Transcript Document

Multicellular Life
Multicellular Life
Cell Cycle
Cell Division
I.
Unicellular Life
A. A single cell makes up the entire organism
1. All prokaryotes (Archaebacteria & Eubacteria)
2. Some Eukaryotes (Protsits & Yeasts)
II. Multicellular Life
A. Organisms composed of two or more cells
(up to trillions of cells)
II. Multicellular Life
B. Levels of Organization
1.
2.
3.
4.
5.
Individual Cell
Tissue
Organ
Organ System
Organism
II. Multicellular Life
CELL-smallest unit of life
TISSUE- group of specialized cells
ORGAN- group of tissues with specific function
ORGAN SYSTEM- multiple organs doing the
same function
ORGANISM- many
organ systems
make up a single
living thing
II. Multicellular Life
C. Cell Specialization
1. Cells become efficient in one process and are
dependent on other cells for the necessities of
life.
a) Only found in Multicellular organisms
b) Cells have a specific role or function that benefits
the whole organism
2. All cells in the same organism will have the
exact same DNA
3. Different cells use different sections of the DNA
called genes.
II. Multicellular Life
C. Cell Specialization
4. Examples:
a) Blood cells carry oxygen
b) Muscle cells contract
c) Nerve cells used for response and signals
II. Multicellular Life
D. Limits to Cell Growth
1. Cells must divide when they become too large.
2. Large cell problems:
a) DNA Overload
Do
cells
get
larger
and
larger?
• DNA unable to meet the needs of a growing cell
• Growth without limitsor
would cause information
Docrisis
cells divide to create more cells?
b) Exchanging materials
• Unable to efficiently move materials in (C6H12O6, O2,
etc.) and wastes out (CO2, H2O, etc.) via the cell
membrane
c) Use food and oxygen more quickly
II. Multicellular Life
D. Limits to Cell Growth
3. Ratio of Surface area to Volume
a) Volume increases more rapidly than
Surface area as the cell grows.
b) If ratio becomes to small the cell has
difficulties exchanging materials.
c) Cell volume determines the amount of
waste production.
II. Multicellular Life
D. Limits to Cell Growth
4. Cell division
a) When cells become too large they must
divide forming two “daughter” cells
b) DNA must replicate first in order for each
daughter cell to have a complete copy of
DNA
c) This ensures that cells have a large (high)
surface area to volume ratio (SA:V)
II. Multicellular Life
D. Limits to Cell Growth
3. Ratio of Surface area to Volume
Cell Size
Surface Area (length x
width x 6)
Volume
(length x width x height)
Ratio of Surface Area to
Volume
III. Cell Cycle
Cell Cycle
includes
Interphase
Grows &
replicates
DNA
M phase
(Mitosis)
is divided into
G1 phase
S phase
DNA
replication
Cell
Division
is divided into
G2 phase
Prophase
Prepare for
Prepare
mitosis
(organelles &
molecules made)
Metaphase
Anaphase
Telophase
Middle
Away
Two cells
III. Cell Cycle
A. There are two main phases of the cell cycle
1. Interphase
2. M- Phase
III. Cell Cycle
B. Interphase
1. Longest phase of the cell cycle. Cells the
majority of their lives in this phase.
a) G1-What
1st Growth
is the point of the cell
• replicating
Cell increases in
size and
carries
out normal
DNA
in the
S phase?
life activities
b) S- DNA Replication
• DNA is copied
c) G2- 2nd Growth
• Prepares to divide and copies organelles
III. Cell Cycle
C. M-Phase: Cell Division
1. Mitosis- Division of the nucleus after
Interphase.
a)
b)
c)
d)
Prophase
Metaphase
Anaphase
Telophase
2. Cytokinesis- Division of the cytoplasm
III. Cell Cycle
C. M-Phase: Cell Division
1. Mitosisa) Prophase- PREPARE
• Chromatin condenses into chromosomes
• Centrioles separate & spindle begins to form
• Nuclear envelope breaks down
III. Cell Cycle
C. M-Phase: Cell Division
1. Mitosisb) Metaphase- MIDDLE
• Chromosomes line up in the middle
• Chromosomes connect to spindle fibers at
centromere
III. Cell Cycle
C. M-Phase: Cell Division
1. Mitosisc) Anaphase- AWAY
• Spindle fibers pull sister chromatids apart
• Sister chromatids are pulled to opposite
sides of the cell
III. Cell Cycle
C. M-Phase: Cell Division
1. Mitosisd) Telophase- TWO
• Chromosomes gather at opposite ends
• Two new nuclear envelopes form
III. Cell Cycle
C. M-Phase: Cell Division
2. Cytokinesis
Cleavage
a) Cytoplasm pinches
in halfFurrow
b) Each newly formed daughter cell has equal
numbers of chromosomes
c) In plant cells: a cell plate forms to separate
the 2 cells.
III. Cell Cycle
Let's watch the whole process now.
Source: http://highered.mcgraw-hill.com/olc/dl/120073/bio14.swf
III. Cell Cycle
D. G0 Phase
1. Resting phase
a) No division
b) Some cells never leave
this phase
• Nerve cells
c) Some cells never enter
this phase
• Skin cells
IV. Regulating the Cell Cycle
A. Controls
1. When cells come in contact with each other,
they respond by not growing and dividing.
a) If cells are removed or separated from each other,
cells begin dividing to fill empty space
• Cuts, Scrapes
Injury
Normal growth
Stop growth
Cell growth &
division for repair
IV. Regulating the Cell Cycle
A. Controls
2. Cyclins
a) Proteins that regulate the timing of the cell
cycle in eukaryotes & jumpstart cell division
b) Internal Regulators- Proteins that respond to
events inside the cell. (the cell won’t divide
until DNA replicates)
c) External Regulators- Proteins that respond to
events outside the cell. (growth factor
molecules on neighboring cells and
hormones)
How to make a cell start cell division?
A sample
of
cytoplasm
is removed
from a cell
in mitosis.
The sample is
injected into a
second cell in
G2 of
interphase.
As a result,
the second
cell enters
mitosis.
IV. Regulating the Cell Cycle
B. Uncontrolled Cell Growth: Cancer
1. Cells lose ability to control growth
2. Cells stop responding to signals that control
growth
a) Cancer cells may have a defect in the P53
gene (internal regulator). This gene normally
stops the cell cycle until all chromosomes
have been replicated properly. If it is defective
or damaged, cells will accumulate
chromosome damage and stop responding to
cell cycle regulators.
IV. Regulating the Cell Cycle
B. Uncontrolled Cell Growth: Cancer
IV. Regulating the Cell Cycle
B. Uncontrolled Cell Growth: Cancer
3. Treatment
a. Radiation – gamma rays
b. Chemotherapy- Chemicals
c. Removal of Tumor- Surgery
Kills good and
bad Cells