BIOCHEMISTRY MEDICINE INTRODUCTION Biochemistry can be defined as

BIOCHEMISTRY & MEDICINE:

INTRODUCTION • Biochemistry can be defined as the science of the chemical basis of life (Gk bios "life"). • The cell is the structural unit of living systems. • Thus, biochemistry can also be described as the science of the chemical constituents of living cells and of the reactions and processes they undergo. • By this definition, biochemistry encompasses large areas of cell biology, molecular biology, and molecular genetics. • The Aim of Biochemistry Is to Describe & Explain, in Molecular Terms, All Chemical Processes of Living Cells • The major objective of biochemistry is the complete understanding, at the molecular level, of all of the chemical processes associated with living cells. To achieve this objective, biochemists have sought to isolate the numerous molecules found in cells, determine their structures, and analyze how they function.

The Principal Methods and Preparations Used in Biochemical Laboratories • Methods for Separating and Purifying Biomolecules 1 • Salt fractionation (eg, precipitation of proteins with ammonium sulfate) • Chromatography: Paper, ion exchange, affinity, thin-layer, gas–liquid, highpressure liquid, gel filtration • Electrophoresis: Paper, high-voltage, agarose, cellulose acetate, starch gel, polyacrylamide gel, SDSpolyacrylamide gel • Ultracentrifugation

Methods for Determining Biomolecular Structures • Elemental analysis • UV, visible, infrared, and NMR spectroscopy • Use of acid or alkaline hydrolysis to degrade the biomolecule under study into its basic constituents • Use of a battery of enzymes of known specificity to degrade the biomolecule under study (eg, proteases, nucleases, glycosidases) • Mass spectrometry Specific sequencing methods (eg, for proteins and nucleic acids)

A Knowledge of Biochemistry Is Essential to All Life Sciences • genetics The biochemistry of the nucleic acids lies at the heart of genetics; in turn, the use of genetic approaches has been critical for elucidating many areas of biochemistry. • Physiology, the study of body function, overlaps with biochemistry almost completely. • Immunology employs numerous biochemical techniques, and many immunologic approaches have found wide use by biochemists. • Pharmacology and pharmacy rest on a sound knowledge of biochemistry and physiology; in particular, most drugs are metabolized by enzyme-catalyzed reactions. Poisons act on biochemical reactions or processes; this is the subject matter of • toxicology. • pathology Biochemical approaches are being used increasingly to study basic aspects of pathology (the study of disease), such as inflammation, cell injury, and cancer.

A Reciprocal Relationship Between Biochemistry & Medicine Has Stimulated Mutual Advances • In fact, the interrelationship of biochemistry and medicine is a wide, two-way street. Biochemical studies have illuminated many aspects of health and disease, and conversely, the study of various aspects of health and disease has opened up new areas of biochemistry. Some examples of this two-way street are shown : • knowledge of protein structure and function was necessary to elucidate the single biochemical difference between normal hemoglobin and sickle cell hemoglobin. On the other hand, analysis of sickle cell hemoglobin has contributed significantly to our understanding of the structure and function of both normal hemoglobin and other proteins. • familial hypercholesterolemia, which results in severe atherosclerosis at an early age, have led to dramatic progress in understanding of cell receptors and of mechanisms of uptake of cholesterol into cells. • Studies of oncogenes in cancer cells have directed attention to the molecular mechanisms involved in the control of normal cell growth. These and many other examples emphasize how the study of disease can open up areas of cell function for basic biochemical research.

Biochemical Research Has Impact on Nutrition & Preventive Medicine • One major prerequisite for the maintenance of health is that there be optimal dietary intake of a number of chemicals; • the chief of these are vitamins, certain amino acids, certain fatty acids, various minerals, and water. Because much of the subject matter of both biochemistry and nutrition is concerned with the study of various aspects of these chemicals, there is a close relationship between these two sciences.

Most & Perhaps All Diseases Have a Biochemical Basis • We believe that most if not all diseases are manifestations of abnormalities of molecules, chemical reactions, or biochemical processes.

Macromolecules in the body : • Carbohydrates are the most abundant class of organic compounds found in living organisms. The formulas of many carbohydrates can be written as carbon hydrates, Cn(H 2 O)n, hence their name. The carbohydrates are a major source of metabolic energy, both for plants and for animals that depend on plants for food. Carbohydrates also serve as a structural material (cellulose), a component of the energy transport compound ATP, recognition sites on cell surfaces, and one of three essential components of DNA and RNA.

Macromolecules in the body : Proteins • are large biological molecules consisting of one or more chains of amino acids. Proteins perform a vast array of functions within living organisms, including catalyzing metabolic reactions, replicating DNA, responding to stimuli, and transporting molecules from one location to another. • Proteins also have structural or mechanical functions, such as actin and myosin in muscle and the proteins in the cytoskeleton. • Other proteins are important in cell signaling, immune responses, cell adhesion, and the cell cycle. • Proteins are also necessary in animals' diets, since animals cannot synthesize all the amino acids they need and must obtain essential amino acids from food. Through the process of digestion, animals break down ingested protein into free amino acids that are then used in metabolism.

Macromolecules in the body : • Lipids : are a heterogeneous group of compounds, including fats, oils, steroids, waxes, and related compounds, that are related more by their physical than by their chemical properties. • They have the common property of being (1) relatively insoluble in water and (2) soluble in nonpolar solvents such as ether and chloroform. • They are important dietary constituents not only because of their high energy value, but also because of the fat-soluble vitamins and the essential fatty acids contained in the fat of natural foods. • Fat is stored in adipose tissue, where it also serves as a thermal insulator in the subcutaneous tissues and around certain organs. • Combinations of lipid and protein (lipoproteins) serve as the means of transporting lipids in the blood.

Macromolecules in the body : • Nucleic acids, such as DNA (deoxyribonucleic acid) and RNA (ribonucleic acid), are huge polymers of nucleotides. • Every nucleotide is a molecular complex of three types of subunit molecules— phosphate (phosphoric acid), a pentose sugar, and a nitrogen-containing base: • DNA makes up the genes and stores information regarding its own replication and the order in which amino acids are to be joined to form a protein. • RNA is an intermediary in the process of protein synthesis, conveying information from DNA regarding the amino acid sequence in a protein. • The nucleotides in DNA contain the sugar deoxyribose, and in RNA they contain the sugar ribose; this difference accounts for their respective names. • there are four different types of bases in DNA: A _ adenine, T _ thymine, G _ guanine, and C _ cytosine. • The base can have two rings (adenine or guanine) or one ring (thymine or cytosine). • These structures are called bases because their presence raises the p. H of a solution. • In RNA, the base uracil replaces the base thymine.