Download The Cell Cycle Notes from Pearson

TEKS 5A: Describe the stages of the cell cycle, including deoxyribonucleic acid (DNA) replication and mitosis,
and the importance of the cell cycle to the growth of organisms.
What is the cell cycle?
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The cell cycle is a regular series of events
that cells go through as they grow and
divide.
The cell cycle for prokaryotic cells is a
quick succession of growth, DNA
replication, and cell division. Cell division
in prokaryotes is a one-step process called
binary fission (shown right).
Eukaryotic cells have a more complex cell
cycle than prokaryotic cells.
1. Review What is the difference
between a prokaryotic cell and a
eukaryotic cell?
TEKS 5A: Describe the stages of the cell cycle, including deoxyribonucleic acid (DNA) replication and mitosis,
and the importance of the cell cycle to the growth of organisms.
How is the eukaryotic
cell cycle divided?
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The time between cell divisions is called
interphase. The length of interphase
varies depending on cell type.
Eukaryotic interphase is divided into
three steps, or phases: G1, S, and G2.
Eukaryotic cells divide during the M
phase of the cell cycle. The M phase
consists of two steps: mitosis and
cytokinesis.
2. List What are the three steps
of interphase in eukaryotic cells?
TEKS 5A: Describe the stages of the cell cycle, including deoxyribonucleic acid (DNA) replication and mitosis,
and the importance of the cell cycle to the growth of organisms.
What happens during each phase
of eukaryotic interphase?
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G1: Cells do most of their growing during this
phase. It begins when mitosis is complete
and ends when DNA replication begins.
S: DNA is synthesized as chromosomes are
replicated.
G2: Many of the molecules and cell
structures required for cell division are
produced; usually the shortest phase of the
cell cycle.
3. Describe What happens during
the S-phase of interphase?
During interphase, the
cell grows and
replicates its DNA.
TEKS 5A: Describe the stages of the cell cycle, including deoxyribonucleic acid (DNA) replication and mitosis,
and the importance of the cell cycle to the growth of organisms.
What happens during the M phase
of the eukaryotic cell cycle?
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The M phase is usually much shorter
than interphase and results in two
daughter cells.
The first step of the M phase is
mitosis. The cell’s nucleus divides
during mitosis.
The second step of the M phase is
cytokinesis, during which the cell’s
cytoplasm is divided.
4. Describe What happens during
mitosis?
TEKS 5A: Describe the stages of the cell cycle, including deoxyribonucleic acid (DNA) replication and mitosis,
and the importance of the cell cycle to the growth of organisms.
What are the steps
of mitosis?
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Mitosis consists of four steps:
prophase, metaphase, anaphase,
and telophase.
Prophase: nuclear envelope
breaks down, DNA condenses,
spindle begins to form.
Metaphase: replicated
chromosomes, which appear as
paired sister chromatids, line up
across the center of the cell and
attach to spindle.
(contd.)
TEKS 5A: Describe the stages of the cell cycle, including deoxyribonucleic acid (DNA) replication and mitosis,
and the importance of the cell cycle to the growth of organisms.
What are the steps
of mitosis?
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Anaphase: sister chromatids
separate and move toward ends of
the cell.
Telophase: chromosomes
disperse, nuclear envelope
reforms.
5. Review During which phase of
mitosis do sister chromatids line
up along the center of the cell?
TEKS 5A: Describe the stages of the cell cycle, including deoxyribonucleic acid (DNA) replication and mitosis,
and the importance of the cell cycle to the growth of organisms.
What completes the M phase
of the cell cycle?
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Cytokinesis completes the M phase of the
cell cycle. It may begin while telophase is
still taking place.
During cytokinesis, the cytoplasm (which
includes all of the contents of a eukaryotic
cell outside the nucleus) draws inward,
eventually pinching off into two nearly equal
parts. Each part contains a nucleus.
(contd.)
TEKS 5A: Describe the stages of the cell cycle, including deoxyribonucleic acid (DNA) replication and mitosis,
and the importance of the cell cycle to the growth of organisms.
What completes the M phase
of the cell cycle?
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In plant cells and other eukaryotic cells that
have a cell wall, a cell plate forms halfway
between the divided nuclei. It gradually
develops into cell membranes and forms a
complete cell wall surrounding each
daughter cell.
