Cell biology

• Cell theory


  Developed to explain basic features of structure
• Cell theory generalizations


  • All living things are composed of cells
  • Cells are the smallest functional unit of life
  • New cells arise from pre-existing cells
• The cell theory is a generalization that applies to most but not all organisms
• Exceptions to cell theory


  • Giant Algae: one multi-nucleated cell that grows to a large size without separate cells
  • Striated Muscle Fibres: large multi-nucleated fibre formed from fusion of muscle stem cells
  • Fungal Hyphae: Aseptate hyphae that do not contain cross walls
• 7 functions of life


  • Metabolism
  • Response
  • Homeostasis
  • Growth
  • Reproduction
  • Excretion
  • Nutrition
• Larger surface area to volume ratio

  Achieved when the cell gets smaller, making diffusion of nutrients and waste materials more effective
• There is a physical limit to size a cell can grow
• Multi-cellular organisms are the result of working around the physical limit to cell size
• Magnification


  Measured length / Actual length
• Emergent property


  Whole is greater than the sum of its parts
• Emergent properties of multi-cellular organisms


  • Greater properties that arise from interactions of cellular components
  • Biochemical reactions produce emergent property of metabolism
  • Muscle tissue has properties of contraction and elasticity
  • Circulatory system has emergent properties of circulation and exchange
• Stem cells


  Undifferentiated cells characterized by self-renewal and potency
• Categories of stem cells


  • Totipotent- can differentiate into all types of cells
  • Pluripotent- can differentiate into majority of cell types
  • Multipotent- can differentiate into a limited number of related cell types
• Potency of stem cells


  Depends on origin: Embryonic Stem Cells (ESCs) are pluripotent, Adult Stem Cells (ASCs) are multipotent
• Applications of stem cells


  • Produce regenerated tissue for skin grafts
  • Healing diseases where type of cell is lost (type 1 diabetes)
  • Possibility of being used to grow organs
  • Renewable source of cells for scientific studies and tests
• Specific stem cell applications


  • Stargardt's Disease: ESCs injected to replace degenerated retinal cells to restore vision
  • Leukemia: ASCs used to replace mutated and destroyed stem cells in bone marrow killed by chemotherapy