Transcript Cell Size Notes - Union High School

Cell Growth
Do Now:
Do organisms get larger when
they grow because each cell
increases in size or because it
produces more of them?
I. Why should cells divide?
A.
DNA overload
1. There is only one original copy of DNA
in each cell
2. If the cell gets too big, the DNA can
not serve it.
3. A small library can only serve a small
town. More people = the library needs
more books
B. Exchanging Materials
1. Food, O2, H2O into a cell, CO2 and
waste out through the cell membrane
2. If the cell is too big, not enough
nutrients will be moved in and too much
waste will build up.
3. There would not be enough surface
area for the increasing volume
II. Surface Area to Volume
A. Volume increases more rapidly than the
surface area.
Surface area = (length x width)(number of sides)
Volume = length x width x height
Surface area/volume = ratio
Figure it out…
III. Cell Division
A. Before the cell becomes too large:
1. It copies (replicates) it’s DNA
2. Divides into 2 equal and
identical
daughter cells
10-2
Cell Division
That first cell had all the information and
instructions to make you as you are now.
It was all in a secret code in the middle of
the cell.
This code is called DNA. It is a very long
list of instructions that gives each cell in
your body its own shape and function.
That first cell grew a little and then "wiggly" bits
called chromosomes could clearly be seen.
Half of the chromosomes came from the egg
cell, and half from the sperm cell and each
chromosome contained two copies of that secret
code, the plans to make you
 The first cell then divided into two separate cells
using a process called cell division and this is
how it happened...


First the chromosomes lined up in the
center of the cell.
Then each chromosome split into two
identical halves.
Next the cell made a fold down its middle
and...
HEY PRESTO!!!
Two cells, which both had all the
information and instructions to make
you...and then...
Those
cells grew a bit...
copied their chromosomes and
those
became
then
then became
then
then
then
then
became
You get the
idea…
Then:
Very soon there were
If one of your cells was really this size you'd
be as big as the Empire State Building in
America.
I. Chromosomes
A. Made of DNA and proteins
B. Invisible except during cell
division
(chromatinchromosomes)
C. Human cells have 46
carrot cells have 18
http://www.youtube.com/watch?v=Q6ucK
WIIFmg
 http://www.nobelprize.org/educational/me
dicine/2001/cellcycle.html
 http://www.youtube.com/watch?v=VRhz3
DhjG5M
 http://www.youtube.com/watch?v=jk2RJ
m5RBEk
 http://www.youtube.com/watch?v=z7I0m
w4ZDJA&list=PL07B5D7AF5D381E65
