Cells!
By: Ellie Hobelman
Cell Theory…
states that all living organisms have a basic unit of structure and
function, which is the cell.
This was a significant statement because it suggested that all living
things have a common denominator. Almost 200 years of
research by many different scientists led to this conclusion.
The initial discovery of cells was done by
Robert Hooke, an English scientist, in
1665.
Robert Hooke
designed one of the first microscopes and used it to look at plant
material. One specimen he examined was thinly sliced pieces
of cork. By look at the cork through the microscope, he
discovered that it was made up of many small units. Hooke
named these units cells.
Hooke
Hooke and other scientists observed other
samples of plant material and
discovered that they were also made up
of cells. As more and more material
was examined, scientists began to
recognize a pattern.
Matthias Schleiden, a German scientists in
1838
stated that all plant material was made up of cells.
Theodor Schwann
The following year, Theodor Schwann came to the same
conclusion about animals. Their findings are what
have become known as the cell theory.
Rudolf Virchow,
a German physician
suggested an adjustment to the cell theory. In 1858, he
suggested that the cell theory be changed to include
that all cells come from pre-existing cells.
Louis Pasteur
In the following years, experiments conducted by Louis Pasteur
provided the proof for Virchow’s proposal. Pasteur carried out
experiments to determine how milk curdled. Through
controlled environments, he proved that exposure to air
particles is what causes the change.
The “modern” Cell Theory
With the development of the electron microscope, the
theory has continued to evolve. As more living
material has been observed at higher magnifications,
much more has been learned about cells and cell
theory.
o
All living things are made up of cells
o
All cells arise from other cells
cells are capable of reproducing
themselves…
Parts of Cells…
All living things including plants
and animals
are made up of cells. Cells are made up of atoms, which are
smallest units of matter.
Parts of Cells
Surrounding the cell
Cell Wall
Most commonly found in plant cells & bacteria
Supports & protects cells
Cell Membrane
Outer membrane of cell that controls movement in and out of
the cell
Double layer
Inside the cell
Nucleus
Directs cell activities
Separated from cytoplasm by nuclear membrane
Contains genetic material – DNA
Nuclear Membrane
Surrounds nucleus
Made of two layers
Openings allow material to enter and leave nucleus
Cytoplasm
Cytoplasm
Gel-like mixture
Surrounded by cell membrane
Contains hereditary material
Ribosomes
Each cell contains thousands
Make proteins
Found on ribosomes & floating throughout the cell
Cell Movement…
Passive Transport: A cell continually exchanges
molecules and ions with its environment. When a
cell takes substances that are in greater
concentration outside the cell, the cell does not
need to expend energy. This is called passive
transport. It occurs by either facilitated diffusion or
simple diffusion.
Cell Movement…
Active Transport: For a cell to control its internal
environment, a cell must often extend energy to bring
substances into or out of the cell. Energy is required in
active transport.
Vocabulary…
Cell membrane- protective covering of the cell, controls
material coming in or out of the cell
Cytoplasm- gelatin-like material inside cell, work of cell
carried out here
Nucleus-contains the genetic material of the cell
Organelle- any part of the cell that is enclosed by
membrane
Cell wall- tough outer covering, outside the cell
membrane, only plants
Chloroplast- only in plants, organelle that use the
energy from sunlight to make sugar
Vocabulary…
Mitochondria- makes energy available to the cell
Golgi apparatus- package proteins
Lysosome- gets rid of waste in the cell
Vacuole- storage for the cell
Endoplasmic Reticulum (ER)- transports protein
through the cell
Ribosomes- protein synthesis takes place