Lecture 11
Energy and Life in Unique Environments on Earth
(Chapter 3 of Bennett, cont.)

What is common to all life?

1.  Liquid Water

Liquid water acts as an extremely efficient solvent which dissolves reactants, allowing the reactants to move around in their liquid state.  Liquid water is the best solvent in nature.

2.  Carbon Chemistry

Carbon is the only element which can form complex changes at low temperatures.

How is life based on carbon chemistry?

DNA=deoxyribonucleic acid

cytosine, thymine, adenine, and guanine or C, T A and G

These 4 bases form 2 sets of base pairs:



The ordering of the bases contains the genetic information.

Reproduction is achieved by the splitting of the DNA molecule.  The molecule splits down the middle of the base pairs.  Now each strand can attach itself to a new strand, combining together to form a new double-helix, identical to the original.  From one double helix comes 2 identical copies.

RNA=ribonucleic acid


i. mRNA (messenger RNA)--copies all the information from a DNA molecule

ii. tRNA (transfer RNA)--decodes the information on the mRNA using ribosomes and forms a new protein

iii. rRNA(ribosomal RNA)-- combines with proteins to form the ribosomes used by tRNA


*All of life today descended from a species that lived in hot springs

Note: this does not mean that life originated in hot springs


The norm for life on Earth may be hyperthermophilic and the origin may have been in a CO2 atmosphere.

Life can exist in many different environments.  Organisms are creative in their use of available energy.  In order to understand how and where life could develop in the cosmos, we must look for all the different kinds of energy sources available.

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