Download Lecture 5.9

5.9 IN
What happens to a cell when it gets
too big?
The cell will divide in two. Mature plant
cells and some animal cells (nerve and
muscle) never divide.
The Cell
Cell Division
The Cell’s Life Is a Cycle
Section 5.9
I.  Why are cells so small?
Cell Size
Cell Size Limitation
Eukaryotes: 5-20 µm; nerve cells to 1 m length
The cell that ate
New York!
Prokaryotes: 1-10 µm
A. Diffusion
Substances slowly travel through the cell, so
large cells would be less efficient than small
cells.
B. Surface area to volume ratio limits cell
size:
Limits on Cell Size
The cell’s surface provides interaction with
their environment.
Double the cell size (from 1 mm to 2 mm):
•  Surface area increases 4 times.
•  Volume increases 8 times.
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As cell size increases, the cell volume
increases much faster than the surface area!
There is not enough cell membrane (surface
area) to support the diffusion of nutrients,
gasses, and waste (volume inside) fast
enough!
C. Large cells have less surface area per
volume. Therefore, it is more efficient to be small
(materials enter and leave the cell more rapidly).
•  Cells would die due to lack of nutrients or toxic
buildup
•  Cells divide before they get too big!
II. Cellular Reproduction
Cell division - process by which one cell
divides into 2 cells (daughter cells),
each containing a copy of DNA. Also
known as growth and reproduction.
1. Mitosis - division of body cells
(somatic cells); skin, nerves, etc.
2. Meiosis - division of sex cells
(gametes); egg and sperm
Sketch the Cell Cycle in your notebook.
III. Cell Cycle
Eukaryotic cell life from formation to cell division;
Two stages (Interphase, Mitotic phase)
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Interphase
•  Cell spends most of its life in interphase.
•  Normal metabolism takes place (cellular
respiration, protein synthesis)
G1 Phase
•  Rapid growth and metabolism
•  Proteins and RNA synthesized
•  Preparation for mitosis; G1 → S → G2
S Phase
•  DNA content doubles and is copied exactly
G2 Phase
•  More growth and metabolism
•  Organelles duplicate
Mitosis
Cytokinesis
•  Nuclear division (nucleus
reproduces)
•  Cytoplasm (with its organelles) divides into two
daughter cells
•  Chromosomes (DNA wrapped
around proteins) are visible
•  animal cell - cell pinches inward (cleavage
furrow)
Chromosome
Interphase
Cytokinesis
Cy
s
ne
ki
to
is
ito
si
s
•  plant cell - new cell wall forms between 2 cells
G1
Rapid growth, metabolism
Proteins, RNA made
S phase
DNA synthesis
and replication
G2
Cell prepares for division
Organelles made
M
•  Cytoplasm (with its organelles) divides into two
daughter cells
M
(M) ITOTIC
PH
AS
E
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5.9 OUT
Which is the longest stage and includes
the doubling of DNA?
a) G1 phase
Read Chapter 5.9
Quiz 5.6-6.11 1/20/17
b) Mitosis
c) Cytokinesis
d) Interphase
Concept Map
Create a concept map using the following
terms. Connect the terms with an arrow and a
verb! A term may be used more than once.
cell size
cell membrane
mitosis
interphase
DNA
cytokinesis
nutrients
diffusion
cytoplasm
mitotic phase
growth & metabolism
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