Top 15 Albert L. Lehninger Quotes

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.

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.

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.

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.

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.

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.

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.

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

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

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

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

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

Cells of all kinds share certain structural features.