Download Cell Cycle - cloudfront.net

Bell Work
Get
October 20, 2010
out journals
How does an organism grow?!
All Change is
a miracle to
contemplate;
but it is a
miracle taking
place every
second. –
Henry David
Thoreau
Cell Cycle
Do cells grow?
 Yes,
but just enough to have double of
what is needed.


Organelles, cytoplasm, membrane, etc
When we are babies we have fewer cells
than when we are adults. Our cells divide
and create more cells as we grow.
 All


cells are generally the same size.
A small plant and a large plant have the
same size cells.
The muscle tissue on an elephant and the
muscle tissue of a mouse have the same
size cells.
Why do cells have to divide?
 Because
growing too big has consequences.

Becomes less efficient in 3 ways…
1. DNA becomes overworked.

2. Small cells are much easier/faster to replicate.

3. The main consequence is that it is much harder
to move materials across the cell membrane.

 Surface
Area : Volume (ratio)
High Surface Area to Volume
Ratio
 Surface
Area/Volume (Look on Test)
 The smaller the cell is, the greater the
surface area to volume ratio.

This means there is more area for materials
to be transported through the membrane.
 What
the cell wants is a higher Surface
Area than the volume.
BUT…
 Volume increases faster than Surface
Area.
Cell Size
Surface Area
(length x width x 6)
Volume
(length x width x height)
Ratio of Surface
Area to Volume
What is the cell cycle?
 It
is the series of events that cells go
through in order to grow and divide.
 Called
a “cycle” because it is an
ongoing/continuous process.
3 Basic Types
 1.
Binary Fission in prokaryotes (Bacteria)
 2.
Cell division (Mitosis) in eukaryotes for
the purpose of growth and repair.
 3.
Cell division (meiosis)that produces sex
cells (gametes)
Prokaryotic Cell Division
 Relatively
simple…
 These cells reproduce through binary
fission.
 First: the genetic information is copied.
 Then the cell divides in two.
 Each new cell receives an exact copy of
the genetic information.
 These daughter cells are exactly identical.
Binary Fission
 Is

a type of asexual reproduction
Benefits
 Reproduce
quickly
 All information comes from one parent
 Same number of chromosomes as parent cell

Non-benefit
 Reduces
genetic variation
 Population cannot adapt as quickly
Eukaryotic Cell Division
2


distinct part to the Cell Cycle
1. Interphase (Between phase)
2. M Phase (Mitosis and cytokinesis)
Interphase

Resting Stage
 Looks like the cell is
resting.
 Majority of time is spent
here.
 DNA Chromatin

3 phases of Interphase
 G1 phase: the cell grows &
carries out routine functions.
(increase in size)
 2. S phase: chromosomes
are copied.
 Critical: because each
daughter cell needs a
complete set.
 The number of
chromosomes in cells is
constant within a species.
 Humans= 46
chromosomes or 23 pairs
 3. G2 phase: cell prepares
for nucleus to divide.
 Cell grows & produces
additional organelles &
cytoplasm.
M Phase
 Mitosis
 Division
of the nucleus to form two nuclei.
 Ensures each new cell gets a copy of
every chromosome.
 Takes the least amount time, but has the
most action.
Mitosis - General
Chromosomes have replicated & are visible
# of centromeres = # of chromosomes
Mitosis – General Cont’d
Each daughter cell receives its own copy of
the parent cell’s DNA
Occurs in body cells – somatic cells
Cytokinesis


Still a part of the M phase…but NOT a part of mitosis!
This is the division of the organelles and cytoplasm.
Disruptions in the cell cycle…
 We
are made up of many kinds of
specialized cells.
 Skin
cells, muscle cells, red blood cells, liver
cells, it goes on and on.
 Cell
divide to make other cells, like
themselves.


Cells continue to grow until they touch another cell.
The cell cycle is controlled by proteins call cyclins.
Continued…
 Disruptions
lead to diseases, such as…
 Cancer
 Causes
abnormal cells to form or an unusually large
number of cells to form.
 These cells do not respond to signals that regulate the
growth of most cells
 If these cells join together into a large mass, it is called
a tumor. And they grow at a faster rate.
 Many
 The
have a defect in a gene called p53.
cell cycle can be disrupted when…
 DNA
is not copied correctly.
 Environmental factors: radiation, tobacco smoke,
other pollutants. (mutagens)
Cancer
Loss of control during the cell cycle can lead to cancer
Cancer cells do not show contact inhibition and they divide uncontrollably
Can result from a single nucleotide change in the DNA!
Cancer Cells YouTube
1. In which phase of the eukaryotic cell cycle is the
genetic material duplicated?
A. G1 phase
B. 2nd- S phase
C. G2 phase
D. M phase (MITOSIS)
2. Which two phases of the cell cycle make up cell
division?
A. G1 & Cytokinesis
C. G2 phase & Cytokinesis
B. Interphase & mitosis
D. Mitosis & Cytokinesis