Blood & circulation
Download
Report
Transcript Blood & circulation
The Cell Cycle
Review
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 membrane
I.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