1. What limits cell growth? & The Cell Cycle: Mitosis Section 8.2
The life of cells
What limits cell growth?
&
The Cell Cycle: Mitosis
Section 8.2

2. What limits cell size? Diffusion DNA Surface area-to-volume ratio
Slow & inefficient over long distances
DNA
Copying DNA takes time
Must be enough DNA to support cell’s protein needs
Surface area-to-volume ratio
Volume increases much faster than surface area
If cell were too big, it couldn’t process nutrients and wastes properly – would starve or be poisoned

3. Cell Reproduction Cells can’t grow forever
Stop growing or divide
Reproduction (division) is necessary for life to continue

4. Reproduction in prokaryotes
Very simple
Binary fission
cell pinches in two
Each has its
own DNA

5. Reproduction in Eukaryotes
Much more complicated
DNA in membrane-bound nucleus
Chromosomes – contain DNA material
Come in pairs (sister chromatids), joined by a centromere
Chromatin – long strands of DNA
Most of the time, chromosomes exist as chromatin
See page 205

6. http://micro. magnet. fsu

7. Chromosome Terms
Diploid (2n) – cell contains pairs of homologous chromosomes
Body cells AKA somatic cells
Haploid (n) – cell has only one chromatid from each pair
Sex cells AKA gametes AKA egg & sperm

8. Karyotype of a human somatic cell

9. Cell Cycle Sequence of growth and division Interphase Mitosis Prophase
Metaphase
Anaphase
Telophase
Cytokinesis

10. Interphase Majority of cell’s life Very busy time Cell grows in size
Carries on metabolism
DNA synthesis
& replication
student.ccbcmd.edu/.../DNArep/pcinterphase.html

13. Activity
Look at problem-solving lab on page 204

14. Mitosis Nuclear division
Result: two daughter cells, each with a set of chromosomes
4 stages
Prophase
Metaphase
Anaphase
Telophase

15. Prophase stringy chromatin coils up  chromosomes
Nucleus begins to disappear
Nuclear envelope & nucleolus disintegrate
*In animal cells* - centrioles migrate to opposite ends of cell
Spindle – forms between centrioles
(in plant cells, spindle forms without the centrioles)

18. Metaphase (M is for middle)
Chromosomes attached to spindle fibers by centromeres
Line up on midline
or equator

20. Anaphase Centromeres split Sister chromatids separate
Pulled apart by shortening of spindle fibers

22. Telophase (think telephone – requires two people to talk)
Chromatids reach opposite poles of cell
Prophase changes are reversed
Chromosomes unwind
Spindle breaks down
Nucleolus reappears
New nuclear envelope forms around each set of chromosomes

25. Cytokinesis Cytoplasm divides
Animals – plasma membrane pinches in at equator
Plants – cell plate is laid down across equator
New cell walls form

26. Results of mitosis **Cellular heirarchy** Cells  tissues  organs 
Guarantees genetic continuity
Two new cells with identical sets of chromosomes
Unicellular organisms – more identical organisms are produced
Multicellular organisms – groups of cells
**Cellular heirarchy**
Cells  tissues  organs 
organ systems  organism

27. Quiz: Cell cycle

28. Division in prokaryotes is called?
A. Binary fission
B. Metaphase
C. Replication
D. Binary fusion

29. 2. Pairs of chromosomes are homologous which means

30. 3. How is cytokinesis different in animal and plant cells?

31. 4. Somatic cells are
A. 4n
B. 2n
C. n
D. 3n

32. 5. Humans have how many pairs of chromosomes?
B. 46
C. 4
D. 2

33. 6. What are the organelles that produce spindle fibers called?
A. Microtubules
B. Centrioles
C. Nucleoli
D. Cytoplasm

34. 7. ____ is the specific region where chromatids are held.
A. Centrioles
B. Telomeres
C. Centromeres
D. Spindle fibers

35. 8. Name the missing phase.
Interphase, Prophase, _________, Anaphase, Telophase

36. 9. Cells spend most of their time in which phase mitosis?
A. Telophase
B. Anaphase
C. Metaphase
D. Prophase
E. Interphase

37. 10. The phase at which the chromosomes are pulled to the poles of the cells.
A. Prophase
B. Anaphase
C. Interphase
D. Metaphase
E. Telophase