Cells and the Cell Cycle
1. The Cell Theory
All
living organisms are composed of one or more cells.
Cells
are the basic units of structure and function in all organisms.
All
cells come from previously existing cells.
The
activity of an entire organism depends on the total activity of its independent
cells.
2.
Animal Cells vs. Plant Cells
See labeled diagrams of
the cell organelles.
See word search puzzle for
the functions of these organelles.
Centrioles
are found in ANIMAL cells ONLY!!
Cell
walls are found in PLANT cells ONLY!!
Chloroplasts
are found in PLANT cells ONLY!!
3.
The Cell Cycle
Why
Divide?
o
To
create a new organism (reproduction).
o
To
repair damaged tissues.
o
To
allow an organism to grow and develop.
o
To
keep the cell healthy
.
There
would not be enough exchange of materials through the cell membrane to sustain
the cells life if it continued to increase in size; the volume of the cell
increases faster than its surface area of the cell membrane.
If
the cell volume was too large, the nucleus could not relay important
information to the organelles quickly enough.
The
Nucleus
o
Science
experiments (involving removing and replacing cell organelles) proved that the
nucleus had to be present for the cell to fully function.
It coordinates, controls, and manages cell functions.
Stores all information and instructions for the organelles.
Genetic
Material
o
Chromatin
long skinny strands of
o
Chromosome
formed when the chromatin condenses inside the nucleus. Chromosomes form when the cell is preparing
to divide. Think about each spaghetti strand now wrapped tightly around
itself!
o
Gene
a segment of
The
cell cycle (ie. cell division) is made up of two parts: Interphase and Mitosis.
1) Interphase
o
During
interphase the cell grows, produces more organelles, and prepares for mitosis
by duplicating its chromosomes.
o
These
now duplicated chromosomes are called sister chromatids and are attached at the
centromere.
o
The
prefix inter means between (ie. interphase occupies the
time between every cell division).
2)
Mitosis
o
During
the division of a cell, it is the process that ensures that each new cell has a
nucleus with a complete set of instructions (DNA).
o
It
is the process by which genetic material, after being duplicated, divides into
two identical sets of chromosomes.
o
The
phases of Mitosis:
1.
Prophase the chromosomes (now
made up of two sister chromatids), shorten and thicken. The nuclear membrane dissolves.
o
Sister
chromatids Replicated forms of a chromosome joined together at the centromere.
2.
Metaphase the double stranded
chromosomes (sister chromatids) line up in the middle of the cell and form the metaphase plate.
o
Metaphase
Plate an imaginary line that is created when the sister chromatids line up in
the middle of the cell during the process of cell division.
3.
Anaphase the sister chromatids
are separated by spindle fibers and move to opposite poles of the cell. If anaphase proceeds correctly, each of the
daughter cells will have a complete set of genetic information.
o
Spindle
Fibers fibers that are responsible for physically ripping the sister
chromatids apart. In an animal cell, the other ends of the
spindle fibers are attached to the centrioles.
4.
Telophase the chromosomes reach opposite
poles of the cell and new nuclear membranes begin to form around each set. Cytokinesis begins
o
Cytokinesis
the dividing of the cytoplasm. The
cytoplasm separates into roughly two equal parts and the two daughter cells are
formed.
During
cytokinesis of an animal cell, we see
the formation of the cleavage furrow.
o
Cleavage
Furrow The region of an animal cell that pinches inward when the cell is in
the process of dividing. A shallow
groove forms in the cell surface near the old metaphase plate.
During
cytokinesis of a plant cell, we see
the formation of the cell plate.
o
Cell
Plate Small segments of the material that makes up the cell wall come
together in the middle of the dividing plant cell; these pieces will fuse and
form the new cell wall between the two daughter plant cells.