1. Topic 2.1 - Cell Theory
2.1.1 Outline the cell theory.
• All living things are made of one or more cells.
• The cell is the basic unit of life.
• All cells come from pre-existing cells.
2.1.2 Discuss the evidence for cell theory.
• It is important to note that all "rules" have exceptions.
• Connective tissue, such as bone, blood and cartilage, is composed of both cellular and
extracellular structures, especially extracellular proteins and fluids.
• Skeletal muscle and some fungal hyphae have multinucleate cytoplasm, lacking normal cell
separations.
• Some biologists consider unicellular organisms to be acellular.
2.1.3 State that unicellular organisms carry out all the functions of life.
• Unicellular organisms carry out all the functions of life, including metabolism, response,
homeostasis, growth, reproduction and nutrition.
2.1.4 Compare the relative sizes of molecules, cell membrane thickness, viruses, bacteria,
organelles and cells, using appropriate SI units.
• 1000 nm(nanometer) = 1 um, 1000 um = 1mm
• molecules: ~ 1 nm
• cell membrane thickness: ~ 10 nm
• viruses: ~ 100 nm
• bacteria: ~ 1 µm
• organelles: up to 10 µm
• eukaryotic cells: up to 100 µm
2.1.5 Calculate linear magnification of drawings.
Drawings of microscopic structures must include
1

2. Scale bars: |-----------| = 1 µm
OR magnification: x 250
2.1.6 Explain the importance of the surface area to volume ratio as a factor limiting cell size.
• As the dimensions of a cell increase, volume increases proportionally faster than surface area
• Thus, surface area: volume ratio decreases with cell size.
• Setting an upper limit on cell size.
• Because lower relative SA reduces rate of exchange.
• While higher relative volume increases metabolic demands.
• Thus, rate of exchange can’t meet needs of metabolic demands.
2.1.7 State that multicellular organisms show emergent properties.
• Emergent properties arise from the interaction of component parts: the whole is greater than the
sum of its parts.
2.1.8 State that multicellular organisms differentiate to carry out specialized functions by
expressing some of their genes but not others.
• In multicellular organisms, all the cells contain all the genes, but they do not use all of them. The
cells of a multicellular organism differentiate to carry out specialized functions by only expressing
some of their genes.
2.1.9 State that stem cells retain the capacity to divide and have the ability to differentiate along
different pathways.
• “Stem cells are like toenail clippings with a better career plan!”
2.1.10 Outline one therapeutic use of stem cells.
 Molly Nash was born in 1994 with Fanconi anaemia, a rare genetic condition in which the body
cannot make healthy bone marrow. Sufferers rarely reach adulthood.
 Her parents produced an embryo by IVF and then tested to ensure a tissue match with Molly.
 The embryo was transferred into Mrs. Nash to create a possible donor sibling for Molly.
 Baby Adam was born in 2000.
 Blood from his umbilical cord was collected at birth and stem cells from it successfully used as a
bone marrow graft for Molly.
2