Transcript Cell Theory Timeline

UNIT 4: Cells
BIG IDEA: There are different levels
of organization in organisms, with
cells being the basis of all life.
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.
Late1600’s: Anton van Leeuwenhoek
• Builds simple, powerful
microscopes and 1st to see living
cells
• Observes blood cells, animal
sperm cells, & bacteria from
his own teeth! He called
them “animalcules”
Cell Theory
• The observations about cells from the past
150 years is becoming more organized in
the 1800’s
• Schleiden, Schwann and Virchow are the
scientists who contribute to developing a
unifying cell theory
• 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.
• 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.
Surface area-to-volume Ratio
larger the surface• As the cell gets ______,
smaller
area-to-volume ratio gets _________.
• If the cell grows beyond a certain
limit, not enough material will be
able to cross the membrane fast
enough to provide for the increased
volume.
Surface area-to-volume ratio
Length of
side
Surface
Area
Volume Surface Area/
Volume
1
6
1
6
2
24
8
3
4
96
64
3/2 = 1.5
Surface area-to-volume ratio
• Materials must enter through the
surface.
• The bigger the cell, the smaller the
surface area-to-volume ratio.
• 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?