INTRODUCTION TO BIOCHEMISTRY

The study of the chemical compounds and the chemical processes in
living organisms is called biochemistry. It plays an important role in the
expansion of biological knowledge. It gives us the understanding that how
does the biological system work. The science of biochemistry is applied in
agriculture, medicine including the whole pharmaceutical industry and food
industry. Many of the recent developments in biology like genetic
engineering, biotechnology and molecular approach to genetic disease is
due to the science of biochemistry. Biochemistry is also one of the unifying
themes in biology. There are different biochemical processes like
photosynthesis, digestion, respiration, excretion and muscle contraction. All
these chemical processes take place in a cell. These chemical processes are
maintained with high degree of organization. Metabolism is the sum of all
chemical processes taking place in the cell. It consists of two processes
anabolism and catabolism. Those reactions in which simple substances
are combined to form complex substances are called anabolic reactions.
These reactions need energy. Those reactions in which complex molecules
are broken down into simpler ones, with the release of energy are called
catabolic reactions.

Chemical composition of cell

All organisms consist of cells. The structure and functions of cells
depend on the various biochemicals which form the cells. Water forms 70%
of a typical mammalian cell. It is present throughout the cell. Water dissolves,
suspends, and ionizes materials, helps to regulate temperature of the cell.
Electrolytes are present throughout the cell. The function of the electrolytes
is to establish osmotic gradients, pH and membrane potential. Proteins are
present in the membranes, cytoskeleton, ribosomes and enzymes of the
cells. The function of the proteins is to provide structure, strength,
contractility, catalytic activity and buffering capacity to the cells. 

Lipids are present on the membranes of Golgi complex and inclusion 

of the cell. Lipids provide a reserved energy source, shape, protect and 

insulate the cells. Carbohydrates are present in the inclusions of the cells and 

provide fuel for the metabolic activities of the cell. The nucleic acid DNA is 

present in the nucleus, chromosome and gene. It controls the cell activity. 

The nucleic acid RNA is present in the nucleoplasm and cytoplasm. It 

transmits genetic information and transports amino acids. Vitamins and 

minerals are present as trace elements in cytoplasm and nucleus. Vitamins 

work with enzymes in metabolism. Minerals are essential for a normal 

metabolism, involved in osmotic balance and add strength to buffer. The 16 

elements and a few others, which occur in particular organisms are called 

bioelements, in the living body only six bioelements are present for 90% of 

the mass.

Relationship between structure and function of molecules 

Small molecules

Carbon chains make up the skeleton or backbone of organic molecules. 

Functional groups, which cluster certain atoms that always behave in a 

certain way, can be attached to the carbon chain. Functional groups also help 

-to determine the characteristics of organic molecules. The small organic 

molecules are in living things i.e., sugar, fatty acids, amino acids and 

nucleosides all have a carbon backbone and in addition, they often have one  or more of the functional groups.  

Large organic molecules                                           . Each of the small molecules can be a unit of a large organic molecule often· called a macromolecule. A unit is called monomer and the macromolecule is called polymer (GK-polys, many meros, part). Cells contain only four classes of macromolecules e.g. polysaccharides, lipids, proteins and nucleic acids. These macromolecules still have great variety and therefore play different roles in cells.