MolecularCrowding - and many different enzymes Multiprotein...

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Molecular Density in an E. coli Cell Bacterial cells—prokaryotes—are often described as “bags of enzymes,” but closer study reveals several levels of subcellular organization. A typical Escherichia coli cell, shown above in cross section and magnified one million times, has several well-defined compartments. The cell is surrounded by two membranes enclosing a periplasmic compartment that is used for capturing and sorting nutrients and wastes. At the center of the cell, densely packed DNA strands are folded into a compact nucleoid, forming a loosely defined compartment devoted to storage and use of genetic information. The cytoplasm occupies the remaining portions of the cell, and is filled with ribosomes
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Unformatted text preview: and many different enzymes. Multiprotein complexes are engaged in many tasks. The flagellar motor turns a long, helical flagellum to propel the cell through its environment. Chaperonins and proteasomes oversee the folding of new proteins and the disposal of obsolete ones, respectively. DNA polymerase copies the genetic information. Some of these complexes increase efficiency by linking several tasks together: The pyruvate dehydrogenase complex performs three sequential reactions, delivering molecules from step to step using a flexible arm. (Illustration by David Goodsell.)...
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