Getting Through

1
Section 10-1

• Getting Through
• Materials move through cells by diffusion.
  Oxygen and food move into cells, while waste
  products move out of cells. How does the size of
  a cell affect how efficiently materials get to
  all parts of a cell?
• Work with a partner to complete this activity.

1. On a sheet of paper, make a drawing of a cell
that has the following dimensions 5 cm x 5 cm x
5 cm. Your partner should draw another cell about
one half the size of your cell on a separate
sheet of paper. 2. Compare your drawings. How
much longer do you think it would taketo get
from the cell membrane to the center of the big
cell than from the cell membrane to the
center of the smaller cell? 3. What is the
advantage of cells being small?
2
Section Outline
Section 10-1

• 101 Cell Growth
• A. Limits to Cell Growth
• 1. DNA Overload
• 2. Exchanging Materials
• 3. Ratio of Surface Area to Volume
• 4. Cell Division

3
Section 10-1

• There are 2 main reasons why cells divide rather
  than growing larger
• DNA Overload-when a cell is small, the
  information stored in that DNA meets the needs of
  the cell as a cell grows it usually does not
  make extra copies of DNA which created an
  information shortage.
• ex. Small town library

4
Section 10-1

• Material Exchange-all food, water, oxygen and
  wastes must pass through the cell membrane. The
  rate at which this exchange takes place depends
  on the surface area of the cell.
• Ratio of Surface Area to Volume-
• Volume increases much more rapidly than the
  surface area, causing the ratio of surface area
  to volume to decrease.
• ex. Main street

5
Ratio of Surface Area to Volume in Cells
Section 10-1
Cell Size
Surface Area (length x width x 6)
Volume (length x width x height)
Ratio of Surface Area to Volume
6
Section 10-1

• Division of the Cell
• The process by which a cell divides into 2 new
  daughter cells.
• Before the cell divides, DNA replication takes
  place.
• These processes allow the cells to
• a. Reduce volume
• b. Increase surface area to volume ratio
• c. Maintain available genetic information

7
Section 10-2

• Cell Cycle
• The cell cycle represents recurring events that
  take place in the period of time from the
  beginning of one cell division to the beginning
  of the next. In addition to cell division, the
  cell cycle includes periods when the cell is
  growing and actively producing materials it needs
  for the next division.

1. Why is the cell cycle called a cycle? 2. Why
do you think that it is important for a cell to
grow in size during its cell cycle? 3. What
might happen to a cell if all events leading up
to cell division took place as they should, but
the cell did not divide?
8
Section Outline
Section 10-2

• 102 Cell Division
• A. Chromosomes
• B. The Cell Cycle
• C. Events of the Cell Cycle
• D. Mitosis
• 1. Prophase
• 2. Metaphase
• 3. Anaphase
• 4. Telophase
• E. Cytokinesis

9
Video 1
10
Section 10-2

• Chromosomes-are comprised of DNA and protein.
  These carry the genetic information in eukaryotic
  cells. Only visible during cell division.
• Before cell division, each chromosome is
  replicated, creating identical sister
  chromatids. During cell division each chromatid
  will go to the 2 new cells.

11
Section 10-2

• Cell Cycle-
• 1. Cell grows
• 2. Prepares for division
• 3. Divides to form 2 daughter cells
• 4. Daughter cells begin cycle again

12
Figure 104 The Cell Cycle
Section 10-2
G1 phase
M phase
S phase
G2 phase
13
Section 10-2

• Interphase
• This phase consists of
• G1 phase-main growth of a cell
• S phase- DNA replicated
• G2 phase-many organelles and molecules
  required for cell
• division are produced

14
Figure 105 Mitosis and Cytokinesis
Section 10-2
Spindle forming
Centrioles
Centromere
Chromatin
Centriole
Nuclear envelope
Chromosomes (paired chromatids)
Interphase
Prophase
Spindle
Cytokinesis
Centriole
Metaphase
Individual chromosomes
Telophase
Anaphase
Nuclear envelope reforming
15
Section 10-2

• Mitosis
• part of eukaryotic cell division in which the
  nucleus divides
• Lasts a few minutes to several days.
• Four phases
• 1. Prophase
• 2. Metaphase
• 3. Anaphase
• 4. Telophase

16
Section 10-2

• Prophase
• This is the first and longest phase.
• Events that take place include
• 1. chromosomes become visible
• 2. centrioles separate and move to
  opposite sides
• 3. spindle (fan-like microtubule
  structure) forms
• 4. chromosomes attach to spindle fibers

17
Figure 105 Mitosis and Cytokinesis
Section 10-2
Spindle forming
Centrioles
Centromere
Chromatin
Centriole
Nuclear envelope
Chromosomes (paired chromatids)
Interphase
Prophase
Spindle
Cytokinesis
Centriole
Metaphase
Individual chromosomes
Telophase
Anaphase
Nuclear envelope reforming
18
Section 10-2

• Metaphase
• Second phase of mitosis
• Events that take place include
• 1. chromosomes line up in the center of
  the cell
• 2. microtubules connect the centromere of
  each chromosome to the two poles of the
  spindle

19
Figure 105 Mitosis and Cytokinesis
Section 10-2
Spindle forming
Centrioles
Centromere
Chromatin
Centriole
Nuclear envelope
Chromosomes (paired chromatids)
Interphase
Prophase
Spindle
Cytokinesis
Centriole
Metaphase
Individual chromosomes
Telophase
Anaphase
Nuclear envelope reforming
20
Section 10-2

