Lehninger Principles Of Biochemistry 6th

chapter

ifteen to twenty billion years ago, the universe arose

as a cataclysmic eruption of hot, energy-rich sub-

atomic particles. Within seconds, the simplest elements

(hydrogen and helium) were formed. As the universe

expanded and cooled, material condensed under the in-

fluence of gravity to form stars. Some stars became

enormous and then exploded as supernovae, releasing

the energy needed to fuse simpler atomic nuclei into the

more complex elements. Thus were produced, over bil-

lions of years, the Earth itself and the chemical elements

found on the Earth today. About four billion years ago,

life arose—simple microorganisms with the ability to ex-

tract energy from organic compounds or from sunlight,

which they used to make a vast array of more complex

biomolecules from the simple elements and compounds

on the Earth’s surface.

Biochemistry asks how the remarkable properties

of living organisms arise from the thousands of differ-

ent lifeless biomolecules. When these molecules are iso-

lated and examined individually, they conform to all the

physical and chemical laws that describe the behavior

of inanimate matter—as do all the processes occurring

in living organisms. The study of biochemistry shows

how the collections of inanimate molecules that consti-

tute living organisms interact to maintain and perpetu-

ate life animated solely by the physical and chemical

laws that govern the nonliving universe.

Yet organisms possess extraordinary attributes,

properties that distinguish them from other collections

of matter. What are these distinguishing features of liv-

ing organisms?

A high degree of chemical complexity and

microscopic organization. Thousands of differ-

ent molecules make up a cell’s intricate internal

structures (Fig. 1–1a). Each has its characteristic

sequence of subunits, its unique three-dimensional

structure, and its highly specific selection of

binding partners in the cell.

Systems for extracting, transforming, and

using energy from the environment (Fig.

1–1b), enabling organisms to build and maintain

their intricate structures and to do mechanical,

chemical, osmotic, and electrical work. Inanimate

matter tends, rather, to decay toward a more

disordered state, to come to equilibrium with its

surroundings.

THE FOUNDATIONS

OF BIOCHEMISTRY

1.1 Cellular Foundations 3

1.2 Chemical Foundations 12

1.3 Physical Foundations 21

1.4 Genetic Foundations 28

1.5 Evolutionary Foundations 31

With the cell, biology discovered its atom ...To

characterize life, it was henceforth essential to study the

cell and analyze its structure: to single out the common

denominators, necessary for the life of every cell;

alternatively, to identify differences associated with the

performance of special functions.

—François Jacob, La logique du vivant: une histoire de l’hérédité

(The Logic of Life: A History of Heredity), 1970

We must, however, acknowledge, as it seems to me, that

man with all his noble qualities . . . still bears in his

bodily frame the indelible stamp of his lowly origin.

—Charles Darwin, The Descent of Man, 1871

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A capacity for precise self-replication and

self-assembly (Fig. 1–1c). A single bacterial cell

placed in a sterile nutrient medium can give rise

to a billion identical “daughter” cells in 24 hours.

Each cell contains thousands of different molecules,

some extremely complex; yet each bacterium is

a faithful copy of the original, its construction

directed entirely from information contained

within the genetic material of the original cell.

Mechanisms for sensing and responding to

alterations in their surroundings, constantly

adjusting to these changes by adapting their

internal chemistry.

Defined functions for each of their compo-

nents and regulated interactions among them.

This is true not only of macroscopic structures,

such as leaves and stems or hearts and lungs, but

also of microscopic intracellular structures and indi-

vidual chemical compounds. The interplay among

the chemical components of a living organism is dy-

namic; changes in one component cause coordinat-

ing or compensating changes in another, with the

whole ensemble displaying a character beyond that

of its individual parts. The collection of molecules

carries out a program, the end result of which is

reproduction of the program and self-perpetuation

of that collection of molecules—in short, life.

A history of evolutionary change. Organisms

change their inherited life strategies to survive

in new circumstances. The result of eons of

evolution is an enormous diversity of life forms,

superficially very different (Fig. 1–2) but

fundamentally related through their shared ancestry.

Despite these common properties, and the funda-

mental unity of life they reveal, very few generalizations

about living organisms are absolutely correct for every

organism under every condition; there is enormous di-

versity. The range of habitats in which organisms live,

from hot springs to Arctic tundra, from animal intestines

to college dormitories, is matched by a correspondingly

wide range of specific biochemical adaptations, achieved

Chapter 1 The Foundations of Biochemistry

(a)

(c)

(b)

FIGURE 1–1 Some characteristics of living matter. (a) Microscopic

complexity and organization are apparent in this colorized thin sec-

tion of vertebrate muscle tissue, viewed with the electron microscope.

(b) A prairie falcon acquires nutrients by consuming a smaller bird.

FIGURE 1–2 Diverse living organisms share common chemical fea-

tures. Birds, beasts, plants, and soil microorganisms share with hu-

mans the same basic structural units (cells) and the same kinds of

macromolecules (DNA, RNA, proteins) made up of the same kinds of

monomeric subunits (nucleotides, amino acids). They utilize the same

pathways for synthesis of cellular components, share the same genetic

code, and derive from the same evolutionary ancestors. Shown here

is a detail from “The Garden of Eden,” by Jan van Kessel the Younger

(1626–1679).

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within a common chemical framework. For the sake of

clarity, in this book we sometimes risk certain general-

izations, which, though not perfect, remain useful; we

also frequently point out the exceptions that illuminate

scientific generalizations.

Biochemistry describes in molecular terms the struc-

tures, mechanisms, and chemical processes shared by

all organisms and provides organizing principles that

underlie life in all its diverse forms, principles we refer

to collectively as the molecular logic of life. Although

biochemistry provides important insights and practical

applications in medicine, agriculture, nutrition, and

industry, its ultimate concern is with the wonder of life

itself.

