Transcript Cell Cycle - Cloudfront.net

Notes Chapter 10
Cell Growth and
Division
Why do cells divide rather than
continuing to grow indefinitely?
Cell
growth…
- the larger a cell becomes, the more
demands the cell places on its DNA
and the more trouble it has moving
enough nutrients and wastes
across the membrane.
The volume and mass of a cell increases
much more rapidly than the surface
area…causing the ratio of surface area
to volume (or mass) to decrease.
 “Small
town” getting larger…
- not enough books in library
(information – DNA)
- has only a 2 lane main street
(more traffic means slower
movement)
Cell Cycle:
cell growth and division – separating
the cell contents into 2 equal parts
Before a cell become too large… it
divides, forming two daughter cells.
Cell Cycle
Before a cell divides… it must duplicate it’s
genetic material…
chromosomes
 Made
of DNA (which carries the
genetic code) and protein

Chromosomes are not visible except
during cell division …otherwise the DNA
and proteins are spread throughout the
nucleus

At the beginning of cell division,
chromosomes condense and are visible
chromatid
 One
of 2 identical “sister” parts of
a duplicated chromosome
centromere
 Area
where the chromatids of a
chromosome are attached
Quick Quiz

What is this called?

What is each
individual “side”
called?

What is the point of
attachment called?
Student Activity
You are going to make a Cell Cycle flip
book.
You’ll need 3 sheets of paper.
(We’re only using 3 sheets of paper… not 4.)
Staple twice at the top… near the crease.
Flip Book Cont…

At the bottom edge of the top paper…
write “Interphase”. You are going to draw a
picture and take notes about interphase on
this top page.
interphase
 An
“in-between” period of the cell
cycle that separates each division
of the cell

Interphase - the longest phase of the cell
cycle

Has three phases:
 G1
S
– cell growth
– DNA replication (and proteins)
– preparation for mitosis – shortest phase of
interphase – many organelles and molecules
needed for cell division are produced.
 G2
mitosis
 Process
of cell division... Dividing
a cell’s nucleus.
Flip Book Cont…
At the bottom of the second page… write
“Prophase”.
 You are going to draw and take notes
about Prophase on the second page.

prophase
•
Longest phase of mitosis (50% to
60% of time of mitosis)
•
Chromosomes become visible.
•
Centrioles separate and take up
positions on opposite poles (NOT
in plants).
•
Spindle fibers (microtubules that
help separate chromosomes) are
formed.
•
Nucleolus disappears and the
nuclear envelope breaks down.
•
http://www.cellsalive.com/mitosis.h
tm
Flip Book Cont…

At the bottom of the third page… write
“Metaphase”.
metaphase

Chromosomes line up
across the equator of the
cell (middle).

Microtubules connect the
centromere of each
chromosome to the 2
poles of the spindle.

http://www.cellsalive.com/
mitosis.htm
Flip Book Cont…

At the bottom of the fourth page write
“Anaphase”.
anaphase

Centromeres that join the
sister chromatids split.

Sister chromatids
separate.

Chromosomes move until
they separate into 2
groups near the poles.
http://www.cellsalive.com/mi
tosis.htm
Flip Book Cont…

At the bottom of the fifth page write
“Telophase”.
telophase

Chromosomes, that were
condensed and distinct,
begin to disperse
(disappear).

Nuclear envelope re-forms
around cluster of
chromosomes.

Spindle breaks apart.
http://www.cellsalive.com/mito
sis.htm
Flip Book Cont…

At the bottom of the sixth page write
“Cytokinesis”.
cytokinesis
 Division
of the cytoplasm
Animal vs Plant
daughter cells
Cell Division Overview

http://www.cellsalive.com/mitosis.htm

http://www.johnkyrk.com/mitosis.html
http://web.grcc.edu/biosci/pictdata/mitosis/pl
anmito.htm
Cell Cycle Overview
http://www.cellsalive.com/cell_cycle.htm
Mitosis Overview
Regulating cell division…
cyclins – proteins that regulate the timing of the
cell cycle (p. 250-251)

When an injury such as a cut in the skin occurs,
cells at the edge of the cut will divide rapidly.

When the healing process nears completion, the
rate of cell division slows down and then returns
to normal.
Uncontrolled cell growth…
cancer – a disorder in which some of
the body cells lost the ability to
control growth
 Cancer
cells
do not respond
to the signals
that regulate
the growth of
most cells…
Cancer cells divide uncontrollably and
form tumors.
Cancer cells may break loose from
tumors and spread throughout the
body.