Use of stem cells to treat Stargardt’s disease and one other named condition.Įthics 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. Investigation of functions of life in Paramecium and one named photosynthetic unicellular organism. Questioning the cell theory using atypical examples, including striated muscle, giant algae and aseptate fungal hyphae. 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. Specialized tissues can develop by cell differentiation in multicellular organisms.ĭifferentiation involves the expression of some genes and not others in a cell’s genome.

Multicellular organisms have properties that emerge from the interaction of their cellular components. Surface area to volume ratio is important in the limitation of cell size. Organisms consisting of only one cell carry out all functions of life in that cell. § For example within humans there is a large variation in cell sizes - e.g.According to the cell theory, living organisms are composed of cells. Acetabularia) note that many of the algae (such as the more than 1 m long Caulerpa taxifolia) have multiple nuclei.įor more discussion on the relationship between organism size and cell size you could start with the following articles: For example, giant amoebas and algae (e.g. Note also that there is enormous variation in cell size within organisms§.įinally, there are many single celled organisms that have very large cells†. Larger organisms generally have more cells. There doesn't appear to be a strong correlation between organism size and cell size.

Khan academy cell biology