1. Cell Growth and Reproduction
• CELL SIZE LIMITATION (8.2)
•T H E C E L L C Y C L E ( 8 . 2 )
• CONTROL OF THE CELL CYCLE (8.3)

2. Answer these questions:
• WHY CAN’T ORGANISMS BE JUST ONE GIANT CELL?
• IF A CELL WANTS TO MAKE A COPY OF ITSELF, WHAT DO
YOU THINK IS THE FIRST STEP?
• WHAT ORGANELLES ARE INVOLVED IN CELLULAR
REPRODUCTION?

3. Cell Size Limitation
 Cell size is limited by…
 Diffusion rate
 DNA
 Surface area-to-volume ratio
 Diffusion Rate
 Fast and efficient over short distances
 Becomes slow and inefficient as distances become larger

4. Cell Size Limitation
 DNA
 To build proteins, the blueprints for those proteins (DNA)
must be copied
 The cell cannot survive unless there is enough DNA to support
the protein needs of the cell
 Answer these questions:
 What does DNA code for?
 Where is DNA stored?
 How can we increase cell size and still have enough DNA to
support the protein needs of the cell?

6. Cell Size Limitation
 Surface area-to-volume ratio
 As size increases, volume increases much faster than surface
area
 Answer this question:
 How does the surface area-to-volume ratio affect cell function?

7. Cell Size Limitation
 Surface area-to-volume ratio
 The demand for oxygen, nutrients and waste removal grows
faster than the surface area of the plasma membrane allows

8. Answer these questions:
• WHAT 3 FACTORS LIMIT CELL SIZE?
• WHY DO WE (AND OTHER ORGANISMS) MAKE NEW
CELLS?
• WHAT ARE CHROMOSOMES?

9. Cell Reproduction
 Cell division results in
two cells that are
identical to the
original, parent cell
 Cells are constantly
growing, dividing and
dying
 New cells are used for
growth, repair/replacem
ent

10. Cell Reproduction
 In the nucleus of each cell, the DNA molecule is
packaged into thread-like structures called
chromosomes.
 Chromosomes are not visible in the cell’s nucleus—
not even under a microscope—when the cell is not
dividing.
 However, the DNA that makes up chromosomes
becomes more tightly packed during cell division and
is then visible under a microscope.

11. Cell Reproduction
 For most of a cell’s
lifetime, chromosomes
exist as chromatin
 Chromatin is long
strands of DNA
wrapped around
proteins called
histones

12. Cell Reproduction
 Before a cell can divide, it must pack up and
untangle the chromatin so it can be moved easily
 We see chromosomes when the chromatin is tightly
packed

13. https://www.youtube.com/watch?v=gbSIBhFwQ4s

14. The Cell Cycle
 The cell cycle is the
sequence of growth and
division of a cell
 The growth period is
called interphase
 The division period is
called mitosis

15. The Cell Cycle - Interphase
 Divided into 3 parts



G1 – cell growth, high
protein production
S – DNA synthesis
G2 – Organelles and other
cell parts for cell division
are assembled

16. The Cell Cycle - Mitosis
 The 4 phases of mitosis




Prophase
Metaphase
Anaphase
Telophase

17. The Cell Cycle – Mitosis: Prophase
Prophase
 The long stringy chromatin coils up into visible
chromosomes
 Each duplicated chromosome is made up of two
halves called sister chromatidsheld together by a
centromere

19. The Cell Cycle – Mitosis: Prophase
 As prophase
continues, the nuclear
membrane and nucleolus
disintegrate
 In animals, two pairs of
centrioles begin to
migrate to opposite ends
of the cell
 The spindle (made of
microtubules) begins to
form

21. The Cell Cycle – Mitosis: Metaphase
Metaphase
 The chromosomes line up across the middle of the
cell
 Each sister chromatidis attached to its own
spindle fiber at the centromere.
 The other end of the spindle fiber attaches to the
centriole (in animals) or the cell wall (in plants)

23. The Cell Cycle – Mitosis: Anaphase
Anaphase
 Anaphase is marked by the separation of sister
chromatids
 Centromeres split apart and each chromatid of a
pair is pulled to opposite ends of the cell

25. The Cell Cycle – Mitosis: Telophase
Telophase
 Chromatids reach the opposite poles of the cell
 Chromosomes unwind
 The spindle breaks down
 The nucleolus reappears
 A new nuclear membrane forms around each set
of chromosomes
 A new plasma membrane begins to form between
the two new nuclei

27. Cytokinesis
 Following telophase, the cells cytoplasm divides in a
process called cytokinesis
 In animal cells, the plasma membrane folds in at the
equator
 In plant cells, a cell plate is constructed between the
two new cells, allowing new cell membranes and cell
walls to form

29. Results of Mitosis
 Mitosis results in 2 new cells with identical
chromosome sets
 The two daughter cells will carry out the same
cellular processes and functions as those of the
parent cell
 Each daughter cell will grow and divide

30. Videos
 Computer animated mitosis:
https://www.youtube.com/watch?v=VGV3fv-uZYI
 Black and White:
https://www.youtube.com/watch?v=ZeW8HaCUtOQ
 Colored:
https://www.youtube.com/watch?v=P7m3WfzgZdI
 Hank Green: https://www.youtube.com/watch?v=L0k-
enzoeOM

31. Control of the Cell Cycle

32. Control of the Cell Cycle
 At each checkpoint, if
conditions are
met, cyclin tells cyclindependant kinase to
move to the next step of
the cell cycle

34. Control of the Cell Cycle
 DNA holds the code for the construction of
cyclin, cyclin-dependant kinaseand all of the
other proteins and enzymes involved in control of
the cell cycle
 If the genes that code for any of these are
mutated, dysregulation of the cell cycle occurs



Checkpoints may not work
The signal for cell division may be given when more cells are
not needed
This is cancer