Transcript Organelles - Schoolwires

Cell Theory
Timeline
What is a cell?
• The basic unit of structure
and function of life.
1665: Robert Hooke
• Builds compound microscopes
and first to observe cork cells.
• Coined term “cell”
1683: Anton van Leeuwenhoek
• Builds simple, powerful
microscopes
• Observes many single celled
organisms, (like blood cells,
animal sperm cells, & bacteria
from his own teeth! He called
them “animalcules” )
Discoveries that Led to Cell
Theory
• Developed mainly by 3 German
Scientist’s discoveries:
a. Matthias Schleiden
b. Theodor Schwann
c. Rudolph Virchow
• 1838: Matthias Schleiden
Concludes all plants are made
of cells
• 1839: Theodor Schwann
Concludes all animals are
made of cells.
• 1855: Virchow
Concludes that all cells come
from pre-existing cells
Cell Theory
1. All organisms are composed
of one or more cells.
2. Cells are the basic units of
structure and function in an
organism.
3. Cells come only from the
reproduction of existing cells.
Cell Diversity
• Shape: There are many cell
shapes. The function of the
cell influences the shape of the
cell.
For example, skin cells are
flat, nerve cells have
extensions.
Skin Cells
Nerve cell
Size
• Different types of cells have
different sizes.
0.1 μm – 100 μm
• The size of a cell is limited by
the surface area-to volume
ratio.
• As the cell gets larger, the
surface-area-to-volume ratio
gets _smaller_.
Surface area-to-volume ratio
• Materials must enter through the
surface.
• If a cell is too large, there is not
enough surface area to allow
materials to pass through quickly
enough.
Types of Cells
Prokaryotic vs. Eukaryotic
Prokaryotic Cells
1. Very simple cell
2. Generally smaller
3. NO membrane-bound
organelles (compartments)
4. No true nucleus.
– DNA is found in the nucleoid
region and is NOT separated
by a membrane.
5. Example is bacteria.
Eukaryotic Cell
1. More complex cells
2. Generally bigger
3. Contains membrane-bound
organelles
4. Has a true nucleus
– Region of where DNA is
stored and is separated by a
membrane.
5. Examples are animals & plants
Pop Quiz!
1. Who is credited for first seeing
cells?
2. According to the Cell Theory,
where do all cells come from?
3. Which cells are simpler:
Prokaryotic or Eukaryotic?
4. Which cells contain membranebound organelles?
5. Which type of cells do you have?