Cell Structure And Function
All living things are made of the same basic building blocks, cells. A
human is
made of 65 trillion cells. Cells are everywhere, on you skin, in
your blood, and
even on your tongue. In fact, your blood is clear but red
blood cells are what
make your blood red. Most living things are made up of
many cells but some are
made of only one cell, like amebas, paramecium,
fungi, protists, monerans, and
bacteria. There are two basic types of cells,
animal cells and plant cells. They
have some common parts found in both and
other parts that are unique to each. A
cell membrane is found in both plant
and animal cells. It is the structure that
surrounds the cell and protects
it. Plant cells have a cell wall, a rigid
structure surrounding the cell
membrane. Animal cells do not have a cell wall.
Cytoplasm is the thick,
jelly-like substance that makes up most of the cell.
Vacuoles are fluid
filled sacs in the cell. The vacuoles contain stored water or
food that will
be used by the cell. Cells also contain other "small
organs" called
organelles that carryout various cell functions. And then
there is the
control center of the cell, the nucleus, surrounded by a protective
outer
covering call the nuclear membrane. The nucleus contains the DNA,
or
chromosomes, that carries all the instructions on how a cell will
function,
live, and reproduce. Every cell needs to energy to live and
reproduce. Plant and
animal cells obtain energy in different ways. Animals
can not make their own
food. They obtain energy by taking in food, water, and
oxygen and converting it
to sugar. Sugar is the only food a cell can eat.
Plant cells can make their own
food from water and sunlight. This process is
called photosynthesis. Both plant
and animal cells use energy from the food
they obtain to reproduce. All living
things produce more living things. Cell
reproduction is called mitosis. Mitosis
is the process of a single cell
dividing in two and then two more and so on. In
mitosis, the pairs of
chromosomes in the nucleus of the parent cell divide into
two daughter cells.
There are four phases of mitosis. In the first phase, the
chromosomes are in
a tangle and the nuclear membrane dissolves, or breaks apart.
In the
second phase, special fibers line up the chromosomal pairs. In the
third
phase, the fibers pull the pairs apart to opposite ends of the nucleus.
In the
final phase, the parent cell splits in two, creating two completely
new daughter
cells exactly like the parent cell. The two daughter cells will
grow and
eventually the process of mitosis will start again in each one. This
is how all
living things grow and continue. In closing, it is important to
remember that
all living things are made up of cells. Some have only one cell
while others
have very complicated systems of many cells working together.
Second, plant and
animal cells take in food, water, and oxygen in very
different ways, but both
need these substances to make the energy needed to
live, grow, and reproduce.
Finally, every cell passes on their DNA to
future generations through the
process of mitosis. The DNA, in both plant and
animal cells, contains all the
instructions needed for cell to grow and
function.