Transcript Chapter 10

Chapter 9
Cell Growth and Division
Cell Growth
 When
a living thing grows, what happens
to its cells? Do they just get larger and
larger?
 An adult’s cells are about the same size as
a baby’s– there are just more of them
 As an organism grows, the cells get as
large as they can, and then they divide
and produce two new cells
Limits to Cell Growth
A
cell divides instead of continuing to grow
larger and larger. This is because there
are specific limits on cell growth
 DNA Overload: Imagine if the Media
Center only had 3 books. Would that be
enough for all the students at WHS? If the
cells get too large, then there isn’t enough
information, or DNA, to make the proteins
needed for life.
Limits to Cell Growth, Cont.

Exchanging Materials- Imagine 4 students in the
gym passing an egg back and forth to each
other. Is it easier or harder for these 4 students
in the gym or in Mrs. C’s classroom? If the cell
gets too big, food, gases and such cannot easily
travel through the cell
 Surface area and volume: The volume of the
cell grows faster than the surface area of the cell
membrane. There isn’t enough room on the
membrane to get enough stuff in and out of the
cell for the increasing volume– this can cause
major problems!
Solving These Issues
 Because
of DNA overload, exchanging
materials and surface area and volume, a
cell must divide in order to continue
working properly.
 This is called cell division, where one cell
divides into two “daughter cells” which are
genetically identical to the parent cell.
DNA is replicated before division, so each
cell gets their own copy of DNA
Cell Division

Chromosomes- DNA
and protein condense
to form chromosomes
which lives in the
nucleus and carries
the cell’s coded
genetic information
 Each chromosome is
made out of two sister
chromatids and
attached at the center
by the centromere
The Cell Cycle
 During
the cell cycle, a cell grows,
prepares for division and divides– and
then starts the cycle all over again
 Interphase– preparation for division.
Contains three parts, G1, S and G2
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G1- Cells increase in size
S- All DNA is replicated
G2- organelles and other molecules needed
for division are reproduced
The Cell Cycle, Cont.
 The
“M” Phase, known as Mitosis (division
of the nucleus)

Prophase- Chromatin condenses into
chromosomes and the centrioles separate.
Spindles form and the nuclear envelope starts
to break down
M Phase, Cont
 Metaphase-
Chromosomes line up down
center of the cell, each chromosome is
connected to a spindle fiber by the
centromere
M Phase, Cont
 Anaphase-
Sister chromatids separate and
are moved apart and start to travel to the
other side of the separating cell
M Phase, Cont.
 Telophase-
The chromosomes gather at
the opposite ends of the cell and lose their
distinct shapes. Two new nuclear
membranes form
M Phase, Cont.
 Cytokinesis-
the cytoplasm splits and two
new cells are formed. In plant cells, a cell
plate is formed.
Regulating the Cell Cycle
 Controls
on cell division include internal
and external regulators. Regulators don’t
allow the cell cycle to progress until all the
stages have happened OR tell the cell
cycle to stop so no more cells are made
 Internal- Cyclins are proteins that keep the
cell on the right track
 External– If a cell contacts another cell,
then the cells will stop making new ones
Uncontrolled Cell Growth

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Cancer is a disorder in which affected cells
continue to grow when they shouldn’t.
Cancer cells lack or have a defect in gene p53,
which normally halts the cell cycle when needed
Uncontrolled cell growth forms masses of
tissues called tumors
Cancer can be caused by: genetics, smoking,
chemicals, radiation exposure, certain viruses
Something that causes cancer is called a
carcinogen
Your assignment after notes
 Draw,
Label, Title and color the following:
 Page 244-245, figures 10-3 and 10-4
 Page 246-247, Figure 10-5
 Page 248 figure 10-6