Introduction To Biochemistry : Amino acids and Proteins, Integrative Metabolism and Bioenergetics, Lipids and Hormones
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 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.
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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.
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.
Hormones
Hormones are chemical messengers secreted by endocrine glands and specific tissues. They reach distant organs and stimulate or inhibit the function. They play important role in carrying messages to the various organs. They form part of a signaling system.
Hormones are synthesized in one tissue, secreted in to blood, transported as mobile messengers When they reach target tissue, they exhibit their actions. Defect in the secretion, function, metabolism can lead to various diseases.
Molecular Biology
Human beings are highly developed species. How a person looks, behaves, suffers from diseases and the like are dictated by genetic material called DNA. The information is inherited from parent to offspring. The same is replicated from parent DNA to daughter DNA.
Individual characters are translated in to proteins, under the direction of DNA. First RNA is synthesized from DNA (Transcription) which is translated in to Proteins. These proteins are
responsible for various metabolic functions. Protein expression during development, adaptation,
aging and other related processes of life are controlled by DNA. Changes in the genetic material cause hereditary diseases.
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