Download Chapter 3 ppt D

PowerPoint® Lecture Slides
prepared by
Barbara Heard,
Atlantic Cape Community
College
CHAPTER
3
Cells: The
Living Units:
Part D
© Annie Leibovitz/Contact Press Images
© 2013 Pearson Education, Inc.
Cell Cycle
• Defines changes from formation of cell
until it reproduces
• Includes:
– Interphase
• Cell grows and carries out functions
– Cell division (mitotic phase)
• Divides into two cells
© 2013 Pearson Education, Inc.
Interphase
• Period from cell formation to cell division
• Nuclear material called chromatin
• Three subphases:
– G1 (gap 1)—vigorous growth and metabolism
• Cells that permanently cease dividing said to be in
G0 phase
– S (synthetic)—DNA replication occurs
– G2 (gap 2)—preparation for division
© 2013 Pearson Education, Inc.
Figure 3.31 The cell cycle.
G1 checkpoint
(restriction point)
S
Growth and DNA
synthesis
G1
Growth
M
G2
Growth and final
preparations for
division
G2 checkpoint
© 2013 Pearson Education, Inc.
Figure 3.33 Mitosis is the process of nuclear division in which the chromosomes are distributed to two daughter
nuclei. (1 of 6)
Interphase
Centrosomes (each
has 2 centrioles)
Plasma
membrane
Nucleolus
Chromatin
Nuclear
envelope
© 2013 Pearson Education, Inc.
Cell Division
• Meiosis - cell division producing gametes
• Mitotic cell division - produces clones
– Essential for body growth and tissue repair
– Occurs continuously in some cells
• Skin; intestinal lining
– None in most mature cells of nervous tissue,
skeletal muscle, and cardiac muscle
• Repairs with fibrous tissue
© 2013 Pearson Education, Inc.
Events Of Cell Division
• Mitosis—division of nucleus
– Four stages ensure each cell receives copy of
replicated DNA
•
•
•
•
Prophase
Metaphase
Anaphase
Telophase
– Cytokinesis—division of cytoplasm by
cleavage furrow
© 2013 Pearson Education, Inc.
Figure 3.31 The cell cycle.
G1 checkpoint
(restriction point)
S
Growth and DNA
synthesis
G1
Growth
M
G2
Growth and final
preparations for
division
G2 checkpoint
© 2013 Pearson Education, Inc.
Prophase
• Chromosomes become visible, each with
two chromatids joined at centromere
• Centrosomes separate and migrate
toward opposite poles
• Mitotic spindles and asters form
© 2013 Pearson Education, Inc.
Prophase
• Nuclear envelope fragments
• Kinetochore microtubules attach to
kinetochore of centromeres and draw
them toward equator of cell
• Polar microtubules assist in forcing poles
apart
© 2013 Pearson Education, Inc.
Figure 3.33 Mitosis is the process of nuclear division in which the chromosomes are distributed to two daughter
nuclei. (2 of 6)
Early Prophase
Early mitotic
spindle
Aster
Chromosome
consisting of two
sister chromatids
© 2013 Pearson Education, Inc.
Centromere
Figure 3.33 Mitosis is the process of nuclear division in which the chromosomes are distributed to two daughter
nuclei. (3 of 6)
Late Prophase
© 2013 Pearson Education, Inc.
Spindle pole
Polar microtubule
Fragments
of nuclear
envelope
Kinetochore
Kinetochore
microtubule
Metaphase
• Centromeres of chromosomes aligned at
equator
• Plane midway between poles called
metaphase plate
© 2013 Pearson Education, Inc.
Figure 3.33 Mitosis is the process of nuclear division in which the chromosomes are distributed to two daughter
nuclei. (4 of 6)
Metaphase
Spindle
Metaphase
plate
© 2013 Pearson Education, Inc.
Anaphase
• Shortest phase
• Centromeres of chromosomes split
simultaneously—each chromatid becomes
a chromosome
• Chromosomes (V shaped) pulled toward
poles by motor proteins of kinetochores
• Polar microtubules continue forcing poles
apart
© 2013 Pearson Education, Inc.
Figure 3.33 Mitosis is the process of nuclear division in which the chromosomes are distributed to two daughter
nuclei. (5 of 6)
Anaphase
Daughter
chromosomes
© 2013 Pearson Education, Inc.
Telophase
• Begins when chromosome movement
stops
• Two sets of chromosomes uncoil to form
chromatin
• New nuclear membrane forms around
each chromatin mass
• Nucleoli reappear
• Spindle disappears
© 2013 Pearson Education, Inc.
Cytokinesis
• Begins during late anaphase
• Ring of actin microfilaments contracts to
form cleavage furrow
• Two daughter cells pinched apart, each
containing nucleus identical to original
© 2013 Pearson Education, Inc.
Figure 3.33 Mitosis is the process of nuclear division in which the chromosomes are distributed to two daughter
nuclei. (6 of 6)
Telophase
© 2013 Pearson Education, Inc.
Cytokinesis
Nuclear
envelope
forming
Nucleolus forming
Contractile
ring at
cleavage
furrow
Figure 3.34 Simplified scheme of information flow from the DNA gene to mRNA to protein structure during
transcription and translation.
Nuclear
envelope
Transcription
RNA Processing
DNA
Pre-mRNA
mRNA
Nuclear
pores
Ribosome
Translation
Polypeptide
© 2013 Pearson Education, Inc.
Protein Synthesis
• Occurs in two steps
– Transcription
• DNA information coded in mRNA
– Translation
• mRNA decoded to assemble polypeptides
© 2013 Pearson Education, Inc.
Apoptosis and Modified Rates of Cell
Division
• During development more cells than
needed produced (e.g., in nervous
system)
• Eliminated later by programmed cell death
(apoptosis)
– Mitochondrial membranes leak chemicals that
activate caspases  DNA, cytoskeleton
degradation  cell death
– Dead cell shrinks and is phagocytized
© 2013 Pearson Education, Inc.
Apoptosis and Modified Rates of Cell
Division
• Organs well formed and functional before
birth
• Cell division in adults to replace short-lived
cells and repair wounds
• Hyperplasia increases cell numbers when
needed
• Atrophy (decreased size) results from
loss of stimulation or use
© 2013 Pearson Education, Inc.
Theories of Cell Aging
• Wear and tear theory—Little chemical insults
and free radicals have cumulative effects
• Mitochondrial theory of aging—free radicals in
mitochondria diminish energy production
• Immune system disorders—autoimmune
responses; progressive weakening of immune
response; C-reactive protein of acute
inflammation causes cell aging
© 2013 Pearson Education, Inc.