Download Cell Growth and Division

Cell Growth and Division
Chapter 10
P 272- 301
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Chap 10: Cell Growth and Division 2009
Cell Division
About 2 trillion cells- about 25 million cells per
second- are produced by an adult human
body every day. All cells come from the
division of preexisting cells. (cell theory) Cell
division or reproduction is the process by
which cells produce offspring cells. Cell
division differs in prokaryotes and eukaryotes.
Cell reproduction in both prok and euk
produce the same result – two cells from
one!!
Biology notes-Chapter 8
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Review
What are the three parts to the cell theory?
1. All living organisms are composed of one or more
cells.
2. Cells are the basic units of structure and function in
an organism.
3. Cells come only from the reproduction of existing
cells.
Four things common is all cells:
cell membrane, cytoplasm, DNA, ribosomes
Biology notes-Chapter 8
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How does a cell produce a new cell?
10.1- Why do cells Divide?
10.2- How do cells Divide?
10.3- How does a cell control the process of cell
division?
10.4- How does a single undifferentiated cell
lead to a complex multicellular organism?
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Chap 10: Cell Growth and Division 2009
Voc Terms 10.1- 10.2
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Cell Division
Asexual reproduction
Sexual reproduction
Chromosomes
Chromatin
Cell cycle
Interphase
Mitosis
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Cytokinesis
Prophase
Centromere
Chromatid
Centriole
Metaphase
Anaphase
telophase
Chap 10: Cell Growth and Division 2009
THINK ABOUT IT –
Limits to Cell Size
1. When a living thing grows, what happens
to its cells?
2. What is there about growth that requires
cells to divide and reproduce themselves?
What are some of the difficulties a cell faces
as it increases in size?
The larger a cell becomes, the more demands
the cell places on its DNA. In addition, a
larger cell is less efficient in moving
nutrients and waste materials across its
cell membrane.
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Chap 10: Cell Growth and Division 2009
Information “Overload”
– Living cells store critical information in DNA.
– As a cell grows, that information is used to
build the molecules needed for cell growth.
– As size increases, the demands on that
information grow as well. If a cell were to grow
without limit, an “information crisis” would
occur.
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Chap 10: Cell Growth and Division 2009
Information “Overload”
–
Compare a cell to a
growing town. The town
library has a limited
number of books. As the
town grows, these
limited number of books
are in greater demand,
which limits access.
–
A growing cell makes
greater demands on its
genetic “library.” If the
cell gets too big, the
DNA would not be able
to serve the needs of
the growing cell.
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Chap 10: Cell Growth and Division 2009
Exchanging Materials
– Food, oxygen, and water enter a cell through the cell
membrane. Waste products leave in the same way.
– The rate at which this exchange takes place
depends on the surface area of a cell.
– The rate at which food and oxygen are used up and
waste products are produced depends on the cell’s
volume.
– The ratio of surface area to volume is key to
understanding why cells must divide as they grow.
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Chap 10: Cell Growth and Division 2009
Ratio of Surface Area to Volume
– Imagine a cell shaped like a cube. As the
length of the sides of a cube increases, its
volume increases faster than its surface area,
decreasing the ratio of surface area to
volume.
– If a cell gets too large, the surface area of
the cell is not large enough to get enough
oxygen and nutrients in and waste out.
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Chap 10: Cell Growth and Division 2009
Traffic Problems
–
To use the town analogy
again, as the town grows,
more and more traffic clogs
the main street. It becomes
difficult to get information
across town and goods in
and out.
–
Similarly, a cell that
continues to grow would
experience “traffic”
problems. If the cell got too
large, it would be more
difficult to get oxygen and
nutrients in and waste out.
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Chap 10: Cell Growth and Division 2009
Division of the Cell
– Before a cell grows too large, it divides into two
new “daughter” cells in a process called cell
division.
– Before cell division, the cell copies all of its DNA.
