Download Cell Division

Cell Growth and Mitosis
Cell Growth
• Organisms grow by producing more cells
• Cell division occurs throughout an
organisms life
• Why do cells divide instead of just getting
bigger?
– Large cell = harder to move substances in
and out
– High Surface to Volume ratio
Surface/Volume
• S/V is the ratio of surface area to internal
volume
• A smaller S/V is more efficient for moving
substances in and out of a cell
• Cells stay small and divide to be more
efficient
Cell Cycle
• Time from the
beginning of
one division to
the beginning
of the next
Cell Cycle
• G1 phase – cell growth occurs
• S phase – DNA replication
• G2 phase – cell prepares for division,
special organelles produced
• M phase – cell division occurs
• G1, S, G2 are known as INTERPHASE
Mitosis
• Cells divide in a series of recognizable
stages known as mitosis
• Interphase (cell growth stage)
– Prophase
– Metaphase
– Anaphase
– Telophase
– Cytokinesis
Cell Division
Chromosome Anatomy
Prophase
• Centrioles move to
ends
• Mitotic spindles
form
• Chromosomes
become visible
• Nuclear membrane
breaks down
Metaphase
• Chromosomes line
up on the
metaphase plate
“equator” of the cell
• Spindle fibers
attach to
centromeres
Anaphase
• Chromatids begin
to pull apart
• Sister chromatids
begin moving to
opposite ends of
cell
Telophase
• Chromosomes
reach opposite
poles
• New nuclei form
• Chromosomes
unravel
Cytokinesis
• Cleavage furrow
forms
• Cell splits in two
• Nuclear membrane
reforms
Animation from: http://www.biologycorner.com/resources/mitosis-animated.gif