THE CELL CYCLE
Chapter 10
Biology CPA
The
Cells
Life
of
Cycle
Wired Science Body Builders: https://www.youtube.com/watch?v=es9_7KuD9Io
CELL GROWTH
•A cell is limited by its cell size
•The larger the cell the harder it is to move
through tissue and get nutrients
•In order to stay alive and not grow continuously,
the cell will divide
REASONS WHY TO DIVIDE
•DNA
•Genetic information stored
•Found in the nucleus of the cell
•DNA would not be able to keep up with demand
of the cell
•Transport
•Rate decreases as the cell size increases
•Takes too long for nutrients and wastes to move
in and out of cell
SURFACE AREA TO VOLUME
•Surface Area
•Area on surface of cell where reactions can occur
•As a cell increases, the surface area decreases
CELL DIVISION AND REPRODUCTION
•Asexual Reproduction
•Produces identical offspring
from a single parent
•Used by many single-celled
organisms Ex: bacteria
•Occurs very quickly
•Sexual Reproduction
•Produces genetically different
offspring from two parents
•Fusion of two parent cells
CHROMOSOMES
•Made up of our DNA
•Holds genetic information
•Tight coils or rod like structures
•Organisms have a specific amount of
chromosomes
Humans have 46 chromosomes of DNA in every
somatic cell
CHROMOSOME STRUCTURE
•Histones are proteins that DNA wraps around to make the
chromosome shape
•Chromosomes are made of two sister chromatids
• Identical to each other
CHROMOSOMES
•Centromeres are in the center of a chromosome
•Chromosomes are tightly coiled strings of DNA called
chromatin
•Chromatin is the thin/string-like form of DNA
CHROMOSOME NUMBERS
•There is a specific number of chromosomes in
each organism
•Humans have autosomes and sex chromosomes
•We have 2 sex chromosomes
• Either X or Y
•We also have 44 autosomes
• Which do not code for gender
KARYOTYPE
•A karyotype
is a picture of one set of
chromosomes
• Shows you sex of organism
• Shows your any chromosomal disorders
CHROMOSOME NUMBERS
•A diploid cell contains 2 sets of each
chromosome
• Prefix di = 2
•A haploid cell contains only 1 set of each
chromosome
• Half of the total number
• Usually sex cells
CELL DIVISION IN PROKARYOTES
•Prokaryotes
• No nucleus
• No organelles
•Ex: Bacteria
•Reproduction is very fast
• Copy DNA
•Split into two cells
•Cell division is called binary fission
EUKARYOTIC CELL REPRODUCTION
•Eukaryotes
• Have a nucleus
• Have organelles
• Ex: Humans, plants
•Complex reproduction
• Everything needs to be controlled!
•Much slower process – about 18 hours!
CELL REPRODUCTION
A cell splits to make 2 identical
copies
If asexual reproduction
 Only 1 cell involved
This occurs in 3 main stages
1. Interphase – growth
2. Mitosis – division of the
nucleus
3. Cytokinesis – Splitting of the
cytoplasm
INTERPHASE
Cell growth and preparing
for division
INTERPHASE
•Cell growth
•Most of cell’s life is
spent in interphase
•3 Part of Interphase:
•G1, S, G2
G1 PHASE
•The cell is
growing
•The organelles
are duplicating
S PHASE
•Takes place when cells
are too big
•S = synthesis of DNA
•DNA is copied so there is
a set for each new cell
DNA REPLICATES IN INTERPHASE SO THE
DAUGHTER CELLS EXACT COPIES OF THE DNA
G2 PHASE
•Cell grows again
•Replication of
organelles
•Last stage of
interphase
•Cell prepares for
cell division
HOW IS DNA COPIED?
•Each cell has an protein called helicase
• Enzyme that “unzips” the DNA making 2 identical strands
• http://www.youtube.com/watch?v=zdDkiRw1PdU
• https://www.youtube.com/watch?v=JcZQkmooyPk
MITOSIS
Nuclear Division
MITOSIS
• The part of a cell’s life cycle when the
cell’s nucleus divides into 2 identical
nuclei
•4 steps:
•prophase
•metaphase
•anaphase
•telophase
PROPHASE
• All organelles disappear
• Centrioles separate and
move to opposite pole
• Chromatin becomes
chromosomes
• Centrioles shoot off spindle
fibers
METAPHASE
Chromosomes
line up at the
equator
(middle)
ANAPHASE
•Centromere splits
•Sister chromatids attach
to the short spindle
fibers
•Spindle fibers shorten
and bring the sister
chromatids to opposite
poles
TELOPHASE
•Chromatids become chromatin(one at each pole)
• Spindle disappears
•Organelles reappear
CYTOKINESIS
Cytoplasm Division
CYTOKINESIS
•Once mitosis has finished!
•Last stage of cell cycle
•Process is when the cytoplasm splits apart
•There are now 2 identical cells
CYTOKINESIS IN PLANT CELLS
•A cell plate forms between the two nuclei
•The cytoplasm divides
•A cell wall forms two daughter cells
CYTOKINESIS IN ANIMAL CELLS
•Cell membrane pinches in at equator
•Cleavage furrow
MITOSIS: DIVISION OF THE NUCLEUS
CELLS IN VARIOUS STAGES OF THE CELL
CYCLE
CONTROL OF CELL DIVISION
•Checkpoints (Regulatory Proteins)
•DNA repair enzymes will fix any mutations, if
checkpoint is passed division will occur
•Mitosis checkpoint – if all is correct, the 2
daughter cells will enter G1 phase and
interphase happens again
•If a cell does not meet requirements for
checkpoints, the cell will be programmed to die
Apoptosis is controlled cell death
Uncontrolled
Mitosis
is
cancer.
WHEN CONTROL IS LOST
•Enzyme proteins are not functioning
properly causing cell to reproduce
out of control
•Could cause cancer
•Cancer cells do not respond to
body’s regulators/cyclins that control
mechanisms
COMPARE/CONTRAST