Download Parts of the Animal Cell

MAJOR PARTS OF THE CELL
A cell wall is a tough, usually flexible but sometimes fairly rigid
layer that surrounds some types of cells. It is located outside the
cell membrane and provides these cells with structural support and
protection, and also acts as a filtering mechanism. A major
function of the cell wall is to act as a pressure vessel, preventing
over-expansion when water enters the cell. They are found in
plants, bacteria, fungi, algae, and some archaea. Animals and
protozoa do not have cell walls.
Plasma Membrane. This is the outer boundary of the cell. It is made of phospholipids (fats) and cholesterol. Proteins are
embedded with in the membrane. These proteins allow certain
molecules to enter and exit the cell. The proteins and phospholipids
block many harmful molecules from entering the cell, but they will
allow important molecules such as oxygen and food molecules to
enter. Each cell must “breathe and eat”. If nothing could enter the
cell, then the cell would suffocate and starve. Just like you the cell
must be able to get rid of waste products such as carbon dioxide and
food waste. The proteins embedded in the plasma membrane allow
these waste products to exit without letting out nutrients the cell
needs to survive. The CARBOHYDRATES on the outside of the
cell are tags that identify the cell to other cells. They can also hold
out signs that tell the immune system that they have been invaded by
a disease and need to be destroyed by the immune system.
Nucleus:This is the largest organelle in the cell. It is
separated from the cytoplasm by a double phospholipid membrane (similar to
the plasma membrane) called the nuclear membrane. The cell’s DNA is
inside the nucleus. The DNA is packaged into 46 chromosomes. The nuclear
envelope is an extra layer of protection for the DNA from anything harmful
that might enter the cell. Since the DNA has all the instructions for the cell to
follow, the DNA must communicate with the rest of the cell. Large pores
within the nuclear membrane allow messenger molecules to enter and exit the
nucleus. These pores are guarded by proteins. The proteins will not allow the
DNA to exit and prevent many harmful molecules from entering.
The
nucleolus is a large factory that builds ribosomes. The ribosomes exit the
nuclear pores.
DNA:DNA stands for deoxyribonucleic acid. DNA controls all of the cells activities. The DNA sends out messenger proteins
that tell the cell what to do. Messenger proteins also report to the DNA about the cells activities. The cell would not know
what to do without the DNA. Every cell within an organism contains an identical set of DNA.
Endoplasmic Reticulum (ER):The ER looks like flattened sheets, sacs and
tubes of membrane. The ER surrounds the nucleus and extends into the
cytoplasm of the cell. The ER BUILDS lipids (fats) and membrane
proteins. The ER will also TRANSPORT these molecules to the place in the
cell they need to go next. The ER is divided into two parts. The ROUGH
ER and the SMOOTH ER. The Rough ER has RIBOSOMES studded on
the outer membranes of the ER. The ribosomes are what build large protein
molecules. The Smooth ER is smooth because it has no ribosomes on the
surface. This part of the ER builds large lipid molecules. When the lipids
and proteins are ready for transport they will be packaged into small
membrane bound vesicles that break off of the ER. Many times these
vesicles are headed to the GOLGI APPARATUS. (Look at next picture.)
Golgi Apparatus:The golgi apparatus is a system of stacked,
membrane-bounded, flattened sacs. The golgi apparatus modifies
macromolecules (large molecules) by adding or removing pieces to
make the final product. It will also sort macromolecules into groups
so they can be packaged and sent to different places. Some of these
packages are sent out of the cell. Some are sent to other organelles.
Membrane bound vesicles transport these macromolecules between
the flattened sacs of the golgi apparatus and to other parts of the cell.
These vesicles are formed by the golgi’s membrane.
Lysosomes: These are membrane-bounded vesicles that contain acid and enzymes that digest or break down intracellular
macromolecules. The macromolecules are broken down into their smaller molecular
components. They are then secreted (released) by the lysosome to be used by the cell
or sent out of the cell as waste. A few examples of enzymes found inside the
lysosome are protease, lipase, and nuclease. The enzyme protease breaks down
protein macromolecules. The enzyme nuclease breaks down nucleotides found in
DNA. The enzyme lipase breaks down lipids or fats.
Mitochondria: These organelles create all the energy for the cell. There are
many of these within each cell. Since an organism is a composition of cells,
all the energy needed for the organism comes from the mitochondria.
Chloroplasts – are plastids containing the pigment chlorophyll. Chlorophyll is
used during photosynthesis to capture light energy. That light energy is used to
break apart the chemical bonds of Carbon dioxide and water so the atoms can be
used to build sugar molecules. A group of plastids is called a thylakoid.