Cells - TeacherWeb

Outline the cell theory
Living organisms are made of cells
Cells are the simplest unit of life (basic unit of
structure and function).
Except for the origin of life itself, all cells come
from pre-existing cells.
Discuss the evidence for
the cell theory
1665 Robert Hooke sees cork
Same time- Anton Van Leeuwenhoek finds
1838- Botanist Schleiden: all plants are made of
1839- Biologist Schwann : all animals are made
of cells
1855- Physician Virchow: new cells come from
existing cells.
Unicellular organisms carry out all the functions
of life. These include:
Metabolism- The sum total of the chemical reactions in the body.
Response-Perceiving and responding to changes in the environment.
Homeostasis- Keeping conditions within needed limits
Growth-Increase in size
Reproduction-Producing offspring
Nutrition- Food getting to provide for life processes and growth
Compare the relative sizes of molecules, cell
membrane thickness, viruses, bacteria, organelles
and cells, using the appropriate SI unit.
Molecules- 1nm
Membrane thickness-10nm
SIze Scale
Viruses- 100nm
Bacteria- 1μm
Organelles-up to 10μm
Most cells-up to 100μm
Powers of 10
Calculate linear magnification of drawings
and the actual size of specimens in
images of known magnification.
Magnification could be stated eg x100
Magnification could be indicated with scale bar
Magnification=Drawing Size
Actual Size
100 cm
200 μm
10000 μm
2 μm
200 μm
100 cm
Explain the importance of the surface
area to volume ratio as a factor in
limiting cell size.
metabolic needs for materials and generation of
waste is dependent on volume.
Rate at which resources can be obtained and
waste removed is a function of surface area.
Emergent properties
Multicellular organisms show emergent
Cells Differentiate
By expressing some genes but not others.
Stem cells
Retain capacity to divide
Can still differentiate
Stem Cells
Give a therapeutic use
What ethical issues are involved?
Discuss balancing opportunity and risk.
Total Homework
1. Come up with a specific example of an emergent property
above the cellular level.
2. Give a specific example of cell differentiation.
3. Give a specific example of a stem cell and discuss its
4. Give a therapeutic use of stem cells.
5. What ethical issues are involved in stem cells?
6. Discuss balancing opportunity and risk with stem cell work.