Download Chapter Five: Cell Growth and Division

Section One: The Cell Cycle
 Cell Cycle: the regular patter of growth, DNA
duplication, and cell division that occurs in eukaryotic
cells.
 4 Main Stages
1.
2.
3.
4.
Gap 1 (G1)
Synthesis (S)
Gap 2 (G2)
Mitosis (M)
Section One: The Cell Cycle
 Cell Cycle
 Gap 1 (G1)




Cell carry out normal
functions but increase in
size
Organelle number
increases
Stage the cell stays in the
longest
Must pass a checkpoint
before going into synthesis
Section One: The Cell Cycle
 Cell Cycle
 Synthesis (S)


The cell makes a copy of
its DNA
Cell contains two complete
sets of DNA
Section One: The Cell Cycle
 Cell Cycle
 Gap 2 (G2)


Cells carry out their
normal functions and
continue to grow
Checkpoint before Mitosis
Section One: Cell Cycle
 Cell Cycle
 Mitosis (M)


Includes mitosis and
cytokinesis
Mitosis: the division of the cell
nucleus and its contents


Nuclear membrane dissolves,
duplicated DNA condenses
around proteins and separates,
and two new nuclei form
Cytokinesis: the process that
divides the cell cytoplasm
resulting into two daughter
cells that are gentically
identical to the original cell
Section One: The Cell Cycle
 Cell Cycle
 Rates of cell division vary based on cell type, the needs
for that cell, and age
 Cell that divide rarely are said to be in the G0 stage
 Cell size is limited
Section Two: Mitosis and
Cytokinesis
 Chromosomes
 One long continuous thread
of DNA that consists of
numerous genes along with
regulatory information
 Human body has 46
chromosomes
 Must condense itself before
mitosis can begin


Allows them to divide evenly
during mitosis
DNA is loosely organized
during interphase to allow easy
access to genes so proteins can
be made
Section Two: Mitosis and
Cytokinesis
 Chromosomes
 At almost all times during
the cell cycle your
chromosomes are wrapped
around histones
 Histones: a protein the
organizes chromosomes
around which they are
wrapped



Looks like beads on a string
Helps to compact DNA
Chromatin: the loose
combo of DNA and proteins
Section Two: Mitosis and
Cytokinesis
 Chromosomes
 Futher condensing occurs
as mitosis gets closer and
closer
 Chromatid: one half of a
duplicated chromosome




Each chromosome was
copied during the S stage
Together the two chromatids
are called sister chromatids
They are held together at the
centromere
Telomeres: the ends of DNA
molecules that is made of
repeating nucleotides that do
not form genes
Section Two : Mitosis and
Cytokinesis
 Interphase and Mitosis
 Interphase


Duplication of organelles and DNA replication
One cell should have two full sets of DNA and be large enough
to divide
 Mitosis




Prophase
Metaphase
Anaphase
Telophase
Section Two: Mitosis and
Cytokinesis
 Mitosis
 Prophase




Chromatin condenses into
chromosomes
Nuclear envelope breaks
down
Centrioles move to
opposite sides (poles) of
the cell
Spindle fibers form
Section Two: Mitosis and
Cytokinesis
 Mitosis
 Metaphase


Spindle fibers attach to
each chromosome
They align the
chromosomes along the
center of the cell
Section Two: Mitosis and
Cytokinesis
 Mitosis
 Anaphase


Sister chromatids separate
and go to opposite ends of
the cell
Spindle fibers shorten
pulling the sister
chromatids apart
Section Two: Mitosis and
Cytokinesis
 Mitosis
 Telophase



Nuclear membranes start
to form
Chromosomes begin to
uncoil
Spindle fibers fall apart
Section Two: Mitosis and
Cytokinesis
 Cytokinesis: divides the cytoplasm into two cells and
completes the full stage of the cell cycle
 Animal cells: membrane forms a furrow that is pulled
inward by tiny filaments like a drawstring
 Plant cells: a cell plate forms between the two nuclei
Section Three: Regulation of the
Cell Cycle
 Cell Cycle Regulation
 Regulated by internal and external factors


External Factors
 Cell to cell contact
 Growth factors: group of proteins that stimulate cell division
 Hormones
Internal Factors
 Kinases and Cyclins
 Kinases transfer phosphate groups from one molecule to
another and are activated by cyclins
Section Three: Regulation of the
Cell Cycle
 Cell Cycle Regulation
 Apoptosis: programmed cell death


Internal and external signals activate genes that produce self
destructive enzymes
Ex. Webbing of fingers and toes
Section Three: Regulation of the
Cell Cycle
 Cancer
 Uncontrolled cell division
 Arises when regulation of the cell cycle breaks down
 Treated with chemotherapy or radiation
 Tumors form


Benign tumors: cancer cells stay clustered together and are usually
harmless
Malignant tumors: cancer cell break away, or metastasize, from the
tumor and spread to other parts of the body.\
 Carcinogens
 Substances known to produce or promote cancer
 Tobacco smoke and air pollutants
 Some are carried by viruses
Section Four: Asexual Reproduction
 Asexual reproduction
 The creation of offspring from a single parent and does
not involve joining sex cells
 The offspring are usually genetically identical to the
parent
 Binary Fission: type of asexual reproduction by dividing
into two roughly equal parts
Section Four: Asexual Reproduction
 Asexual Reproduction
 Advantages


Usually more efficient if the environment remains favorable
Less time and energy
 Disadvantages

No genetic variation
Section Four: Asexual Reproduction
 Asexual Reproduction
 Some organisms reproduce asexually through mitosis
 Ex. Cutting a stem off a plant and repotting it
 Can go through budding, fragmentation, or vegetative
reproduction
Section Five: Multicellular Life
 Multicellular Organisms
 Levels of Organization




Cell
Tissues: groups of cells that work together to perform a similar
function
Organs: groups of tissues that work together to perform a
similar function
Organ systems: groups of organs that carry out similar
functions
 Work to maintain homeostasis
Section Five: Multicellular Life
 Cell Specialization
 Cell differentiation: the
process by which
unspecialized cells
develop into their mature
forms and functions
 Stem Cells: a unique type
of body cell that has the
ability to divide and renew
themselves for a long
period of time, remain
undifferentiated in form,
and develop into a variety
of specialized cell types.
Section Five: Multicellular Life
 Stem Cell Types
 Adult



In the brain, liver, bone
marrow, skeletal muscle,
dental pulp, and fat
Also found in children
and umbilical cord blood
Can be taken out of a
patient and put back in
 Embryonic
 Come from donated
embryos grown in a clinic
 Can form any cell type in
the human body