– It then divides into two “daughter” cells. Each
daughter cell receives a complete set of DNA.
– Cell division reduces cell volume. It also results
in an increased ratio of surface area to volume,
for each daughter cell.
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Chap 10: Cell Growth and Division 2009
Cell Division and Reproduction
How do asexual and sexual reproduction
compare?
– The production of genetically identical offspring
from a single parent is known as asexual
reproduction.
– Offspring produced by sexual reproduction
inherit some of their genetic information from
each parent.
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Chap 10: Cell Growth and Division 2009
Asexual Reproduction
– In multicellular organisms, cell division leads
to growth. It also enables an organism to
repair and maintain its body.
– In single-celled organisms, cell division is a
form of reproduction.
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Chap 10: Cell Growth and Division 2009
Asexual Reproduction
– Asexual reproduction is reproduction that involves
a single parent producing an offspring. The offspring
produced are, in most cases, genetically identical to
the single cell that produced them.
– Asexual reproduction is a simple, efficient, and
effective way for an organism to produce a large
number of offspring.
– Both prokaryotic and eukaryotic single-celled
organisms and many multicellular organisms can
reproduce asexually.
– -Bacteria cells reproduce by binary fission
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Chap 10: Cell Growth and Division 2009
Sexual Reproduction
- In sexual reproduction, offspring are
produced by the fusion of two sex cells – one
from each of two parents. These fuse into a
single cell before the offspring can grow.
– The offspring produced inherit some genetic
information from both parents.
– Most animals and plants, and many singlecelled organisms, reproduce sexually.
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Chap 10: Cell Growth and Division 2009
Cell Division -Eukaryotes
Two main types of division:
1. Mitosis- results in new cells with genetic material
that is identical to the genetic material of original
cell
During: growth, development, repair, asexual
reproduction (production of offspring from one
parent)
2. Meiosis- occurs during the formation of gametes
(reproductive cells, 1n), reduces the chromosome
number by ½ in new cells, often combine to make
2n cells
Biology notes-Chapter 8
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Comparing Sexual and Asexual
Reproduction
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Chap 10: Cell Growth and Division 2009
8.2- THINK ABOUT IT
1. What role does cell division play in your life?
2. Does cell division stop when you are
finished growing?
What is the role of chromosomes in cell
division?
–
Chromosomes make it possible to
separate DNA precisely during cell division
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Chap 10: Cell Growth and Division 2009
Chromosomes
– The genetic information that is passed on from
one generation of cells to the next is carried by
chromosomes.
– Every cell must copy its genetic information before
cell division begins.
– Each daughter cell gets its own copy of that
genetic information.
– Cells of every organism have a specific number of
chromosomes.
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Chap 10: Cell Growth and Division 2009
Prokaryotic Chromosomes
– Prokaryotic cells lack nuclei. Instead, their
DNA molecules are found in the cytoplasm.
– Most prokaryotes contain a single, circular
DNA molecule, or chromosome, that
contains most of the cell’s genetic information.
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Chap 10: Cell Growth and Division 2009
Eukaryotic Chromosomes
– In eukaryotic cells, chromosomes are located
in the nucleus, and are made up of
chromatin.
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Chap 10: Cell Growth and Division 2009
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Chromatin is composed of DNA and
histone proteins.
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DNA coils around histone proteins to
form nucleosomes.
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• The nucleosomes interact with one
another to form coils and supercoils that
make up chromosomes.
