Chapter 9
Cellular Reproduction
Why do cells need to reproduce?
Why are cells so small?
What is Surface Area?
How is the surface area represented in a cell?
What is Volume?
What happens when the volume of a cell increases?
Mini-Lab 9.1
Investigate Cell Size
Cell
Cell Size
Cell 1
0.00002 m
Cell 2
0.001 m
Cell 3
2.5 cm (0.025 m)
Cell 4
30 cm (0.3 m)
Cell 5
15 m
Cell Surface Area
(L x W x 6)
Cell Volume
(L x W x H)
Cell
Cell Size
Cell Surface Area
(L x W x 6)
Cell Volume
(L x W x H)
SA :V
Cell 1
0.00002 m 0.0000000024
0.000000000000008
300, 000 : 1
Cell 2
0.001 m
0.000006
0.000000001
6000 : 1
Cell 3
2.5 cm
(0.025 m)
0.00375
0.000015625
240 : 1
Cell 4
30 cm
(0.30 m)
0.54
0.027
20 : 1
Cell 5
15 m
1350
3375
1 : 2.5
Cell
Cell Size
Cell 1
0.002 cm
Cell 2
0.1 cm
Cell 3
2.5 cm
Cell 4
30 cm
Cell 5
1500 cm
Cell Surface Area
(L x W x 6)
Cell Volume
(L x W x H)
SA :V
Cell
Cell Size
Cell Surface Area
(L x W x 6)
Cell Volume
(L x W x H)
SA :V
Cell 1
0.002 cm
0.000024
0.000000008
3000:1
Cell 2
0.1 cm
0.06
0.001
60:1
Cell 3
2.5 cm
37.5
15.625
2.4:1
Cell 4
30 cm
5400
27000
0.2:1
Cell 5
1500 cm
13,500,000
3,375,000,000
0.004:1
Limits to Cell Size
Smaller cells can better:
1. Exchange nutrients and expel wastes across the
plasma membrane.
◦
higher surface area to volume ratio (SA:V)
Transport substances within the cell.
2.
◦
◦
diffusion
motor proteins along cytoskeleton
Communicate instructions for cellular functions.
3.
◦
signal proteins
Events of the Cell Cycle
The Cell Cycle
 The entire process of growing and dividing
 Repeated continuously
 Creates two cells from one cell
 Normal animal cells –
takes 12-24 hours
 3 main stages:
 Interphase
 Mitosis
 Cytokinesis
Stages of
Cell Cycle
• Interphase
• Includes G1, S, G2
 Followed by
Cell Division
 Includes Mitosis and Cytokinesis
Interphase
 Period of time during which the cell,
 grows and develops,
 carries out cellular functions,
 and makes copies of its DNA in preparation for cell
division
 3 parts (substages)
 G1 – Gap 1
 S – Synthesis
 G2 – Gap 2
Stages of
Interphase
 Gap 1 (G1)
 Immediately after cell divides
 Cell is growing and carrying out normal functions
 Cell is preparing to replicate DNA
 Synthesis Phase (S)
 Cell copies its DNA in preparation for cell division
 Gap 2 (G2)
 Cell prepares for division of its nucleus
 Makes proteins needed for cell division
Cell Division
 When a cell reaches its maximum size, the
nucleus initiates cell division.
 Cell division – the splitting of a single cell into
two cells.
‘Big Bang’ by M. Ormestad
©2006 All rights reserved
Cell Division
Cells divide so that an organism…
• can grow.
 increases mass of organism
 changes organism - differentiation
• can repair damaged cells and tissues.
 regeneration
 maintenance
• can reproduce.
Mitosis (Cell Division)
 Stage of cell cycle where the nucleus divides
 Includes four stages:
 Prophase
 Metaphase
 Anaphase
 Telophase
Cytokinesis (Cell Division)
 Process where the cell’s cytoplasm divides and creates
a new cell
Chapter 9.2
Mitosis and Cytokinesis
Mitosis & Cytokinesis
 Mitosis
 the cell’s nuclear
material divides
 4 parts (substages)
 Cytokinesis
 the cell cytoplasm
is divided into two
daughter cells
Genetic Material in the Cell
 Question 1: In what stage of the cell cycle is the
DNA copied?
 Answer 1: Synthesis
 Question 2: Why is this important?
