Guide to Biochemistry

James C. Blackstock

• Editore: Butterworth-Heinemann
• Anno: 2014
• ISBN:
  9781483183671
• Argomento: Biowissenschaften
• Categoria: Biologie

Guide to Biochemistry provides a comprehensive account of the essential aspects of biochemistry. This book discusses a variety of topics, including biological molecules, enzymes, amino acids, nucleic acids, and eukaryotic cellular organizations. Organized into 19 chapters, this book begins with an overview of the construction of macromolecules from building-block molecules. This text then discusses the strengths of some weak acids and bases and explains the interaction of acids and bases involving the transfer of a proton from an acid to a base. Other chapters consider the effectiveness of enzymes, which can be appreciated through the comparison of spontaneous chemical reactions and enzyme-catalyzed reactions. This book discusses as well structure and function of lipids. The final chapter deals with the importance and applications of gene cloning in the fundamental biological research, which lies in the preparation of DNA fragments containing a specific gene. This book is a valuable resource for biochemists and students.

CHAPTER 1

Biological molecules

Publisher Summary

This chapter provides an overview of biological molecules. The word cell was introduced to biology in 1665 by Robert Hooke in his collection of microscopic drawings, called Micrographia, which included one of a thin slice of cork. There are 92 natural chemical elements of which living cells contain only approximately 27. The actual number depends on the type of cell and species of the organism. The bonding of four different groups to a carbon atom results in two possible tetrahedral structures. As the molecules have identical composition but different structures, they are called isomers. Isomers that differ in the spatial arrangement of the atoms in the molecules are called stereoisomers. The chapter also presents the nature of macromolecules. The classes of biological macromolecules are not mutually exclusive and may interact to produce hybrid or conjugate molecules. The chapter also discusses the functions of macromolecules and monomeric units. Biological activity is not confined to monomeric units or large polymeric chains.

1.1 Cell theory

The word cell was introduced to biology in 1665 by Robert Hooke in his collection of microscopic drawings, called Micrographia, which included one of a thin slice of cork. He recorded the honeycomb structure of cork and referred to the compartments as cells by analogy to the cell of a prisoner or monk. The term, however, has been retained not to describe the voids remaining after the disintegration of cell cytoplasm (observed by Hooke) but the living contents normally resident between these plant cell walls. Today, the cell may be defined as the simplest integrated unit in living systems capable of independent survival.

By the early nineteenth century, recognition was given to cells as life forms and their organization into more complex multicellular organisms. In 1839, Theodor Schwann, a zoologist, published Mikroskopische Untersuchungen, which also contained figures supplied by Mathias Schleiden, a botanist, to record that plants and animals are composed of similar cells. Twenty years later, Rudolf Virchow announced ‘omnis cellula e cellula’, i.e. all cells arise from pre-existing cells.

Despite the wide variety of cell types, most cells can be classified according to their size and complexity into one of two categories: prokaryotes or eukaryotes. These terms are derived from Greek, karyon meaning kernel as in a nut, pro- meaning before and eu- meaning well. The eukaryotes therefore contain a well-formed nucleus (Latin for nut) whereas the prokaryotes are devoid of a discrete nucleus since their genetic material is not enclosed by an intracellular membrane.

A definitive feature of prokaryotic cells is their lack of membrane-bound structures although layers of internal membranes may arise from the plasma membrane. In contrast, eukaryotic cells contain numerous membrane-bound organelles, e.g. mitochondria, chloroplasts, endoplasmic reticulum, Golgi apparatus and microbodies. Although the size of cells of both categories are variable, in general, prokaryotic cells range from 0.1 to 3 μm whereas the dimensions of most eukaryotic cells are 10 to 20 μm. Prokaryotic organisms may be subdivided into three groups: bacteria, mycoplasmas and cyanobacteria which differ morphologically.

During the 1970s, the dichotomy of cells into prokaryotic and eukaryotic began to be challenged by the discovery of a few classes of bacteria, called archaebacteria, which, although possessing the general structural features of prokaryotic cells, exhibit distinctive biochemical characteristics.

1.2 The role of carbon

There are 92 natural chemical elements of which living cells contain only approximately 27. The actual number depends on the type of cell and species of the organism. Over 99% of the mass of most cells is composed of only six elements which are called the major el...