Cell Theory and Cells Parts

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Cell Theory and Cells Parts

• Chapter 2 continued

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The Cell TheoryThe first scientists to see
cells with his microscope was Robert Hooke. He
looked at cork cells. Even though he saw these
cells, he did not know how important the cells
actually were. In 1838, a scientist named
Matthias Schleiden looked at plant cells and
concluded that plants are made of cells.
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Theodor Schwann looked at animal cells and
concluded that animals are made of cells. They
both decided, based on what they saw, that all
living things are made up of cells. About 15
years later, Rudolph Virchow came up with the
cell theory.
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The cell theory states that 1. All organisms
are made up of one or more cells. 2. Cells
are the basic units of structure and function in
all organisms. 3. All cells come from cells
that already exist.
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How Cells are organizedCells have many things
in common. Some of these things are a cell
membrane, a cytoplasm and a control center.
There are two kinds of cells. They are
eukaryotic and prokaryotic cells. Prokaryotic
cells are cells that do not have a nucleus.
Eukaryotic cells have a nucleus. Plant and
animal cells are considered eukaryotic.
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Animal cell partsCell membrane the structure
that forms the outer boundary of the cell and
allows only certain things to move in and out of
the cell. Because of this, the cell membrane is
considered selectively permeable. It is also
very flexible. It is made of fat and protein.
It allows water, oxygen and food into the cell
and waste products out of the cell.
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The nucleus is the largest organelle in a cell.
The nucleus is a structure that directs the all
the activities of the cell. The nucleus is
protected from the cytoplasm by a nuclear
membrane. Materials move in and out of the
nucleus through openings. The nucleus also
contains hereditary material called chromatin.
These are the genetic blueprints for the
operations of the cells. When cells get ready to
divide, chromatin will begin to thicken and
become chromosomes.
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Cytoplasm a gel-like substance inside the cell
membrane and outside of the nucleus. It is
mostly made of water. It also holds all of the
other organelles that help the cell to run.
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Organelle the structures within the cytoplasm of
eukaryotic cells.
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Endoplasmic Reticulum also known as ER, it is
the folded membrane that moves materials around
in the cell. It extends from the nucleus to the
cell membrane. There are two types of ER, rough
and smooth. Rough ER is covered in ribosomes.
Ribosomes place where cells make their own
proteins. They receive direction from the
hereditary material in the nucleus about what
kind of protein to make. Ribosomes can either be
found on the rough ER or floating in the
cytoplasm.
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Another organelle in the cytoplasm is the Golgi
body. The golgi bodies are stacks of
membrane-covered sacs that package ad move
proteins to the outside of the cell.
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Cells also require energy. They get their energy
from the mitochondria. The mitochondria are where
food particles are broken down and energy is
released. The Mighty mitochondria releases
energy for the cell!!
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Cells are constantly producing waste products and
they need to get rid of the waste. The lysosomes
contain chemicals that digest wastes and worn out
cell parts and also break down food.
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Vacuoles are storage organelles. They are fluid
filled temporary storage areas. They can either
store water or food.
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Plant CellsAnimal and plant cells have all the
same organelles except for a few. Plants have
cell walls and chloroplasts. A cell wall is a
rigid structure outside of the cell membrane that
supports and protects the plant cell. It is made
of cellulose and other materials. Animal cells
do not have a cell wall.
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Plant cells also have chloroplasts. Chloroplasts
are organelles in plant cells in which light
energy is changed into chemical energy in the
form of sugar. The chemical in the chloroplasts
that capture the light energy is chlorophyll.
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Cells differ in the way that they look based on
what their job is in an organism. Nerve cells
look different than red blood cells and red blood
cells look different than white blood cells.
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Cells are organized in different ways. A one
celled organism performs all of its life
functions in itself. Cells in many-celled
organisms do not work alone. In many celled
organisms, cells are organized into tissues. A
tissue is a group of similar cells that work
together. Tissues are then organized into
organs. Organs are structures made up of
different tissues. Groups of organs combine to
make up organ systems and then organ systems make
up an organism.