Remember….
• Cell Theory1. All living things are composed of one or
more cells.
2. The cells is the basic unit of structure.
3. All cells come from preexisting cells.
Cell Theory #2 In Detail
• ORGANIZATION of LT
– Cells -> Tissues
– Tissues organize into
organs
– Multiple organs work
together to for an organ
system
– All systems work together
for survival of the organism
Why does a cell need to divide?
IN GENERAL• All organisms grow and change
• Worn-out tissues are repaired or are replaced by
newly produced cells.
Why does a cell need to divide?
SPECIFICALLY: Cell Size Limitations
1. Diffusion: short distances = efficient; long
distances = inefficient
• Think running 1/4mi vs. running 24 mi.
2. DNA: must be copied and made into protein to
make necessities…can only be done so fast.
• Think about copying homework for 1 class in
5 minutes vs. 7 classes in 5 minutes
3. Surface Area-to-Volume ratio: volume will become
to much for the PM’s surface area to handle.
• Think about a city growing, but no one builds new
roads or bridges etc.= traffic jam
http://openlearn.open.ac.uk/file.php/2815/S324_1_009i.jpg
A Cell’s Life – Describe the cell cycle
The Cell Cycle
1. Interphase – Longest Part of Cycle
–
–
–
“Growing Stage” - cell grows (G1, S, G2)
carries on metabolism, spends most of its time
here. (G1, S, G2)
DNA is copied (S only)
A Cell’s Life – Describe the cell Cycle
2. Mitotic Phase
a.) Mitosis : chromosomes divide
b.) Cytokinesis: cytoplasm divides into 2
HONORS
• Chromatin - long strands of DNA wrapped
around histones.
• Must copy DNA
• Supercoil to form chromosomes composed of
two halves called sister chromatids: exact copies of
each other held together by centromeres
micro.magnet.fsu.edu/ cells/nucleus/images/chr...
How do cells reproduce/divide?
a.) MitosisI. Prophase –
–
–
–
longest phase
Sister chromatids join
Nucleus (envelope and nucleolus)
disintegrate
mg.sparknotes.com/
8.2 Cell Growth and Reproduction
Mitosis cont’
II. Metaphase –
–
Chromosomes pulled to the
equator (middle)
mg.sparknotes.com/
8.2 Cell Growth and Reproduction
Mitosis cont’
III. Anaphase– Chromosomes split and sister
chromatids are pulled apart to
opposite poles of the cell
mg.sparknotes.com/
8.2 Cell Growth and Reproduction
IV. Telophase– Chromatids reach the
opposite poles (ends),
What is Cytokinesis?
b.). Cytokinesis - cytoplasm divides,
cells separate into two daughter cells.
mg.sparknotes.com/
Honors: What is cytokinesis?
• Animal cells: plasma membrane
pinches in along the equator
• Plant cells: a cell plate is laid
down across the cell’s equator
and a cell membrane forms
around each cell. New cell walls
form on each side of the cell
plate until separation is
complete
What is the end result of Mitosis?
• Two identical cells that are identical to the original
parent cell.
– will carry out the same cellular processes and functions as
those of the parent cell
– will grow and divide too
Specifically • Unicellular organisms = doubled number of organisms.
Called asexual reproduction
• Multicellular organisms = growth = more tissue.
Can you find all the stages?