In this introductory chapter, then, we describe

(briefly!) the cellular, chemical, physical (thermody-

namic), and genetic backgrounds to biochemistry and

the overarching principle of evolution—the develop-

ment over generations of the properties of living cells.

As you read through the book, you may find it helpful

to refer back to this chapter at intervals to refresh your

memory of this background material.

1.1 Cellular Foundations

The unity and diversity of organisms become apparent

even at the cellular level. The smallest organisms consist

of single cells and are microscopic. Larger, multicellular

organisms contain many different types of cells, which

vary in size, shape, and specialized function. Despite

these obvious differences, all cells of the simplest and

most complex organisms share certain fundamental

properties, which can be seen at the biochemical level.

Cells Are the Structural and Functional Units of All

Living Organisms

Cells of all kinds share certain structural features (Fig.

1–3). The plasma membrane defines the periphery of

the cell, separating its contents from the surroundings.

It is composed of lipid and protein molecules that form

a thin, tough, pliable, hydrophobic barrier around the

cell. The membrane is a barrier to the free passage of

inorganic ions and most other charged or polar com-

pounds. Transport proteins in the plasma membrane al-

low the passage of certain ions and molecules; receptor

proteins transmit signals into the cell; and membrane

enzymes participate in some reaction pathways. Be-

cause the individual lipids and proteins of the plasma

membrane are not covalently linked, the entire struc-

ture is remarkably flexible, allowing changes in the

shape and size of the cell. As a cell grows, newly made

lipid and protein molecules are inserted into its plasma

membrane; cell division produces two cells, each with its

own membrane. This growth and cell division (fission)

occurs without loss of membrane integrity.

The internal volume bounded by the plasma mem-

brane, the cytoplasm (Fig. 1–3), is composed of an

aqueous solution, the cytosol, and a variety of sus-

pended particles with specific functions. The cytosol is

a highly concentrated solution containing enzymes and

the RNA molecules that encode them; the components

(amino acids and nucleotides) from which these macro-

molecules are assembled; hundreds of small organic

molecules called metabolites, intermediates in biosyn-

thetic and degradative pathways; coenzymes, com-

pounds essential to many enzyme-catalyzed reactions;

inorganic ions; and ribosomes, small particles (com-

posed of protein and RNA molecules) that are the sites

of protein synthesis.

All cells have, for at least some part of their life, ei-

ther a nucleus or a nucleoid, in which the genome—

1.1 Cellular Foundations

Nucleus (eukaryotes)

or nucleoid (bacteria)

Contains genetic material–DNA and

associated proteins. Nucleus is

membrane-bounded.

Plasma membrane

Tough, flexible lipid bilayer.

Selectively permeable to

polar substances. Includes

membrane proteins that

function in transport,

in signal reception,

and as enzymes.

Cytoplasm

Aqueous cell contents and

suspended particles

and organelles.

Supernatant: cytosol

Concentrated solution

of enzymes, RNA,

monomeric subunits,

metabolites,

inorganic ions.

Pellet: particles and organelles

Ribosomes, storage granules,

mitochondria, chloroplasts, lysosomes,

endoplasmic reticulum.

centrifuge at 150,000 g

FIGURE 1–3 The universal features of living cells. All cells have a

nucleus or nucleoid, a plasma membrane, and cytoplasm. The cytosol

is defined as that portion of the cytoplasm that remains in the super-

natant after centrifugation of a cell extract at 150,000 g for 1 hour.

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FAQs of Lehninger Principles Of Biochemistry 6th

What are the main topics covered in the 6th edition of Lehninger Principles of Biochemistry?

The 6th edition of Lehninger Principles of Biochemistry covers a wide range of topics including the structure and function of biomolecules, metabolic pathways, and the biochemical basis of genetic information flow. It delves into cellular metabolism, discussing glycolysis, the citric acid cycle, and oxidative phosphorylation. Additionally, the text examines the roles of enzymes, the principles of thermodynamics in biological systems, and the molecular mechanisms of signal transduction. Each chapter is designed to build a comprehensive understanding of how biochemical processes sustain life.

How does the 6th edition of Lehninger Principles of Biochemistry address the relationship between structure and function in biomolecules?

This edition emphasizes the critical relationship between the structure and function of biomolecules throughout its chapters. It explains how the three-dimensional structure of proteins, nucleic acids, and other biomolecules determines their specific functions in biological systems. The text includes detailed discussions on enzyme kinetics, protein folding, and the molecular basis of enzyme-substrate interactions. By integrating structural biology with functional biochemistry, the book provides a holistic view of how molecular architecture influences biological activity.

What educational resources are included in Lehninger Principles of Biochemistry 6th Edition?

Lehninger Principles of Biochemistry 6th Edition includes a variety of educational resources designed to enhance student learning. Each chapter features review questions, problem sets, and case studies that encourage critical thinking and application of biochemical concepts. Additionally, the text is supplemented with illustrations, diagrams, and tables that visually represent complex processes. Online resources may also be available, providing further interactive learning opportunities for students.

Who are the authors of Lehninger Principles of Biochemistry 6th Edition and what are their qualifications?

Lehninger Principles of Biochemistry 6th Edition is authored by David L. Nelson and Michael M. Cox, both of whom are distinguished biochemists with extensive teaching and research experience. David L. Nelson is known for his contributions to the field of biochemistry and has authored several textbooks that are widely used in academic settings. Michael M. Cox has a strong background in biochemistry and molecular biology, with a focus on the mechanisms of enzyme action and metabolic regulation. Their combined expertise ensures that the content is both accurate and pedagogically sound.

Lehninger Principles Of Biochemistry 6th

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