lecture_10 - Major Domains of Life Based on rRNA data...

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Major Domains of Life Based on rRNA data, proposed by C. Woese Eric Gaba, NASA Lattimer, AST 248, Lecture 10 – p.1/13
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Types of Cells Prokaryotes Cells without nuclei Eukaryotes Cells with nuclei Viruses Major Differences: Prokaryotes form domains of bacteria or eubacteria and archaea. Prokaryotes form single-celled organisms, but can cluster into colonies. Prokaryotes are enclosed by a cell wall made of cross-linked chains of peptidoglycan (amino acids + sugar) which maintains size and shape of cell. Metabolism in prokaryotes is complex and more diverse. Prokaryotic genome is smaller, and its DNA is not attached to histone proteins. Most prokaryotic DNA is present in a single circular chromosome, and replication begins at a single point and proceeds around the circle in both directions. Prokaryotes obtain new genes by conjugation (transferral), transformation (absorbed from environment) and transduction (transferral by viruses or phages. Ribosomes of eubacteria differ in molecular detail from those of eukaryotes and archaea. Mariana Ruiz Lattimer, AST 248, Lecture 10 – p.2/13
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Metabolism Chemical processses that provide energy and nutrients to cells. Without cell’s presence, these reactions would occur too slowly to be useful. Cell’s primary purpose is to speed up these reactions. Metabolism requires both sources of raw materials and energy to break down old molecules and manufacture new ones. Cells have the ability to produce a large variety of products from a very limited set of starting materials, utilizing a diverse array of enzymes. Regardless of where energy comes from, cells utilize the same molecule (ATP, adenosine triphosphate) to store and release energy.
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