Albert L. Lehninger

"Biochemistry asks how the remarkable properties of living organisms arise from the thousands of different biomolecules."

"Organisms possess extraordinary attributes, properties that distinguish them from other collections of matter. What are these distinguishing features of living organisms?"

"Despite these common properties, and the fundamental unity of life they reveal, it is difficult to make generalizations about living organisms."

"The unity and diversity of organisms become apparent even at the cellular level."

"Cells of all kinds share certain structural features."

"The upper limit of cell size is probably set by the rate of diffusion of solute molecules in aqueous systems."

"All living organisms fall into one of three large groups (domains) [Bacteria, Archeara, Eukarya] that define three branches of evolution from a common progenitor."

"The distinguishing characteristics of eukary­otes are the nucleus and a variety of membrane-enclosed organelles with specific functions."

"The current understanding that all organisms share a common evolutionary origin is based in part on this observed universality of chemical intermediates and transformations, often termed "biochemical unity.""

"The chemistry of living organisms is organized around carbon, which accounts for more than half the dry weight of cells."

"We can consider cellular energy conversions—like all other energy conversions—in the context of the laws of thermodynamics."

"Virtually every chemical reaction in a cell occurs at a significant rate only because of the presence of enzymes."

"Perhaps the most remarkable property of living cells and organisms is their ability to reproduce themselves for countless generations with nearly perfect fidelity. This continuity of inherited traits implies constancy, over millions of years, in the structure of the molecules that contain the genetic information."

"Among the seminal discoveries in biology in the twentieth century were the chemical nature and the three-dimensional structure of the genetic material, deoxyribonucleic acid, DNA."

"The remarkable similarity of metabolic pathways and gene sequences across the phyla argues strongly that all modern organisms are derived from a common evolutionary progenitor by a series of small changes (mutations), each of which conferred a selective advantage to some organism in some ecological niche."

"The first living organisms on Earth doubtless arose in an aqueous environment, and the course of evolution has been shaped by the proper­ ties of the aqueous medium in which life began."

"As a result, there is an electrostatic attraction between the oxygen atom of one water molecule and the hydrogen of another (Fig. 2-lb), called a hydrogen bond."

"Water is a polar solvent. It readily dissolves most bio­ molecules, which are generally charged or polar com­ pounds (Table 2-2); compounds that dissolve easily in water are hydrophilic (Greek, "water-loving"). In contrast, nonpolar solvents such as chloroform and benzene are poor solvents for polar biomolecules but easily dis­ solve those that are hydrophobic-nonpolar molecules such as lipids and waxes."

"In thermodynamic terms, formation of the solution occurs with a fa vorable free-energy change: ΔG = ΔH - TΔS, where ΔH has a small positive value and TΔS a large positive value; thus ΔG is negative."