Transcript Cell growth and division powerpoint

Cell Growth and Division
When we grow up, what’s
really happening to our cells?
Cell Growth and Division
Do we grow by getting
more cells?
Or do the cells we already
have get bigger?
Cell Growth
• Cells can only grow to a
certain size before they
have to divide.
• An adult and a baby have
the same size of cells.
Adults just have more cells.
• Your body makes about
24,000,000,000 new cells
each day.
Life is made of
cells video
Why can’t cells just get bigger?
There are two reasons
that cells have to
divide as they grow.
1- DNA overload
2- Exchanging materials
DNA Overload
• The bigger cells
get, the harder it
is for DNA to be
used by the entire
cell.
• Like a small town
library as the
town grows
bigger.
Exchanging materials
• The cell membrane
has to transfer items in
and out of the cell.
• As the cell grows, the
volume increases
faster than the surface
area does.
• Like the roads leading
into or out of a town.
The cell cycle
• The cell cycle (life
cycle of a cell) has 4
main parts:
–
–
–
–
G1 phase
S phase
G2 phase
M phase
The cell cycle
• Anytime the cell is not
dividing, it is in
Interphase
– During interphase the
cell grows, copies its
DNA, and gets ready
to divide.
• M phase is when the
cell divides
Cell Division
• During cell division
the cell actually
divides into two
identical cells.
Mitosis
• Mitosis has 4 parts:
1- Prophase
2- Metaphase
3- Anaphase
4- Telophase
1- Prophase
• During Prophase:
– Chromosomes
condense and
become visible.
1- Prophase
– Centrioles
move to
the poles of
the cell.
1- Prophase
– The nuclear
envelope breaks
down.
2- Metaphase
• During Metaphase,
the chromosomes line
up across the center of
the cell.
3- Anaphase
• During anaphase, the
chromosomes split
apart and move to
opposite sides of the
cell.
• Anaphase continues
until the chromosomes
stop moving.
4- Telophase
• Chromosomes begin
to disperse into a
tangle of chromatin.
• The nuclear envelope
reforms around the
two sets of chromatin.
Mitosis
• Mitosis is now
complete!
• Remember:
Mitosis:
1- Prophase
2- Metaphase
3- Anaphase
4- Telophase
Quiz time!!!
Which part of mitosis does each of the
following pictures represent?