CELLS
6th grade
WHAT IS A
CELL?
 A cell is the smallest
functional and structural
unit of all living organisms.
 Some organisms are just
one cell like bacteria.
Others, like humans,
contain trillions of cells.
Example: blood cells, white
blood cells, nerve cells, skin
cells, etc.
Examples
White blood cells
Skin cells
Nerve cells
What is the cell theory?
Discoveries of Matthias Schleiden, Theodor
Schwann, and Rudolf Virchow led to one very
important theory called the cell theory.
The cell theory lists three basic characteristics of all
cells and organisms:
1. All organisms are made up of one or more cells.
2. The cell is the basic unit of all organisms.
3. All cells come from existing cells.
All Organisms Are Made Up of One or
More Cells
 Anton Van Leeuwenhoek – was the first person to describe actual
living cells when he looked at a drop of pond water under a
microscope.
 In 1838, Matthias Schleiden concluded that plants are made of
cells.
 In 1839, Theodor Schwann determined that animal tissues are
made of cells. He concluded that all organisms are made up of
one or more cells.
 Unicellular organisms- organisms that are made up of one cell.
 Multicellular organisms – organisms that are made up of more
than one cell.
All Organisms Are Made Up of One or
More Cells
Schwann wrote the first two parts of the cell
theory. In 1858, Rudolf Virchow added the third
part of the cell theory that all cells come from
existing cells.
What parts do all cells have in
common?
 All cells have some parts in common, including cell membranes,
cytoplasm, organelles, and DNA.
 Cell membrane – is the protective layer that covers a cell’s
surface and acts as a barrier.
 Cytoplasm – is the fluid that all organelles are suspended.
 Organelles – is a small body in a cell’s cytoplasm that is
specialized to perform a specific function.
 DNA – is located inside the nucleus. Deoxyribonucleic acid, or
DNA, is genetic material that provides instructions for all cell
processes.
DNA
KARYOTYPE - FEMALE
KARYOTYPE - MALE
Two types of
cells
Prokaryotic: is a
single celled
organism that
does not have a
nucleus or
membranebound
organelles.
Two types of
cells
Eukaryotic: is
an organism
made up of
cells that
contain their
DNA in a
nucleus.
Amoeba and Yeast
How the microscope influenced the
cell theory?
The Invention of the Microscope helped the development of
the cell theory because it allowed the scientists to actually
discover that everything was made up of cells, and
what cells do to come up with that theory.
With the development and improvement of the light
microscope, the theory created by Sir Robert Hooke that
organisms would be made of cells was confirmed as scientist
were able to actually see cells in tissues placed under the
microscope.