• Anaphase
• Third phase of mitosis
• Events that take place include
• 1. the centromeres that join the sister
  chromatids split allowing the sister
  chromatids to become individual
  chromosomes
• 2. chromosomes move towards the ends of
  the cell

21
Figure 105 Mitosis and Cytokinesis
Section 10-2
Spindle forming
Centrioles
Centromere
Chromatin
Centriole
Nuclear envelope
Chromosomes (paired chromatids)
Interphase
Prophase
Spindle
Cytokinesis
Centriole
Metaphase
Individual chromosomes
Telophase
Anaphase
Nuclear envelope reforming
22
Section 10-2

• Telophase
• Fourth and final phase of mitosis
• Events that take place include
• 1. chromosomes are at opposite ends of
  cell and lose shape
• 2. two new nuclear envelopes will form
  around the chromosomes

23
Figure 105 Mitosis and Cytokinesis
Section 10-2
Spindle forming
Centrioles
Centromere
Chromatin
Centriole
Nuclear envelope
Chromosomes (paired chromatids)
Interphase
Prophase
Spindle
Cytokinesis
Centriole
Metaphase
Individual chromosomes
Telophase
Anaphase
Nuclear envelope reforming
24
Section 10-2

• Cytokinesis
• Animal cells-cell membrane is drawn inward
  until the cytoplasm is pinched into 2 equal
  parts
• Plant cells-a cell plate forms midway between
  the divided nuclei. This eventually becomes a
  cell membrane and a cell wall.

25
Figure 105 Mitosis and Cytokinesis
Section 10-2
Spindle forming
Centrioles
Centromere
Chromatin
Centriole
Nuclear envelope
Chromosomes (paired chromatids)
Interphase
Prophase
Spindle
Cytokinesis
Centriole
Metaphase
Individual chromosomes
Telophase
Anaphase
Nuclear envelope reforming
26
Concept Map
Section 10-2
Cell Cycle
includes
is divided into
is divided into
27
Interest Grabber
Section 10-3

• Knowing When to Stop
• Suppose you had a paper cut on your finger.
  Although the cut may have bled and stung a
  little, after a few days, it will have
  disappeared, and your finger would be as good as
  new.

1. How do you think the body repairs an injury,
such as a cut on a finger? 2. How long do you
think this repair process continues? 3. What do
you think causes the cells to stop the repair
process?
28
Section Outline
Section 10-3

• 103 Regulating the Cell Cycle
• A. Controls on Cell Division
• B. Cell Cycle Regulators
• 1. Internal Regulators
• 2. External Regulators
• C. Uncontrolled Cell Growth

29

• Different types of cells go through the cell
  cycle at different rates.
• Contact Inhibition
• - in normal tissues cells stop dividing when
  
• they come into contact with other cells
• - when contact is lost they begin dividing again
• - ex. cut in your skin

30
Control of Cell Division
Section 10-3
31

• Cyclins are chemicals that cells produce which
  regulate the timing of the cell cycle in
  eukaryotic cells.

The sample is injected into a second cell in G2
of interphase.
A sample of cytoplasm is removed from a cell in
mitosis.
As a result, the second cell enters mitosis.
32

• Internal regulators proteins that respond to
  events inside the cell and allow the cell cycle
  to proceed or not.
• - produced only when all DNA is replicated
• - controls until all chromosomes attached to
  spindle fibers
• External regulators proteins that respond to
  events outside the cell.
• - growth factors and surface receptors

33

• Uncontrolled Cell Growth Cancer
• - cancer cells do not respond to normal controls
• - divide uncontrollably and form masses of cells
  called tumors
• - cells may metastasize break loose from
  tumor and spread
• - mutations in a gene called p53 are often
  what triggers cancer

34

• Stem Cells unspecialized cells which can give
  rise to other cell types.
• - in an embryo there are many stem cells which
  will give rise to the specialized cells of your
  body
• - adult stem cells are present, but harder to
  find
• - medical research is trying to use stem cells to
  cure disease.

35
Figure 108 Effect of Cyclins
Section 10-3
36
Video 2
Video 2
Animal Cell Cytokinesis
Click the image to play the video segment.
37
Section 1 Answers
Interest Grabber Answers
1. On a sheet of paper, make a drawing of a cell
that has the following dimensions 5 cm x 5 cm x
5 cm. Your partner should draw another cell about
one half the size of your cell on a separate
sheet of paper. 2. Compare your drawings. How
much longer do you think it would taketo get
from the cell membrane to the center of the big
cell than from the cell membrane to the
center of the smaller cell? It would take twice
the amount of time. 3. What is the advantage of
cells being small? If cells are small, materials
can be distributed to all parts of the cell
quickly.
38
Section 2 Answers
Interest Grabber Answers
1. Why is the cell cycle called a cycle? It
represents recurring events. 2. Why do you think
that it is important for a cell to grow in size
during its cell cycle? If a cell did not grow in
size, each cell division would produce
progressively smaller cells. 3. What might
happen to a cell if all events leading up to cell
division took place as they should, but the cell
did not divide? Students may infer that a cell
that undergoes all sequences of the cell cycle
would grow increasingly largerto a point at
which the cell could no longer exchange materials
with the environment efficiently enough to live.
39
Section 3 Answers
Interest Grabber Answers
1. How do you think the body repairs an injury,
such as a cut on a finger? The cut is repaired
by the production of new cells through cell
division. 2. How long do you think this repair
process continues? Cell division continues until
the cut is repaired. 3. What do you think causes
the cells to stop the repair process? Students
will likely say that when the cut is filled in,
there is no room for more cells to grow.
40
End of Custom Shows

• This slide is intentionally blank.