 Answer 2: It prepares the cell for cell division
 Question 3: How is DNA organized in a cell?
 Hint:
 Answer:
 Chromosomes
Chromosomes
 Structures that contain
the genetic material of
an organism
 Only visible during
mitosis
 Formed when
chromatin is wound
tightly around proteins
 The DNA strands wraps
around proteins called
histones
 The continue to wrap
around forming
nucleosomes
 For most of the cell’s life, the DNA is contained in the
chromatin state
 In cell division, chromatin organizes into distinct
chromosomes structures
Chromosome Formation http://www.youtube.com/watch?v=gbSIBhFwQ4s
Chromosome
Structure
Centromere
• Structure where the
sister chromatids are
attached
Sister chromatids
• Identical copies
• Copies created during synthesis of
interphase
• Attached at beginning of mitosis
Stages of Mitosis
 Prophase
 Metaphase
 Anaphase
 Telophase
Human cell undergoing cytokinesis from M. Pines, Inside the Cell: The New
Frontier of Medical Science. U.S. Dept. of Health, Education, and Welfare,
1978.
Prophase
 1st stage
 longest
 Chromatin condenses into
chromsomes
 Nuclear membrane disintegrates
 Nucleolus disappears
 Chromosomes attach to spindle
apparatus
End of Prophase
• Spindle apparatus forms
• Spindle fibers
• Centrioles
• Chromosomes attach to
spindle fibers
Metaphase
 2nd stage
 shortest
 sister chromatids pulled
along the spindle
apparatus toward the
center of the cell
 line up along the middle, or
equator
Anaphase
 3rd stage
 sister chromatids are pulled apart
 spindle shorten
 separates chromatids into two identical sets
Telophase
 4th & last stage
 “opposite of prophase”
 Chromosomes arrive at poles of
spindle apparatus
 decondense
 Nuclear membrane and nucleolus
reform
 Spindle apparatus is broken down or
recycled
 May occur simultaneously with
cytokinesis
Another Look at Mitosis
Cytokinesis
 Division of the cytoplasm into two daughter cells
 Animal cells
 microfilaments constrict
 cell membrane pinches cell in two
 Plant cells
 construct a cell plate
 new cell wall forms on either side of cell plate
 Prokaryotic cells
 DNA copies attach to plasma membrane
 plasma membrane grows and pulls DNA copies
 cell membrane pinches into two cells
apart
Mitosis in Motion
 http://www.johnkyrk.com/mitosis.html
 http://www.cellsalive.com/mitosis.htm
 http://www.sci.sdsu.edu/multimedia/mitosis/navigator.html
 http://www.sumanasinc.com/webcontent/animations/content/
mitosis.html
Chapter 9.3
Cell Cycle Regulation
Normal Cell Cycle
 In eukaryotic cells, cell division driven by
 A protein cyclin binding to an enzyme
cyclin-dependent kinase (CDK)
Normal Cell Cycle
 Different cyclin/CDK combinations control different
activities in the cell cycle:
 Signals the start of the cell cycle during G1
 Signals DNA replication
 Signals protein synthesis
 Signals nuclear division
 Signals the end of the cell cycle
Normal Cell Cycle
 The cell cycle also has checkpoints to monitor the cycle and
stop it if something goes wrong
Abnormal Cell Cycle: Cancer
 Cancer is uncontrolled cell growth that occurs when there
is a failure in the regulation of the cell cycle
 Cancer cells crowd out other normal cells and can intrude
other organs; may lead to death of the organism from loss of
tissue
Abnormal Cell Cycle: Cancer
 Cancer cells occur when
mutations takes place in
segments of DNA
 Mutation cause changes in the
productions of proteins,
including cyclins
 Substances that cause cancer
are carcinogens
Apoptosis
 Normal, Programmed cell death
 Occurs in cells that are damaged beyond repair
 Can help protect cells from cancer
Stem Cells
 Cells are designed for
specialized functions
 Stem cells are
unspecialized cells that
can develop into
specialized cells
 Two types of stem cells:
 Embryonic
 Adult
Stem Cells
 The Nature of Stem Cells
 http://learn.genetics.utah.edu/content/tech/stemcells/scintro/
 Go, Go Stem Cells
 http://learn.genetics.utah.edu/content/tech/stemcells/sctypes/