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INTRODUCTION
Biochemistry is the systematic study of the chemicals of the living systems, their organization, and the principles of their
participation in the processes of life. Its importance is due to the increasing recognition that underlying each and every
biological function is a chemical reaction. Hundreds/thousands of chemical reactions are taking place in our cells every minute
of our lives. Biochemical investigations have been directed towards the study of the chemical composition of cells and the
chemical processes in which they participate.
Several principles are central to the understanding of living organisms:
1) Cells, the basic structural units of all living things, are highly organized.
2) Living processes consist of hundreds of chemical reactions.
3) Certain fundamental reaction pathways are found in all living organisms.
4) All organisms use the same type of molecules.
5) The instructions for growth, development, and reproduction are encoded in an organism’s nucleic acids.
The life of a cell requires materials, information, and energy:
A cell in particular, and a whole organism in general, has three basic needs: materials, information, and energy.
Without the daily satisfaction of these, human life would be severely constrained.
The organic materials of life will be considered, starting with the three main classes of foodstuffs – carbohydrates,
lipids, and proteins. Humans use these molecules to build and run their bodies and to try to stay in some state of repair. Plants
rely heavily on carbohydrate for cell walls, and animals obtain considerable energy from carbohydrates made by plants. Lipids
serve many purposes. They are used, both by plants and animals, as materials to make cell membranes and as sources of
chemical energy. Proteins are particularly important in both the structures and functions of cells. Because of the catalytic role
of proteins in regulating chemical events in cells, the study of proteins will be immediately followed with an examination of
enzymes, which make up a particular family of proteins.
Every cell has an information system – enzymes, hormones, and neurotransmitters are components of the intricate
information system in the body. Without information, the materials and energy delivered to the body could produce only
rubbish. Although enzymes are major players in the cells’ information system, they do not originate the cellular script. They
only help to carry out directions that are encoded in the molecular structures of the nucleic acids, which are compounds that are
able to direct the synthesis of enzymes. Hormones & neurotransmitters, two other components of cellular information, depend
on the presence of right enzymes not only for their existence but for their functions. Thus the study of the enzyme makers, the
nucleic acids, is included in any study of the molecular basis of life.
All life processes consist of chemical reactions catalyzed by enzymes. The reactions of a living cell, which are known
collectively as metabolism, result in highly coordinated and purposeful activity. Among the most frequent reactions
encountered in biochemical processes are:
1) nucleophilic substitution 4) isomerization
2) elimination 5) oxidation – reduction
3) addition 6) hydrolysis
To supply materials for any use – parts, information, or energy – each organism has basic nutritional needs. These
include not just organic materials, including vitamins, but also mineral, water, and oxygen. Thus, together with learning about
the materials of life and how they are processed and used, the need for vitamins, minerals, water, and oxygen will also be
considered.
