CHAPTER 4 CARBON AND THE MOLECULAR DIVERSITY OF LIFE. Carbon atoms are versatile building blocks of molecules Variation in carbon skeletons contributes the diversity of organic molecules Functional groups contribute to the molecular diversity of life.
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CHAPTER 4 CARBON AND THE MOLECULAR DIVERSITY OF LIFE
Cells are 70-95% water + 5-30% carbon-based compounds.
Proteins, DNA, carbohydrates (sugars, fats, structural compounds) - all composed of carbon + other elements.
Organic compounds range from the simple (CO2 or CH4) to complex molecules, like proteins over 100,000 daltons.
In 1953, Stanley Miller (U. Chicago) was able to simulate chemical conditions on the primitive Earth to demonstrate the spontaneous synthesis of organic compounds.
6 electrons: 2 in the first shell and 4 in the second shell.
Ionic bonds are rare
Instead, carbon usually completes its valence shell by sharing electrons with other atoms in four covalent bonds.
This tetravalence by carbon makes large, complex molecules possible.
Carbon chains form the skeletons of most organic molecules.
The skeletons may vary in length and may be straight, branched, or arranged in closed rings.
The carbon skeletons may also include double bonds.
Hydrocarbons are organic molecules that consist of only carbon and hydrogen atoms.
Hydrocarbons are the major component of petroleum.
Fats are biological molecules that have long hydrocarbon tails attached to a non-hydrocarbon component.
Isomers are compounds that have the same molecular formula but different structures and therefore different chemical properties.
Butane and isobutane have the same molecular formula C4H10, but butane has a straight skeleton and isobutane has a branched skeleton.
The L-Dopa isomer is an effective treatment of Parkinson’s disease, but the D-Dopa isomer is inactive.
Functional groups replace > 1 H of a hydrocarbon.
Functional groups behave consistently from one organic molecule to another.
The number and arrangement of functional groups help give each molecule its unique properties.
The basic structure of testosterone (male hormone) and estradiol (female hormone) is identical.
They differ in the functional groups attached to the rings.
These then interact with different targets in the body.
6 functional groups are most important to the chemistry of life:
Hydroxyl (-OH): alcohols
Carbonyl (=CO): aldehydes & ketones
Carboxyl (-COOH): carboxylic acids
Amino (-NH2): amines
Sulfhydryl (-SH): thiols (& in proteins)
phosphate groups (-OPO32-): ADP, ATP, etc.
All are hydrophilic and increase solubility of organic compounds in water.
Living matter consists mainly of C, O, H, and N, with smaller amounts of S and P.
These elements are linked by strong covalent bonds.
Carbon with its four covalent bonds is the basic building block in molecular architecture.
The great diversity of organic molecules with their special properties emerge from the unique arrangement of the carbon skeleton and the functional groups attached to the skeleton.