David Metzler – Biochemistry. The Chemical Reactions Of Living Cells (2nd edition)

Автор: David Metzler
Название книги: Biochemistry. The Chemical Reactions Of Living Cells (2nd edition)
Формат: PDF
Жанр: Биохимия
Страницы: 1977
Качество: Изначально компьютерное, E-book

Biochemistry: The Chemical Reactions of Living Cells is a well-integrated, up-to-date reference for basic chemistry and underlying biological phenomena. Biochemistry is a comprehensive account of the chemical basis of life, describing the amazingly complex structures of the compounds that make up cells, the forces that hold them together, and the chemical reactions that allow for recognition, signaling, and movement. This book contains information on the human body, its genome, and the action of muscles, eyes, and the brain.

* Thousands of literature references provide introduction to current research as well as historical background
* Contains twice the number of chapters of the first edition
* Each chapter contains boxes of information on topics of general interest

This book is about the chemistry of living cells
with special emphasis on the trillions of cells that make
up your own body. Every aspect of life depends upon
the chemical makeup of cells and on the chemical
properties of the remarkable molecules found within
the cells. The information presented here will give
the reader a solid foundation for understanding not
only the chemical basis of life but also the revolutionary
developments in molecular biology, biochemical
genetics, medicine, and agriculture which dominate
today’s scientific news and which will play an increasingly
important role in our lives.
The first theme of the book is biomolecular
structure. We’ll look carefully at the complex structures
of proteins, carbohydrates, RNA, DNA, and
many other substances. We’ll not only examine indepth
their molecular architecture but also study the
chemical properties that make life possible.
A second theme is metabolism, the unceasing,
complex network of thousands of chemical reactions
by which cells grow and reproduce, take up foods and
excrete wastes, move, and communicate with each
other. Within cells we have a steady state, a condition
in which the complex chemical constituents of
cells are continuously being synthesized in one series
of reactions and degraded in another. The result is a
marvelous system of self-renewal or “turnover” of
tissues. We’ll examine the chemical reactions involved
in these processes as well as the ways in which they
are controlled. We will consider both the reaction
sequences and the techniques such as cloning of genes,
isotopic labeling, X-ray diffraction, and nuclear magnetic
resonance spectroscopy, which are used today to
study metabolism.
Human beings are surrounded by many other living
creatures whose activities are important to us. Photosynthetic
organisms obtain energy from sunlight and
synthesize compounds that the human body requires
but cannot make. Microorganisms cause decay of
organic matter and convert it into forms usable by
plants. This book deals with the chemical reactions
occurring in all of these organisms. We’ll look at
strange and unusual reactions, along with those metabolic
sequences common to most living things.
Each one of the thousands of chemical reactions
of metabolism is catalyzed by an enzyme. Most of
these enzymes are proteins, but others are made from
RNA (ribonucleic acid). In both cases enzymes are
very large molecules with precise three-dimensional
structures. The study of the properties of enzymes
and of enzymatic catalysis is a third theme of the
book. Not only are the chemical mechanisms by
which enzymes act of interest but also enzymes are
often targets for useful drugs. Incorrectly formed enzymes
can result in serious diseases.
The sequences of the amino acids in the chains
from which proteins are constructed are encoded in
the nucleotide sequences of DNA (deoxyribonucleic
acid). The coding sequence for a protein in the DNA
is found in the structural gene for that protein. The
RNA enzymes are also encoded by DNA genes. A
fourth major theme of the book deals with the nature
of the genetic code used in DNA and with the processes
by which cells read and interpret the code. It
also includes study of the methods by which thousands
of genes have been mapped to specific positions in
chromosomes, isolated, cloned, and sequenced.
A large number of proteins present in the outer
surfaces of cells serve as receptors that receive chemical
messages and other signals from outside the cell.
The receptors, which are sometimes enzymes, respond
by generating internal signals that control metabolism
and cell growth. Such molecular signaling is another
major area of contemporary biochemistry. Biologists have described over a million species,
and several millions of others probably exist.1 Many
of these organisms have very specialized ways of life.
However, they all have much chemistry in common.
The same 20 amino acids can be isolated from proteins
of plants, animals, and microorganisms. Formation of
lactic acid in both bacteria and human muscle requires
the same enzymes. Except for some small variations,
the genetic code is universal—the same for all organisms.
Thus, there is a unity of life and we can study
metabolism as the entirety of chemical transformations
going on in all living things. However, the differences
among species are also impressive. Each species has
its own gene for almost every protein.
When the enzyme that catalyzes a particular metabolic
reaction is isolated from a number of different
organisms, it is usually found to have similar properties
and a similar mechanism of catalysis, regardless of
the source. However, the exact sequence of amino acids
in the enzyme will be almost unique to the organism
that produced it. When the three-dimensional structures
are compared it is found that differences between
species often affect only the peripheral parts of an
enzyme molecule. The interior structure of the protein,
including the catalytic machinery, is highly conserved.
However, the surface regions, which often interact with
other macromolecules, vary greatly. Such interactions
help to control metabolism and may account for many
differences in the metabolism among living beings.
Variations in protein structures are not limited to
differences between species. Individuals differ from
one another. Serious genetic diseases sometimes result
from the replacement of a single amino acid unit in a
protein by a different amino acid. Genetic deviations
from the “normal” structure of a protein result from
mutations. Many mutations, whether they occurred
initially in our own cells or in those of our ancestors,
are detrimental.
However, such mutations also account for variation
among individuals of a species and allow for evolution.
The chemical nature and consequences of mutations
and their significance to health, medicine, and agriculture
are dealt with throughout the book. We now have
reliable methods for inducing in the laboratory mutations
at any specific place in a protein sequence and
also for synthesizing new DNA sequences. These
techniques of genetic engineering have given biochemists
the ability to modify protein structures freely,
to create entirely new proteins, and to provide a basis
for the rapidly developing field of genetic therapy.
It should be clear from this introduction that
biochemistry deals with virtually every aspect of life.
The distinguishing feature of the science is that it
approaches biological questions in terms of the underlying
chemistry. The term molecular biology is often
regarded as synonymous with biochemistry.
However, some scientists use it to imply a more
biological approach. These molecular biologists also
emphasize structure and function but may have a goal
of understanding biological relationships more than
chemical details. Biophysics, a closely related science,
encompasses the application of physical and mathematical
tools to the study of life.