Download chapter 9 cellular reproduction

CHAPTER 9 CELLULAR
REPRODUCTION
P. 243-257
SECTION 9-1
CELLULAR GROWTH
Page 244
ESSENTIAL QUESTION
 Why
is it beneficial for cells to
remain small?
MAIN IDEA
 Cells
grow until they reach their size
limit, then they either stop growing
or divide.
CELL SIZE LIMITATIONS
 Most
cells are smaller than a period at
the end of a sentence.
 There are two reasons cells divide rather
that continue to grow.
  The larger the cell becomes, the more
demands the cell places on it DNA.
  The larger the cell becomes, the more
trouble the cell has moving nutrients
and wastes across the cell membrane.
HOW DOES THE AMOUNT OF SURFACE AREA
CHANGE AS THE CELL’S VOLUME INCREASES?
RATIO OF SURFACE AREA TO
VOLUME
 The
key factor that limits the size of a cell
is the ratio of its surface area to volume.
  The surface area refers to the area
covered by the plasma membrane.
  The volume refers to the space taken by
the inner contents of the cell, including
the organelles in the cytoplasm and the
nucleus.
HOW DOES THE AMOUNT OF SURFACE AREA
CHANGE AS THE CELL’S VOLUME INCREASES?
RATIO OF SURFACE AREA TO
VOLUME
 As
a cell grows in size, its volume increases
faster than its surface area.
 This means the cell might have trouble
supplying and transporting nutrients and
expelling enough waste products.
 By remaining small, cells can sustain
themselves more easily.
CELL CYCLE
 Once
a cell reaches its size limit, it will
either stop growing or divide.
 Most cells divide. Nerve and muscle cells
do not divide.
 Cell division also is the way the cell
reproduces so that you grow and heal
certain injuries.
 Cells reproduce by a cycle of growing and
dividing called the cell cycle.
CELL CYCLE
 
3 main stages……..
  Interphase – cell grows, carries out
certain cellular functions, replicates
its DNA [3 substages]
  Mitosis – cell’s nucleus and nuclear
material, DNA, divide [4 substages]
  Cytokinesis – cytoplasm divides
CELL CYCLE
STAGES OF INTERPHASE
 G1
stage (normal cell growth) has the
longest duration.
 G1 - 1st stage, a cell is growing, carrying
out normal cell functions, and preparing
to replicate or copy DNA
 S - 2nd stage, cell copies its DNA in
preparation for cell division
  Chromosomes contain the genetic
material that is passed from one
generation to the next.
STAGES OF INTERPHASE
  Chromatin
is the relaxed form of DNA
in a cell’s nucleus.
 Chromatin
condenses or tightens to
form chromosomes.
 G2 - 3rd stage, Cell prepares for the
division of its nucleus.
  The
cell makes sure everything is ready
for mitosis.
 A
cell spends the majority of its
lifetime in interphase.
SECTION 9-2
MITOSIS AND CYTOKINESIS
Page 248
MAIN IDEA
 Eukaryotic
cells reproduce by mitosis, the
process of nuclear division, and
cytokinesis, the process of cytoplasmic
division.
MITOSIS AND CYTOKINESIS
PHASES OF MITOSIS - PROPHASE
 1st
phase - longest
 Chromatin tightens into chromosomes
that are X-shaped and become visible.
 Centrioles separate and move to opposite
poles of the cell.
 Nuclear membrane disintegrates.
 Nucleolus disappears.
 Mitotic spindle begins to form between
the poles.
CHROMOSOMES
PROPHASE
xxxx
xxxx
xxxx
PROPHASE
 Spindle
apparatus is made of spindle
fibers, centrioles, and aster fibers.
 The spindle apparatus is important
in organizing and moving
chromosomes before cell division.
 Plant cells do not have centrioles.
BY THE END OF PROPHASE, THE
FOLLOWING HAS OCCURRED:
 By
the end of prophase, the following
has occurred:
  Nuclear envelope seems to disappear.
  Spindle fibers attach to sister
chromatids on both sides of the
centromere.
METAPHASE
 2nd
phase - shortest
 Sister chromatids are pulled along the
spindle apparatus to center of cell and line
up in the middle.
 Tension of spindle fibers pulls them along.
METAPHASE
xxx
ANAPHASE
 3rd
phase
 The centromeres that join the sister
chromatids split.
 The sister chromosomes become
individual chromosomes.
 The two sets of chromosomes move
apart to opposite poles.
ANAPHASE
TELOPHASE
 4th
phase - last phase
 Chromosomes gather at opposite
ends of the cell and lose their shape.
 Two new nuclear envelopes form.
 Nucleoli reappear.
 Spindle apparatus comes apart.
TELOPHASE
CYTOKINESIS
 Cytokinesis
usually happens at the same
time as telophase.
 The cell membrane is pulled inward until
the cytoplasm is pinched into two nearly
equal parts.
 Results are two cells, with identical
nuclei.
 In plant cells, a cell plate forms that later
becomes cell wall to divide the cells.
CYTOKINESIS
SECTION 9-3
CELL CYCLE REGULATION
Page 253
MAIN IDEA
 The
normal cell cycle is regulated by
cyclin proteins.
CYCLINS
 In
a multicellular organism, cell growth
and cell division are carefully controlled.
 When an injury such as a cut in the skin
occurs, cells at the edge of the cut divide
rapidly.
 When the healing process is nearly
complete, the rate of cell division slows
and then returns to normal.
CYCLINS
 When
cells come into contact with one
another, molecules on their surface signal
them to stop growing.
 Cyclins, a group of proteins, regulate the
timing of the cell cycle in eukaryotic cells.
 Cyclins are one group of proteins involved
in cell cycle regulation.
 Other proteins, called regulatory proteins,
regulate the cell cycle in different ways.
CANCER
 Contols
on cell growth can be turned on
and off by the body.
 Cancer is a disorder in which some of the
body’s cells lose the ability to control
growth.
 Cancer cells do not respond to the signals
that control the growth of most cells.
 As a result, cancer cells divide
uncontrollably.
CANCER
 Cancer
cells reproduce rapidly because
they spend less time in interphase.
 Cancer cells do not stop growing when
they touch other cells.
 They continue to grow and divide until
their supply of nutrients is used up.
CANCER CAN BE CAUSED BY….
 Changes
that occur in the regulation of
cell growth and division of cancer cells are
due to mutations or changes in segments
of DNA.
 The changes can damage the control of the
proteins that regulate the cell cycle.
 The genetic change or damage can often be
repaired by various repair systems
 If repair systems fail, cancer can result.
CARCINOGENS
 Various
environmental factors can affect
the occurrence of cancer cells.
 Substances that are known to cause
cancer are called carcinogens.
 Examples: cigarettes, asbestos, X rays,
the Sun’s ultraviolet rays
APOPTOSIS
 Apoptosis
is programmed cell death.
 Cells going through apoptosis actually
shrink and shrivel in a controlled
process.
 Example: When hands and feet begin to
develop, there are cells between fingers
and toes that look like webbing.
 The webbing is not present in the
mature organism.
STEM CELLS
 Most
cells in a nulticellular organism are
designed for a specialized function.
 Stem cells are unspecialized cells that
can develop into specialized cells when
under the right conditions.
 Two basic types of stem cells:
  Embryonic- After a sperm terilizes an
egg, the resulting mass of cells divides
until there are about 100-150 cells.
STEM CELLS
  Adult-
Found in various tissues in the
body and might be used to maintain and
repair the same kind of tissue where
they are found.
 Researchers
think certain kinds of
adult stem cells might be able to
develop into different kinds of cells for
treatment of disease and conditions.