the cell cycle review text – page 201. animal cell plant cell
TRANSCRIPT
The Cell CycleReview
Text – page 201
Animal Cell Plant Cell
Cell Size Limitations
Text - Ch 7 Wide variety of sizes and shapes
RBC (1 um) to nerve cells (1 m) Egg yolk (ostrich) Most are 2-200 um cell scale
Diffusion limits cell size
Selectively permeable membraneI.e. Nutrients in and wastes out
Becomes slow and inefficient as distance between organelles and membrane increases
DNA limits cell size
DNA supports protein needs of cell More than one nucleus
Surface area-to-volume ratio
As cell grows the volume increases faster than the surface area
If cell doubles Nutrients requirements increase 8-fold Waste also increases 8-fold Surface area only increases 4-fold
The cell, therefore, will either starve to death or be poisoned.
Cell Reproduction
Cells divide before they become too large.
Recall: all cells come from pre-existing cells
The Redi Experiment
Pasteur’s swan neck flask experiment
Chromosomes Discovered
Become visible just before cell division Vanish soon after cell division Contain DNA Chromosome (X’me) number varies
Humans 46
Chromosomal Structure
Exist as chromatin most of cell’s life Long strands of DNA Wrapped around proteins called
histones Appear as beads on a string Reorganize before cell division
The Cell Cycle
Def’n: Sequence of growth and division about 3 000 000 cells die in your body
every minute. Cells die due to damage or when they
don’t get enough food or oxygen. Regeneration - Healing of damaged tissue
or the replacement of body parts is called regeneration.
Mitosis
Mitosis is responsible for the cell division that all plants and animals require for:
Growth Repair (and replacement) of body cells
Characteristics of Mitosis
Always only one parent Offspring identical to parents (fast,
convenient, safe)
I.e. asexual reproduction
Phases of the Cell Cycle
IPMAT
Interphase
Most of cell’s life Longest and busiest phase
DNA in thin strands called Chromatin replicate.
Chromatin coils up to form double stranded X’mes.
Interphase
A Centromere connects the original chromatin with its identical replicate.
The cell has a complete extra copy of DNA.
http://www.pitt.edu/~super1/lecture/lec19281/004.htm
Chromosome
Prophase
Prophase Duplicate DNA is easily seen under
microscope. Nucleolus and Nuclear Membrane
disappear. Centrioles move to opposite sides of the
cell. Spindle fibres (like a scaffold) grow out of
each centriole and attach to centromere.
Metaphase
http://www.madsci.org/posts/archives/2000-11/974783537.Cb.1.jpg
Metaphase Spindle fibres pull on centromeres double X’mes pulled into a line across
the middle Shortest phase
Anaphase
Anaphase Spindle fibers contract fully Centromeres are pulled apart 1 copy of DNA goes to each side of the
cell
Telophase
Telophase A complete set of X’mes arrives at each
centriole. Two daughter cells have formed Spindle fibers disappear Nuclei/nucleoli and nuclear membrane
form. X’mes uncoil into thin chromatin.
Telophase (cont’d) Animal cells
Cleavage furrow – cytokinesis (cell membrane pinches off)
Plant cell A cell plate grows across the cell
Parent Cell Daughter Cells
Animations
NOVA Online | Life's Greatest Miracle | How Cells Divide: Mitosis vs. Meiosis (Flash)
mitosis = cell division hybridmedical-mitosis hybridmedical-mitosis youtube DNA repl'n & spindle