Carbon and the Molecular Diversity of Life Chapter 4: Carbon and the Molecular Diversity of Life

Overview: Carbon: The Backbone of Life Living organisms consist mostly of carbon-based compounds Carbon is unparalleled in its ability to form large, complex, and diverse molecules Proteins, DNA, carbohydrates, and other molecules that distinguish living matter are all composed of carbon compounds © 2011 Pearson Education, Inc.

Life is based on carbon

Organic Molecules and the Origin of Life on Earth Stanley Miller’s classic experiment demonstrated the abiotic synthesis of organic compounds Experiments support the idea that abiotic synthesis of organic compounds, perhaps near volcanoes, could have been a stage in the origin of life © 2011 Pearson Education, Inc.

Inquiry Could organic compounds have been synthesized abiotically on the early Earth? EXPERIMENT In 1953, Stanley Miller simulated what were thought to be environmental conditions on the lifeless, primordial Earth. As shown in this recreation, Miller used electrical discharges (simulated lightning) to trigger reactions in a primitive “atmosphere” of H2O, H2, NH3 (ammonia), and CH4 (methane)—some of the gases released by volcanoes. RESULTS A variety of organic compounds that play key roles in living cells were synthesized in Miller’s apparatus. CONCLUSION Organic compounds may have been synthesized abiotically on the early Earth, setting the stage for the origin of life. (We will explore this hypothesis in more detail in Chapter 26.)

Hydrocarbons Hydrocarbons are organic molecules consisting of only carbon and hydrogen Many organic molecules, such as fats and carbohydrates, have hydrocarbon components Hydrocarbons can undergo reactions that release a large amount of energy © 2011 Pearson Education, Inc.

The role of hydrocarbons in fats (a) A fat molecule (b) Mammalian adipose cells 100 µm Fat droplets (stained red)

Isomers Isomers are compounds with the same molecular formula but different structures and properties Structural isomers have different covalent arrangements of their atoms Cis-trans isomers have the same covalent bonds but differ in spatial arrangements Enantiomers are isomers that are mirror images of each other © 2011 Pearson Education, Inc.

(a) Structural isomers Three types of isomers H CO2H CH3 NH2 C X (a) Structural isomers (b) Geometric isomers (c) Enantiomers L isomer D isomer

The pharmacological importance of enantiomers L-Dopa (effective against Parkinson’s disease) D-Dopa (biologically inactive)

Oliver Sachs discovered a major role for L-dopa in the treatment of Parkinson-like diseases.

Effective Enantiomer Ineffective Enantiomer Pain; inflammation Figure 4.8 Effective Enantiomer Ineffective Enantiomer Drug Condition Pain; inflammation Ibuprofen S-Ibuprofen R-Ibuprofen Figure 4.8 The pharmacological importance of enantiomers. Albuterol Asthma R-Albuterol S-Albuterol

The Chemical Groups Most Important in the Processes of Life Functional groups are the components of organic molecules that are most commonly involved in chemical reactions The number and arrangement of functional groups give each molecule its unique properties © 2011 Pearson Education, Inc.

A comparison of functional groups of female (estradiol) and male (testosterone) sex hormones CH3 OH HO O Estradiol Testosterone Female lion Male lion