Cell Growth & Division
Do now:
Who has
bigger cells?
Do Now:
Which has larger cells, a
mouse or an elephant?
CELLS
ARE
SMALL!
Why do we need to
make more cells?
From One Cell to Many
Sea Urchin
Cell Division
Why do we need to make more cells?
Why are we one
hundred trillion SMALL
cells and not one
hundred LARGE cells?
100,000,000,000,000 cells because....
I. Why do Cells Divide?
A. Cells need to stay small
because:
– The larger a cell becomes, the more
demands on its DNA
– Better organization
– Needs to move nutrients and wastes across
the cell membrane quickly
– If too big, cannot get nutrients fast enough
• DNA is the cell’s “library” of information.
• Imagine a very large city using one local
library for all materials
A big bag is weaker, harder to find things
Large cell,
difficult to
maneuver
organelles
More volume = bigger need
The larger the volume of
the balloon, the weaker it
is. The balloon skin stays
the same.
B. What is Surface area?
The total area of the surface
of a 3D object
What is the surface
area of this cube?
2 cm
2 cm
24 cm2
*Large surface area SPEEDS UP the movement of
materials*
C. What is Volume?
The amount of 3-D space that an
object occupies, “capacity”
*Large volume SLOWS down
movement of materials*
What is the
VOLUME of the
shape here?
200 cm3
cm
• As the length of cell increases,
volume increases faster surface area
(cm3 compared to cm2)
• HIGH ratio desired: quick movement of
materials
• Ex: 6000/1 is better than 2/1
It’s better to have lots
of small cells
instead of fewer
large cells!
A. All genes located in DNA in nucleus of
eukaryotic cell
B. Chromosomes
are condensed
forms of DNA
C. Chromosome number is unique to
every species
•
•
•
•
Humans: 46 chr.
Chimpanzees: 48 chr.
Yeast: 32 chr.
Adders-Tongue Fern: 1440 chr.!
How is DNA Packaged?
• Chromosome- when chromatin coils for
Mitosis
A.
46 chr
46
chromosomes
46 chr
B. Chromosome # stays the same
(Cells growths, doubles chromosomes, then splits,
forming two daughter cells with original # of
chromosomes)
•
•
•
•
Intestinal lining- every 24 hours
Skin
Blood cells/bone marrow- 120 days
Liver- sometimes
•
•
•
•
Muscle Cells
Cardiac cells
Kidney
Nerve cells
A. Interphase: “I-ball” 90% of the time!
Gap0
“resting phase”, cell is not growing
Gap1
cell grows, doubles organelles
Synthesis duplication of the DNA in
the cell's chromosomes
Gap2
cell grows, microtubules assembled
Prophase- “pasta”
• Chromatin fibers condense
• Nuclear membrane breaks down
• Spindle of microtubules forms from centrioles [animals
only]
• Attach to chromatids on centromere
Metaphase- “middle”
• Chromosomes line up in the middle
• Spindle fibers attach centrioles to
centromeres
• Every sister chromatid has fiber attached to
it
Centriole
Spindle
Anaphase: “away phase”, form “A’s”
• Spindle fibers contract
• Pull sister chromatids apart
• The chromosomes continue to move until they
are in two groups
• Each side has own copy of DNA
Individual
chromosomes
Telophase- “end phase”
• Nuclear membranes reform at each pole
• Chromosomes unwind
• Spindle disappears
C. CYTOKINESIS
During cytokinesis, the cytoplasm cuts
in half
A structure known as the CELL PLATE forms
midway between the divided nuclei.
Animal cells contract across middle of cell and
“pinch” making a “cleavage furrow”.
Twilight STUDIES IT TOO!
Parent
Cell
MITOSIS
Video Daughter
Cells
A. Spindle: network of microtubules that move
chromosomes during mitosis and meiosis
B. Equator: center line of cell where
chromosomes line up during metaphase
C. Poles: the opposite ends of cell
D. Centrioles: animal cells only, move the
spindle and chromosomes during division
E. Centromere: region where two sister
chromatids are joined tightly together
A. Production of 2 new daughter cells
B. Daughter cells are exactly the same
as original parent cell
C. Cell --> Tissue --> Organ --> Organ
System --> Organism
D. This is how organisms grow & develop!