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BIO203 - Chapter 2 Summary

BIO203 - Chapter 2 Summary - CHAPTER TWO SUMMARY...

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CHAPTER TWO SUMMARY INTRODUCTION The complex organization and interaction of the chemicals within a cell confer the unique characteristics of life. The key chemicals of life are water, certain small inorganic solutes such as salts, and four categories of organic molecules: lipids, carbohydrates, amino acids and proteins, and nucleotides and nucleic acids. •Large organic complexes and macromolecules—membranes, polysaccharides, proteins, and nucleic acids—are responsible for the main structures and functions of cells. Functions often require that these complexes and macromolecules be flexible and dynamic, but in turn, they are susceptible to disruption by some environmental factors such as temperature. Thus, homeostasis of the interior environment in organisms in part evolved to protect the macromolecules, especially proteins. Cells are the living building blocks of multicellular bodies. Body cells, which are too small to be seen by the unaided eye, have been shown by microscopic techniques to consist of three major subdivisions: (1) the plasma membrane, which encloses the cell and separates the intracellular and extracellular fluid; (2) the nucleus, which contains deoxyribonucleic acid (DNA), the cell’s genetic material; and (3) the cytoplasm, the portion of the cell’s interior not occupied by the nucleus. •The cytoplasm consists of cytosol, a complex gelatin-like mass, and organelles, which are highly organized, membrane-enclosed structures dispersed within the cytosol. NUCLEUS, CHROMOSOMES AND GENES •The eukaryotic nucleus contains deoxyribonucleic acid, DNA, in linear strings called chromosomes. DNA consists of a varying 4 nucleotides designated A, G, T, and C. The sequence of a particular stretch of DNA, called a gene, contains a code for making proteins, and a regulatory sequence for controlling the coding region of the gene.
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•A gene is transcribed (copied) as an mRNA (messenger RNA) (ribonucleic acid, made of 4 nucleotides designate A, G, U, and C). mRNA then binds to a ribosome, where it is translated (by synthesis of a molecule made of amino acids) into a protein. •Different genes are expressed in different tissues and organs. Special proteins, transcription factors, which often differ among tissues, recognize the regulatory sequence of a gene. Following recognition by these factors, transcription of the nearby coding section of the gene ensues.
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BIO203 - Chapter 2 Summary - CHAPTER TWO SUMMARY...

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