1.1 Introduction to cells

Essential Idea:

The evolution of multicellular organisms allowed cell specialisation and cell replacement

Understandings:

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

Applications:

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

Skills:

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

Nature of science:

Looking for trends and discrepancies—although most organisms conform to cell theory, there are exceptions. (3.1) [Addressed by 1.1.A1]

Ethical implications of research—research involving stem cells is growing in importance and raises ethical issues. (4.5) [Addressed by 1.1.A4]

Theory of knowledge:

There is a difference between the living and the non-living environment. How are we able to know the difference?

International-mindedness:

Stem cell research has depended on the work of teams of scientists in many countries who share results thereby speeding up the rate of progress. However, national governments are influenced by local, cultural and religious traditions that impact on the work of scientists and the use of stem cells in therapy.

The video to the right is a talk by Manu Prakash. Manu was born in Meerut, India, but now he is a bioengineer working at Stanford University in the USA. The research done by his team has lead them to invent a 50 cent microscope which could help to save the lives of millions throughout the developing world. If you are interested get involved by contacting Foldscope.