usually involves the study of living

things

Major Elements Of Organic Molecules Carbon: +4 or -4 Hydrogen: +1 Oxygen: -2 Nitrogen: -3

Hydrocarbons Organic

molecules made of only carbon and hydrogen.

Carbon’s versatility Forms 4 covalent bonds

(because it has 4 valence e-)

Molecular shape is tetrahedral

Bonds very easily to itself

Carbon, continued Can form nearly 10 million

compounds 15 known isotopes: C-14 (age of

fossils), C-13, C-12 Naturally occurring in hardest

(diamonds) and one of softest (graphite) forms on Earth

Carbon, continued Very small size (capable of forming

multiple bonds) Major economic use—petroleum,

other fossil fuels Others: pencil “lead”, steel, charcoal,

medicine

Organic Isomers Compounds with the same molecular

formula but have different structures. Result: Different molecular and

chemical properties.

Which of these are isomers?

No Yes

Yes No

3 Types Of Isomers1. Structural2. Geometric (cis/trans)3. Enantiomers

1. Structural Isomers Different in covalent arrangements

of their atoms.

Butane Isobutane

2. Geometric Isomers Same covalent partnership but differ

in spatial arrangements. Arise from the inflexibility of double

bonds. Also known as cis/trans isomers

3. Enantiomers Molecules

that are mirror images of each other.

Usually involve an asymmetric carbon.

Comment Organisms are sensitive to even the

most subtle variations in molecular architecture.

This is why isomers (and their shape/characteristics) are critical to biochemistry

Example - Thalidomide Cells can’t distinguish between two

isomers. One is an effective drug. The other causes birth defects. Used (in 1970s) as a “cure” for mornin

g sickness

Functional Groups A group of atoms attached to a

carbon skeleton. Have consistent properties. Their number and kind give

properties to the molecule.

Importance of Functional Groups

Figure 4.9

Memorize!!!

Hydroxyl Group A hydrogen atom bonded to an

oxygen atom. Ex. -OH Very polar. Allows the material to be

hydrophilic. Forms alcohols.

Carbonyl Group A carbon atom joined to an oxygen

atom by a double bond. Ex. - C=O Polar tendencies Two types of Carbonyl Group

compounds:• Aldehydes• Ketones

Carbonyl: Aldehydes A carbonyl group at the end of a

carbon skeleton. Ex. - C=O

H

Sometimes written as - CHO

Carbonyl: Ketones A carbonyl group in the middle of a

carbon chain. Ex. -C-C-C- || O

Carboxyl Group Group with a carbon double

bonded to an oxygen and to a hydroxyl group.

Ex. - C=O| OH

Written as: -COOH Also called Carboxylic Acids

• Donate H+ (acid).• Form many weak organic acids.

Amino Group Nitrogen bonded to two hydrogens.

Ex. – N-H

| H Forms compounds called amines. Act as a base. IF combined with

carboxyl, can act as an acid!• Ex: amino acids

Sulfhydryl Group Sulfur bonded to a hydrogen. Ex. -SH Forms compounds called thiols. Help with protein structure. Acidic properties

Phosphate Group Phosphorus with four oxygens. Ex. -PO4 Has a net -2 charge. Sometimes written as “Pi”. Involved with energy transfers.

Methyl Group Carbon bonded to three hydrogens. -

CH3 Very non-polar and hydrophobic. Ex: fossil fuels (any other

hydrocarbon)

Summary Identify what is meant by organic

chemistry. Recognize the valences for the major

elements of organic molecules. Recognize various types of isomers. Identify the functional groups and

their structure and properties.