SBI4U- UNIT ONE - SBI4U Unit One2 Chemical Basis of Life...

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SBI4U: Unit One2 Chemical Basis of Life Introduction: - At the most basic level, the cell is a highly organized assemblage of atoms and molecules, programmed by genetic instructions in DNA to efficiently carry out the chemical reactions that produce the tell tale signs of life. o Signs include reproduction, growth and differentiation, response to internal and external stimuli and evolution by natural selection. - Living organisms are characterized by a balance between chemical reactions that degrade molecule’s (catabolism) and those that build them up (anabolism) o Reactions called metabolism, also govern the energy economy of the cell or organism. Chemical Basis of Life: - Millions of complex chemical reactions take place within our body at any moment. - Chemical reactions are the basis of virtually every biological process. - With the exception of water, virtually all chemicals of life are carbon based. o With a few exceptions such as CO2, virtually an organic compound. IE, organic chemistry - Major classes of organic biological importance include carbohydrates, lipids, proteins and nucleic acids. o Can only be produced in cells o Cells use this compound for growth, structure, energy, communication, metabolic processing and genetic information. Carbon: - Small, relatively light element with four single valence electrons orientated toward the vertices of a regular tetrahedral o Can form up to four stable covalent bonds with other atoms - Attach to each other to form straight and branched chains and ring structures of various sizes and complexities that act as the backbones of biological molecules. o When bonded with 4 hydrogen’s it forms a Tetrahedral (CH4) o Although the bond is slightly polar (EN: 0.4) the symmetrical shape causes it to be non- polar. o Molecules containing only carbon and hydrogen’s are called hydrocarbons. Larger hydrocarbons are also non-polar due to being symmetrical. o Ex C5H12 - Other elements such as hydrogen, phosphorous, sulfur and oxygen may attach to the carbon backbone and form functional groups. 1
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+ Amide - Most of the reactions that occur in living organisms occur in living organisms involve functional groups. o The hydroxyl group –OH and the carboxyl group –COOH are polar because of the electronegative oxygen atom they contain. o Sugars and alcohols are highly soluble in polar water because they contain polar hydroxyl groups. - Carboxyl group makes a molecule acidic whereas the amino group –NH2 makes it basic. o Compounds containing the carboxyl group are called carboxylic acids. o Amino acids (basic building block of protein) contain an amino group and a carboxyl group. Biological Macromolecules: - Many biological important molecules are called macromolecules; large molecules sometimes composed of a great number of repeating subunits. o
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This note was uploaded on 01/15/2012 for the course SCIENCE 12 taught by Professor Na during the Spring '11 term at Westmont.

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SBI4U- UNIT ONE - SBI4U Unit One2 Chemical Basis of Life...

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