cell division and growth chapter 10 how large can a cell be? is there a limit? dna “overload” =...
TRANSCRIPT
Cell Division and Growth
Chapter 10
How large can a cell be? Is there a limit?
• DNA “overload” = when a cell becomes too large and an “information crisis” occurs
• Too difficult to exchange materials
• The speed of exchange is determined by the cell membrane
What determines the rate of exchange of materials?
• Surface area to volume ratio
• The larger the surface area-to-volume ratio the more materials a cell can exchange with its environment
Example problems• A cube with all
sides 1 cm in length
• A cube with all sides 2 cm in length
What happens when a cell becomes too big?
1. The cell can die.
2. The cell can divide to produce two new daughter cells (cell division)
Mitosis• Process in which a cell with a nucleus
divides and forms two identical nuclei.
• Refers to division of nucleus
• Cytokinesis = division of the cytoplasm
• Asexual Reproduction• One parent
• Offspring identical to parent cell
Nucleus review:• Control center• Location of genetic material• Chromatin = material of which
chromosomes are composed• Histones = small groups of proteins where
chromatin is found• Chromosome = short, thick, rod-like,
chromatin structures
Chromosome structure
• Chromatid = each individual strand of a chromosome
• Centromere = region where chromatids join.
•Mitosis is a continuous process which can be divided into phases.
Interphase
• Not considered a “phase” of mitosis.
• Time when a cell is between mitotic cycles
• Often called the “resting stage”
• This is NOT an accurate description
Events of Interphase:
• Cell is growing in size• Proteins,organelles, and nucleic acids
are produced• Majority of a cell’s “life” • Prepares for mitosis
• Chromosomes and centrioles replicate.
Relative lifetime of a cell:902.52.52.52.5
Interphase
Prophase
Metaphase
Anaphase
Telophase
1) Prophase
• The double chromosomes are visible as threads that coil and contract into thick rods
Events of prophase
• Centrioles migrate toward opposite ends (poles) of the cell.
• Microtubules extend from centrioles to form asters and eventually a spindle.
• Toward end of prophase chromosomes begin to move to center (equator) of the cell
• Nuclear envelope and nucleolus disappears
Late Prophase:
2) Metaphase
• Centromeres line up on equator
• Two chromatids of each chromosome become separate chromosomes
ANIMAL
PLANT
3) anaphase
• The duplicated chromosomes move to opposite poles
• Microtubules help to move the chromosomes.
ANIMAL
PLANT
4) Telophase
• Chromosomes uncoil and get longer
• Spindle fibers disappear
• Nuclear membrane forms around “daughter” nuclei.
ANIMAL
PLANT
Review of mitosis
• Mitosis Movie and tutorial
Cytokinesis• Division of the cytoplasm.
• Begins during late anaphase and finishes during telophase in animal cells.
Controlling cell division
• Do all cells divide at the same speed?
• Why do cells divide at different speeds?
• When do cells divide fastest during one’s life?
Regulating division
• Cyclins : proteins found in eukaryotic cells that regulate the timing of the cell cycle.
• Internal regulators: proteins that work inside the cell
• External regulators: proteins that respond to events outside the cell• growth factors, after injury, embryological
• Defined as uncontrolled cell division.
• If cells continue to divide over and over, eventually a mass of cells can be formed called a tumor that may interfere with normal tissuue or cellular functions.
Assignment
• Pages 257-259
Page 257-258 1-10,14,19,20,27,29
Page 259 1-12