INTRODUCTION TO BIOCHEMISTRY Medical biochemistry is an essential component

of curriculum for all categories of health professionals. Contemporary Biochemistry

plays a crucial role in the Medical field, be it metabolic pathways, storage diseases,
mechanism action of varied biomolecules or inter and intra cellular
communications. A lecture note on Medical biochemistry integrates and summarizes
the essentials of the core subject. Topics are carefully selected to cover the
essential areas of the subject for graduate level of Health sciences. The chapters
are organized around the following major themes: 1. Conformation of biomolecules,
structure and their relationship to biological activity 2. synthesis and degradation of
major metabolites 3. Production and storage of energy 4. Biocatalysts and their
application 5. Intercellular communication by hormones 6. Molecular events in gene
expression and regulation Enzymes: Body proteins perform a large number of
functions. One such unique function is, they act as biological catalysts
(Enzymes) .They are responsible for highly complex reactions. They direct the
metabolic events and exhibit specificity toward substrates, regulate the entire
metabolism. Thus, they play key role in the degradation and synthesis of nutrients,
biomolecules etc. The most important diagnostic procedures involves assay of
enzymes. They assist to know damaged tissues, the extent of tissue damage, helps
to monitor the course of the disease and used as a therapeutic means of diagnosing
a vast array of diseases. Amino acids and Proteins Living systems are made up of
Proteins .They are the dehydration polymers of amino acids. Each amino acid
residue is joined by a peptide linkage to form proteins. Proteins are the molecular
instruments in which genetic information is expressed, Hormones, Antibodies,
transporters, the lens protein, the architectural framework of our tissues and a
myriad of substances having distinct biological activities are derived. The type,
nature and number of amino acids impart characteristic properties to the proteins.
There are about 300 amino acids, but only 20 are coded by DNA of higher
organisms. Acid base properties of amino acids are important to the individual
physical and chemical nature of vii the protein. The structural organization of
proteins could be primary, secondary, tertiary and quaternary. The three
dimensional structure is the most biologically active one. The unfolding and
disorganization of the proteins results in denaturation, the process is mostly
irreversible. Such a protein may lose its biological function. Many amino acid
derived peptides are of biological importance and special products formed from
them are of critical importance to the body. Carbohydrates They are biomolecules,
found abundantly in living organisms. They contain more than one hydroxyl group
(polyhydric) In addition to aldehyde or ketone group. Thus, they form in to
polyhydroxy aldoses or polyhydroxy ketoses. Carbohydrates can be classified in to
Monosaccharide, disaccharide, and polysaccharides. Mono is the smallest sugar
unit, disaccharide is made up of two monosaccharides joined by glycosidic
linkages .The linkage can be α or β. A polymer with more than 10 monosaccharide
units is called polysaccharide. Carbohydrates have a wide range of functions. They
provide energy; act as storage molecules of energy. Serve as cell membrane
components and mediate some forms of communication between cells. Absence of
a single enzyme like lactase causes discomfort and diarrhea. The failure of
Galactose and fructose metabolism due to deficient enzymes leads to turbidity of
lens proteins (Cataract). Blood glucose is controlled by different hormones and
metabolic processes. People suffer from Diabetes if the insulin hormone is less or
not functioning well, such people are prone to atherosclerosis, vascular diseases,
and renal failure. Integrative Metabolism and Bioenergetics Oxygen is utilized for
the conversion of glucose to pyruvate. The same metabolite also forms from amino
acid and protein metabolism. Other precursors like Glycerol, propionate can give
rise to pyruvate. The main breakdown product of pyruvate is acetyl CoA, which is
the common intermediate in the energy metabolism of carbohydrates, lipid and
amino acids. It enters central metabolic pathway, the Citric acid cycle in the
mitochondrial matrix. Here it is converted to CO2, H2O and reduced coenzymes
(NADH, FADH2). These reduced nucleotides are the substrates for oxidative
Phosphorylation in mitochondria, their oxidation provide the energy for the
synthesis of ATP, the free energy currency of cells. viii Lipids The bulk of the living
matter is made up of Lipids, carbohydrates and proteins. Lipids are water insoluble,
but can be extracted with non-polar solvents like Benzene, methanol, or ether.
Some lipids act as storage molecules for example triglycerides stored in adipose
tissue. Transport forms of lipids (Lipoproteins),are present in combination with
proteins Building blocks of lipids are fatty acids. Some lipids like cholesterol lack
fatty acids but are potentially related to them. Lipids are constituents of cell
membrane and act as hydrophobic barrier that permits the entry/exit of certain
molecules. Lipids carry fat soluble vitamins and form special biomolecules. Lipid
imbalance can lead to serious diseases like obesity and atherosclerosis. Break down
of fatty acid produce energy, excessive breakdown cause ketosis, ketoacidosis,
coma and death. Cholesterol level in blood is controlled by several regulatory
mechanisms. Such information is applied in the treatment of patients with high
cholesterol levels. Vitamins and Minerals They are organic compounds required in
small quantities for the functioning of the body. They are not synthesized in the
body, needed to be provided in the diet. Vitamins do not generate energy. Generally
they are responsible for the maintenance of health and prevention of chronic
diseases. Grossly there are two groups’ Water soluble vitamins are Vit. B-complex
and C. Fat soluble vitamins are Vit A, D, E, and K. Minerals are elements present in
human body .Elements like C,H,N are provided by the diet and water .Second group
includes Ca, P, Mg, Na, K. Cl and Sulphur. These are required in large quantities
(100mg or more/day). They are called Macro elements. A third group includes trace
elements, which are required in small amounts for example Fe, I, Zn, etc. Fluorine
deficiency associated with tooth decay, excess of it causes fluorosis. Sources and
requirement are of physiological importance. The metabolic role and deficiency
disorders are important for the students of health sciences. Vitamins and trace
elements are particularly important for patients with gastrointestinal disorders, who
are fed on artificial diets or parenteral nutrition.