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Biology notes-Chapter 8
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Chromosomes structure cont:
• Chromosomes contain 2 identical halves each half of
the chromosome is called a chromatid
• Chromatids form when the DNA makes a copy of
itself before cell division
• When the cell divides each ½ gets a copy
• Chromatids are attached by the centromere
• When DNA is not tightly packed it is call chromatin
• Prokaryotes DNA is simple, circular, one
chromosome, very compact to fit in the cell
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Biology notes-Chapter 8
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Chromosomes Numbers
•
Each species has a set number of
chromosomes
Must know terms:
1. Sex chromosomes: are chromosomes that
determine the sex of an organism, they may
also carry genes for other characteristics (X,
Y) (2 humans)
2. Autosomes- all non sex chromosomes
(44 of humans )
Biology notes-Chapter 8
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Chromosomes Numbers cont:
3. Homologous chromosomes- they are
chromosomes that are the same sex and
shape and carry genes from the same traits
4. Karyotype- photomicrograph of
chromosomes in a normal dividing cell found
in human cells (46 chromosomes)
22 homologous pairs of autosomes
2 sex chromosomes
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Karyotype
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Diploid (2n) and haploid (n)
• If a cell is said to have 2 sets of chromosomes it is
said it is diploid
• They have two sex chromosomes in animals including
animals
• Except for reproductive cells like sperm and eggs or
generally called gametes
Ex the 2n or diploid or number of chromosomes is 46
and 22 pairs
If it is haploid it contains only one set of chromosomes
for example only has one set of the autosomes and
sex chromosomes 23 total
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Biology notes-Chapter 8
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The Cell Cycle
What are the main events of the cell cycle?
– During the cell cycle, a cell grows, prepares
for division, and divides to form two daughter
cells.
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Chap 10: Cell Growth and Division 2009
The Prokaryotic Cell Cycle
– The prokaryotic cell cycle is a regular pattern of
growth, DNA replication, and cell division.
– Most prokaryotic cells begin to replicate, or copy,
their DNA once they have grown to a certain size.
– When DNA replication is complete, the cells
divide through a process known as binary fission.
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Chap 10: Cell Growth and Division 2009
Cell division in prokaryotes
• Have no true nuclei or membrane-bound
organelles
• DNA is not coiled around proteins- it is circular
attached to the inner surface of the plasma
membrane like a rope attached to the inner
wall of a tent
• Process of cell division is Binary fission
Biology notes-Chapter 8
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Binary fission
Is the division of a prok into
two offspring cells
1. DNA is copied  get two
identical chromosomes
2. A new cell membrane then
begins to develop between
the two DNA copies
3. Cell grows till its 2x the
original size
4. Cells split containing
identical chromosomes
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Binary fission
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The Eukaryotic Cell Cycle
– The eukaryotic cell cycle
consists of four phases:
G1, S, G2, and M.
– Interphase is the time
between cell divisions. It
is a period of growth that
consists of the G1, S, and
G2 phases. The M phase
is the period of cell
division.
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Chap 10: Cell Growth and Division 2009
G1 Phase: Cell Growth
– In the G1 phase, cells
increase in size and
synthesize new
proteins and
organelles.
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Chap 10: Cell Growth and Division 2009
S Phase: DNA Replication
– In the S (or
synthesis) phase,
new DNA is
synthesized when the
chromosomes are
replicated.
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G2 Phase: Preparing for Cell
Division
– In the G2 phase,
many of the
organelles and
molecules required
for cell division are
produced.
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Chap 10: Cell Growth and Division 2009
M Phase: Cell Division
– In eukaryotes, cell
division occurs in two
stages: mitosis and
cytokinesis.
– Mitosis is the division
of the cell nucleus.
– Cytokinesis is the
division of the
cytoplasm.
– Or a G0: stage in which
the cell is mature and no
longer dividing
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Biology notes-Chapter 8
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• Division of the nucleus
• Occurs during cell division
• Continuous process that allows for the organized
distribution of cell’s copied DNA to offspring cells
• Divided into four phases PMAT
1. prophase
2. metaphase
3. Anaphase
4. telophase
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Chap 10: Cell Growth and Division 2009
Important Cell Structures
Involved in Mitosis
– Chromatid – each strand of a duplicated
chromosome
– Centromere – the area where each pair of
chromatids is joined
– Centrioles – tiny structures located in the cytoplasm
of animal cells that help organize the spindle
– Spindle – a fanlike microtubule structure that helps
separate the chromatids
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Chap 10: Cell Growth and Division 2009
Prophase
– During prophase,
the first phase of
mitosis, the
duplicated
chromosome
condenses and
becomes visible.
