【生物课件】Chapter 6 Nutrition and Metabolism.pptVIP

Growth may be generally defined as a steady increase in all of the chemical components of an organism. Growth usually results in an increase in the size of a cell and frequently results in cell division Growth definition: * G1 Primary growth phase of the cell during which cell enlargement occurs, a gap phase separating cell growth from replication of the genome S phase in which replication of the genome occurs G2 Phase in which the cell prepares for separation of the replicated genomes, this phase includes synthesis of microtubules and condensation of DNA to form coherent chromosomes, a gap phase separating chromosome replication from miosis. M phase called miosis during which the microtubular apparatus is associated and subsequently used to pull apart the sister chromosomes. Cell life cycle in Eukaryotic cells G1 S G2 M G1 R D Eukaryotic cell: Prokaryotic cell: * * Most bacterial cells reproduce asexually by binary fision, a process in which a cell divides to produce two nearly equal-sized progeny cells. Binary fision involves three processes: Increase in cell size (cell elongation), DNA replication Cell division Binary fision * Growth curve of bacteria Lag Phase Exponential Phase ?Stationary Phase Death Phase * Growth curve of bacteria Lag Phase Exponential Phase ?Stationary Phase Death Phase * (a)????? Lag phase: cells begin to synthesize inducible enzymes and use stored food reserves. (b)???? Logarithmic growth phase: the rate of multiplication is constant. (c)????? Stationary phase: death rate is equal to rate of increase. (d) Death phase: cells begin to die at a more rapid rate than that of reproduction. Lag Phase Stationary Phase Death Phase Logarithmic growth phase * The time required for a cell to divide (and its population to double) is called the generation time. generation time Suppose that a bacterial population increases from103 cells to 109 cells in 10 hours. Calc