16.1 Cell Cycle

• Prokaryotic cells


  Bacteria and Blue-green algae
• Eukaryotic cells


  Protozoa, Fungi, Algae, Plants and Animals
• Prokaryotic cells


  • Genetic material or DNA is contained in one continuous strand found in the cytoplasm
  • Contain no cellular organelles (except ribosomes that manufacture proteins for the cell)
• Eukaryotic cells


  • Genetic material or DNA is contained in many short linear structures called chromosomes (called chromatin when not dividing)
  • Have membrane-bound organelles Eg. Mitochondrian, endoplasmic reticulum, golgi bodies, chloroplasts etc.
  • Have a defined nucleus which is bound by the nuclear membrane and contains the chromosomes
• Mitosis


  Chromosomes separate to ensure each daughter cell gets genetic material identical to that of the parent cell
• Cell division


  The process by which cells reproduce
• Cell cycle


  1. One cell, called the parent cell, divides to form two smaller cells called daughter cells

  2. Daughter cells then undergo a period of growth

  3. When they become the same size as the parent cell, they too begin to divide
• DNA replication in prokaryotic cells

  The long continuous strand of genetic material (circular chromosome) simply replicates itself then the cell divides by binary fission
• DNA replication in eukaryotic cells

  1. The chromosomes inside the nucleus replicate so that each chromosome has an identical copy

  2. Once the replication of genetic material is complete, the process of MITOSIS divides the genetic material EQUALLY among the daughter cells
• Interphase


  • Occurs before the actual division process takes place
  • Is a very busy time in the cell involving growth, DNA replication and protein synthesis
  • Requires approximately 19 of the 20 hour cell cycle
• Gap Phase 1 (Growth Phase 1 or G1)


  1. Occurs right after cell division and prior to S phase

  2. Growth of cellular organelles

  3. Protein synthesis

  4. Increase in the amount of cytoplasm
• Synthesis Phase or S phase


  During S-phase, the DNA replicates
• Gap Phase 2 (Growth Phase 2 or G2)

  During G2 there is a significant increase in the rate of protein synthesis as the cell prepares for division
• Mitosis


  1. Division of the chromosomes

  2. One complete set of chromosomes goes to each daughter cell guaranteeing that the genetic information in the daughter cells is identical to that in the parent cell
• Cytokinesis


  1. Division of the cytoplasm and its contents

  2. Each daughter cell gets approximately one half of the parent cell's cytoplasm and cellular organelles