Principles of Biochemistry Lec 4 PDF

Five Types of Chemical Transformations Occur in Cells  Most cells have the capacity to carry out thousands of specific, enzyme catalyzed reactions: transformation of simple nutrients such as glucose into amino acids, nucleotides, or lipids; extraction of energy from fuels by oxidation; or...

Five Types of Chemical Transformations Occur in Cells  Most cells have the capacity to carry out thousands of specific, enzyme catalyzed reactions: transformation of simple nutrients such as glucose into amino acids, nucleotides, or lipids; extraction of energy from fuels by oxidation; or polymerization of subunits into macromolecules, for example.  Most of the reactions in living cells fall into one of five general categories: functional-group transfers (a), oxidations and reductions (b), reactions that rearrange the bond structure around one or more carbons (c), reactions that form or break carbon-carbon bonds (d), and reactions in which two molecules condense, with the elimination of a molecule of water (e). Reactions within one category generally occur by similar mechanisms.  CHO Protein Lipid Oxidizable food Food stuffs Non- oxidizable food  Vitamins  Vitamins may be regarded as organic compounds required in small amounts to perform specific biological functions for normal maintenance of optimum health of the organism.  Thus we must obtain them from the foods we eat, or via vitamin supplements. Supplements: Synthetic or natural substances which can be purchased as pills, tablets, capsules, wafers, powders, or liquids. A balanced diet prepared from fresh food stuffs usually contains the necessary amounts of all vitamins.  A prolonged low supply of some of the vitamins may cause either hypovitaminosis  This condition may caused as a result of decreased intake ,impaired absorption, Increased metabolism or inadequate storage.  Toxicity can result from excessive intake of some vitamins (Vitamin A &D) and this condition is called hypervitaminosis. Vitamers are different forms of one vitamin.  Some good examples of vitamers : o Retinol, retinal and retinoic acid are vitamers of vitamin A. o Pyridoxine, pyridoxal and pyridoxamine are vitamers of vitamin B6. Provitamin are precursors of vitamins that converted into vitamins inside the body.  Classification of vitamins Two distinct types: Fat soluble (A, D, E, K) Water soluble (B –complex, C)  Hydrophobic  Its absorption need bile salts  Heat stable  Unstable to oxygen and sunlight