Mitosis

• Multicellular eukaryotic organisms require a continuous supply of new cells for growth, development and repair
• The process through which these cells are generated is known as the cell cycle
• Cell cycle


  1. Growth

  2. DNA replication

  3. Mitosis and division (cytokinesis)
• DNA


  Usually spread out in long strings when cell is not dividing, condenses into chromosomes when cell starts to prepare for division
• Chromosomes


  • Packets of DNA, each containing a large number of genes that control the development of different characteristics
  • Eukaryotic cells have two copies of each chromosome, one from mother and one from father
• Humans have 23 pairs of chromosomes, 46 chromosomes in total
• Chromosome duplication


  1. Duplicate stays attached to the original chromosome, forming an X shape

  2. Right arm of each chromosome is a duplicate of the left arm
• Cell division


  1. Chromosomes line up along the center of the cell

  2. Fibers from either side of the cell attach to respective half of each chromosome and pull the arms to opposite sides

  3. Cell membrane and cytoplasm pull apart, forming two daughter cells with identical DNA
• Resulting daughter cells can then contribute to growth, development or repair and undergo the cell cycle all over again
• Cells


  The basic building blocks of life that can replicate independently
• Multicellular organisms like animals and plants contain many cells that divide to grow or replace dead cells, not to create new organisms</b>
• Bacteria are single-celled prokaryotic organisms
• Subcellular structures common to animal and plant cells


  • Cell membrane
  • Nucleus
  • Cytoplasm
  • Mitochondria
  • Ribosomes
• Plant cells


  • Have a rigid cell wall made of cellulose
  • Contain a permanent vacuole with cell sap
  • Contain chloroplasts for photosynthesis
• Bacterial cells


  • Lack mitochondria and chloroplasts
  • Have a single circular strand of DNA instead of a nucleus
  • May have additional plasmids
  • May have flagella for movement
• Photosynthesis occurs in the chloroplasts of plant cells, using chlorophyll to absorb light energy
• Mitochondria in cells break down glucose through aerobic respiration to provide energy