All living things are made of cells, which are the basic functional units of life. Cells come from pre-existing cells through reproduction. However, there are some exceptions, such as mitochondria, chloroplasts, and viruses, which are not made of typical cells. Stem cells are unique in their ability to self-renew through numerous divisions while maintaining their undifferentiated state, and in their potency to differentiate into specialized cell types. This makes them promising for medical therapies but also controversial due to ethical concerns.

1. Topic 1: Cells
Exceptions to Cell
Theory &
Differentiation

3. Functions of Life
All systems classified as
“living” must be able to do the
following on their own:
Reproduce + Pass on genes
Evolve + Respond + Adapt to
their changing environment
Metabolize nutrients + Excrete
Waste
Grow + Develop over time
Maintain Homeostasis

5. The Cell Theory
Once we know something is
living, we also know it must
follow the Cell Theory:
All living things are made of
cells.
Cells are the most basic unit of
life.
Existing cells come from pre-
existing cells.

6. Exceptions to Cell Theory
1. Mitochondria & chloroplasts
2. Viruses
Tissues and organisms not made of typical
cells:
1. Skeletal muscle
2. Giant algae
3. Aseptate fungi

7. Past paper question

8. What two things set stem cells
apart from “regular cells?
Self-renewal
The ability to go
through numerous
cycles of cell division
while maintaining the
undifferentiated
state
Potency
Stem cells are
undifferentiated and have
the capacity to differentiate
down different paths into
specialized cell types.
This requires stem cells to
be either totipotent or
pluripotent to be able to
give rise to any mature cell
type

10. Adult stem cells have
been used for many
years to treat leukemia
through bone marrow
transplants.
The bone marrow
contains cells that
differentiate into the
different types of blood
cells.
Why is stem cell research controversial?
On what basis do people object to it?

11. Differentiation
Cells become specialized
for different functions by the
process of differentiation
Gives an advantage to
multicellular organisms by
allowing for a division of
labor

12. Emergent properties
When units of biological material are put
together, the properties of the new material are
not always additive, (equal to the sum of the
properties of the components).
Instead, at each level, new properties and rules
emerge that cannot be predicted by observations
and full knowledge of the lower levels. Such
properties are called emergent properties
(Novikoff, 1945).
Life itself is an example of an emergent
property.
For instance, a single-celled bacterium is alive, but if
you separate the macromolecules that combined to
create the bacterium, these units are not alive. Based on
our knowledge of macromolecules, we would not have
been able to predict that they could combine to form a
living organism, nor could we have predicted ALL of the
characteristics of the resulting bacterium.