Transcript Cell growth, division, and reproduction

CELL GROWTH, DIVISION,
AND REPRODUCTION
Miller and Levine Biology
Sams
WHY DIVIDE?
• The larger a cell becomes, the more demands
the cells places on it’s DNA
• The larger a cell becomes, the less efficient it
becomes at moving nutrients in a wastes out.
WHY DIVIDE?
• Surface area is important to a cell because its
surface area is its membrane. Membrane is
responsible for nutrient/waste exchange.
• For a growing cell. A decrease in the relative
amount of cell membrane available creates
issues.
SURFACE/AREA VOLUME RATIO
CELL DIVISION
• Before becoming too large, a cell must divide.
This solves the problems of…
• increasing size by reducing cell volume
• Information overload by copying DNA
ASEXUAL REPRODUCTION
• Single celled organisms (i.e. bacteria) undergo
cell division as a sole means of survival.
• The two cells produced by this type of cell
division are genetically identical.
SEXUAL REPRODUCTION
• Involves fusion of two separate parent cells.
• Offspring produced by sexual reproduction
inherit some genetic information from each
parent.
ADVANTAGES/DISADVANTAGES
THE CELL CYCLE
• Cells go through a series of events known as
the “cell cycle” as they grow and divide.
• During the cell cycle, a cell grows, prepares for
division, and divides to form two daughter
cells.
BINARY FISSION
This type of cell division
is specific to single
celled organisms such
as bacteria.
EUKARYOTIC CELL CYCLE
• The eukaryotic cell cycle consists of four
phases: G1, S, G2, and M.
• The G1, S, and G2 phases are known as
interphase.
EUKARYOTIC CELL CYCLE
In G1, cells increase
in size and
synthesize new
proteins and
organelles. This is
where most of a
cell’s growth takes
place.
EUKARYOTIC CELL CYCLE
In the “S” phase,
new DNA is
synthesized as
chromosomes are
replicated. At the
end of this phase,
2X as much DNA
exists than there
was initially.
EUKARYOTIC CELL CYCLE
After replication, the
cell enters its
shortest phase
which is G2.
Organelles and
molecule required
for division are
produced.
EUKARYOTIC CELL CYCLE
The M phase, or
mitotic phase,
produces the
daughter cells. It
occurs in two
stages : mitosis
and cytokinesis.
• Mitosis is divided up into four stages
MITOSIS
• Prophase
• Metaphase
• Anaphase
• Telophase
Mitosis can last anywhere from a few minutes to
several days depending on the cell type.
PROPHASE
• Genetic material inside the chromosome
condenses as the nuclear envelope breaks
down
• Spindle begins to form outside nucleus
METAPHASE
• Centromeres of duplicated chromosomes line
up across the center of the cell
• Spindle fibers connect the centromere of
each chromosome to the two poles of the
spindle
ANAPHASE
• Chromosomes separate and move along the
spindle fibers to the opposite ends of the cell
TELOPHASE
• Chromosomes begin to spread out into a
tangle of chromatin
• Nuclear envelope reforms
CYTOKINESIS
• Cytokinesis completes the process of cell
division by splitting one cell into two
MITOSIS
CELL CYCLE REGULATION
• Not all cells move through the cell cycle at
the same rate
• Most of our muscle and nerve cells do not
divide once they’ve developed. However cells
of the skin and digestive tract divide rapidly
throughout life
CELL CYCLE REGULATION
• In “in vitro” experiments, cells will divide until
they come into contact with one another and
then stop.
• “In vivo”, cells divide rapidly immediately after
a wound forms but slow down when the
healing process nears completion.
CELL CYCLE REGULATION
• Cyclins are a family of proteins that regulate
the timing of the cell cycle in eukaryotic cells
CELL CYCLE REGULATION
• Internal regulators respond to events occurring
within the cell (i.e. proteins that regulate
events of the cell cycle)
• External regulators respond to events
occurring outside of the cell (i.e. growth
factors that stimulate or slow growth and cell
division)
CELL CYCLE REGULATION
• Unlike single celled organisms such as
bacteria, cells in our body sacrifice themselves
for the good of the “community”.
CELL CYCLE REGULATION
• Apoptosis is the process of programmed cell
death
CELL CYCLE REGULATION
CANCER
• Cancer is defined as a disorder in which body
cells lose the ability to control their growth
• Cancer cells do not respond to signals that
regulate the growth of most cells, resulting in
them dividing uncontrollably.
CANCER
CANCER GROWTH
1. A cell divides abnormally
2. The cancer cells produce a tumor which begins
to displace normal cells/tissues
3. Cancer cells may spread throughout the body
through bloodstream or lymph system. This is called
metastasis
CANCER TREATMENT
• Removal through surgery
• Treatment with radiation and/or radiation