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Chap 10: Cell Growth and Division 2009
Prophase
– During prophase,
the first phase of
mitosis, the
duplicated
chromosome
condenses and
becomes visible.
– The centrioles
move to opposite
sides of nucleus and
help organize the
spindle.
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Chap 10: Cell Growth and Division 2009
Prophase
–
During prophase, the
first phase of mitosis, the
duplicated chromosome
condenses and becomes
visible.
–
The centrioles move to
opposite sides of nucleus
and help organize the
spindle.
–
The spindle forms and
DNA strands attach at a
point called their
centromere.
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Chap 10: Cell Growth and Division 2009
Prophase
–
During prophase, the first
phase of mitosis, the duplicated
chromosome condenses and
becomes visible.
–
The centrioles move to
opposite sides of nucleus and
help organize the spindle.
–
The spindle forms and DNA
strands attach at a point called
their centromere.
–
The nucleolus disappears and
nuclear envelope breaks down.
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Chap 10: Cell Growth and Division 2009
Metaphase
– During metaphase,
the second phase of
mitosis, the
centromeres of the
duplicated
chromosomes line up
across the center of
the cell.
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Chap 10: Cell Growth and Division 2009
Metaphase
– During metaphase, the
second phase of mitosis,
the centromeres of the
duplicated chromosomes
line up across the center
of the cell.
– The spindle fibers
connect the centromere
of each chromosome to
the two poles of the
spindle.
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Chap 10: Cell Growth and Division 2009
Anaphase
– During anaphase,
the third phase of
mitosis, the
centromeres are
pulled apart and the
chromatids separate
to become individual
chromosomes.
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Chap 10: Cell Growth and Division 2009
Anaphase
– During anaphase, the
third phase of mitosis,
the centromeres are
pulled apart and the
chromatids separate to
become individual
chromosomes.
– The chromosomes
separate into two
groups near the poles of
the spindle.
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Chap 10: Cell Growth and Division 2009
Telophase
– During telophase,
the fourth and final
phase of mitosis, the
chromosomes spread
out into a tangle of
chromatin.
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Chap 10: Cell Growth and Division 2009
Telophase
– During telophase,
the fourth and final
phase of mitosis, the
chromosomes spread
out into a tangle of
chromatin.
– A nuclear envelope
re-forms around each
cluster of
chromosomes.
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Chap 10: Cell Growth and Division 2009
Telophase
– During telophase, the
fourth and final phase of
mitosis, the chromosomes
spread out into a tangle of
chromatin.
– A nuclear envelope reforms around each cluster
of chromosomes.
– The spindle breaks apart,
and a nucleolus becomes
visible in each daughter
nucleus.
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Chap 10: Cell Growth and Division 2009
Cytokinesis
How do daughter cells split apart after mitosis?
– Cytokinesis completes the process of cell
division – it splits one cell into two.
– Cytokinesis is the division of the cytoplasm.
– The process of cytokinesis is different in
animal and plant cells.
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Chap 10: Cell Growth and Division 2009
Cytokinesis in Animal Cells
– The cell membrane is drawn in until the
cytoplasm is pinched into two equal parts.,
Cleavage furrow
– Each part contains its own nucleus and
organelles.
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Chap 10: Cell Growth and Division 2009
Cytokinesis in Plant Cells
– In plants, the cell membrane is not flexible
enough to draw inward because of the rigid
cell wall.
– Instead, a cell plate forms between the
divided nuclei that develops into cell
membranes.
– A cell wall then forms in between the two
new membranes.
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Chap 10: Cell Growth and Division 2009
Biology notes-Chapter 8
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The Stages of the Cell Cycle
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