Upon the completion of cytokinesis and the
M phase, a cell enters interphase.
TEKS 5A: Describe the stages of the cell cycle, including deoxyribonucleic acid (DNA) replication and mitosis,
and the importance of the cell cycle to the growth of organisms.
When does DNA replicate?
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Before a cell divides in the M phase, its
DNA is duplicated by a process called
DNA replication.
DNA replication occurs at the beginning of
the S phase of interphase.
It ensures that each daughter cell that
results from cell division will have a
complete set of DNA molecules.
6. Review Why does DNA
replicate before cell division?
DNA replication
TEKS 5A: Describe the stages of the cell cycle, including deoxyribonucleic acid (DNA) replication and mitosis,
and the importance of the cell cycle to the growth of organisms.
How does DNA replicate?
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During replication, proteins
separate the two strands of
the DNA double helix
creating replication forks.
The enzyme DNA
polymerase then produces
two new complementary
strands of DNA, following the
rules of base pairing.
(contd.)
TEKS 5A: Describe the stages of the cell cycle, including deoxyribonucleic acid (DNA) replication and mitosis,
and the importance of the cell cycle to the growth of organisms.
How does DNA replicate?
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Replication “bubbles” move
in both directions along each
chromosome until the entire
DNA molecule has been
replicated.
At the end of the S phase,
each DNA molecule consists
of one “old” strand and one
“new” strand.
TEKS 5A: Describe the stages of the cell cycle, including deoxyribonucleic acid (DNA) replication and mitosis,
and the importance of the cell cycle to the growth of organisms.
What are the rules of base pairing?
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Hydrogen bonds create a nearly perfect fit
between nitrogenous bases along the
center of the DNA molecule.
These bonds form only between certain
base pairs.
Adenine bonds with thymine; guanine
bonds with cytosine.
7. Review What kind of bond
holds the nitrogenous bases
together along the DNA molecule?
TEKS 5A: Describe the stages of the cell cycle, including deoxyribonucleic acid (DNA) replication and mitosis,
and the importance of the cell cycle to the growth of organisms.
How is the cell cycle controlled?
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Movement through the cell cycle is
subject to control by internal and
external regulators.
Internal regulators ensure that a cell
does not move from one phase to
another until certain events have
taken place.
External regulators respond to
events outside the cell and direct
cells to either speed up or slow
down the cell cycle.
8. Infer A set of regulatory proteins
prevents a cell from entering
anaphase until all of its
chromosomes are attached to the
mitotic spindle. Are these
regulatory proteins internal
regulators or external regulators?
TEKS 5A: Describe the stages of the cell cycle, including deoxyribonucleic acid (DNA) replication and mitosis,
and the importance of the cell cycle to the growth of organisms.
What role does the cell cycle have
in the growth of organisms?
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As an organism grows, its cells cannot simply get larger and larger. The
reason is that as cells get bigger, their surface area to volume ratio
decreases.
If a cell gets too big, its surface area is not large enough to get adequate
oxygen and nutrients in and waste out through the cell membrane.
Cells must divide to accommodate the needs of a growing organism.
TEKS 5A: Describe the stages of the cell cycle, including deoxyribonucleic acid (DNA) replication and mitosis,
and the importance of the cell cycle to the growth of organisms.
Why does the rate of the cell cycle
vary among cell types?
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Cells types lost or damaged to wear and tear move quickly through
the cell cycle to provide replacements.
In adults, cells in skin and the digestive tract move through the cell
cycle very quickly; cells in the nervous system divide very rarely.
During embryonic development, cells progress through the cell
cycle very quickly, often dividing as frequently as every hour or two.
(contd.)
TEKS 5A: Describe the stages of the cell cycle, including deoxyribonucleic acid (DNA) replication and mitosis,
and the importance of the cell cycle to the growth of organisms.
Why does the rate of the cell cycle
vary among cell types?
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Upon injury, cells often speed up their
passage through the cell cycle to aid in
healing. The timing of the cell cycle
returns to normal once the injury heals.
9. Infer Which would be more
damaging, an injury to the lining of
the digestive tract or an injury to
the spinal cord? Explain.
When a person breaks a
bone, cells at the edges
of the injury are
stimulated to speed up
the cell cycle so new
cells can heal the break.