1.1  Introduction to Cells

big ninja

Essential Idea:

The evolution of multicellular organisms allowed 

cell specialisation and cell replacement


  • According to the cell theory, living organisms are composed of cells
  • Organisms consisting of only one cell carry out all the functions of life in that cell
  • Surface area to volume ratio is important in the limitation of cell size
  • Multicellular organisms have properties that emerge from the interaction of their cellular components
  • Specialised tissues can develop by cell differentiation in multicellular organisms
  • Differentiation involves the expression of some genes and not others in a cell’s genome
  • The capacity of stem cells to divide and differentiate along different pathways is necessary in embryonic development and also makes stem cells suitable for therapeutic uses


  • Questioning the cell theory using atypical examples, including striated muscle, giant algae and aseptate fungal hyphae
  • Investigation of functions of life in Paramecium and one named photosynthetic unicellular organism
  • Use of stem cells to treat Stargardt’s disease and one other named condition
  • Ethics of the therapeutic use of stem cells from specially created embryos, from the umbilical cord blood of a new-born baby and from an adult’s own tissues


  • Use of a light microscope to investigate the structure of cells and tissues, with drawing of cells
  • Calculation of the magnification of drawings and the actual size of structures and ultrastructures shown in drawings or micrographs