1. Cell Growth and Division
Chapter 10 P
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2. Cell Division
About 2 trillion cells- about 25 million cells per second- are produced by an adult human body every day. All cells come from the division of preexisting cells. (cell theory) Cell division or reproduction is the process by which cells produce offspring cells. Cell division differs in prokaryotes and eukaryotes. Cell reproduction in both prok and euk produce the same result – two cells from one!!
Biology notes-Chapter 8

3. Review What are the three parts to the cell theory?
All living organisms are composed of one or more cells.
Cells are the basic units of structure and function in an organism.
Cells come only from the reproduction of existing cells.
Four things common is all cells:
cell membrane, cytoplasm, DNA, ribosomes
Biology notes-Chapter 8

4. How does a cell produce a new cell?
10.1- Why do cells Divide? How do cells Divide? How does a cell control the process of cell division? How does a single undifferentiated cell lead to a complex multicellular organism?
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5. Chap 10: Cell Growth and Division 2009
Voc Terms
Cell Division
Cytokinesis
Asexual reproduction
Prophase
Sexual reproduction
Centromere
Chromosomes
Chromatid
Chromatin
Centriole
Cell cycle
Metaphase
Interphase
Anaphase
Mitosis
telophase
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6. THINK ABOUT IT – Limits to Cell Size
When a living thing grows, what happens to its cells?
What is there about growth that requires cells to divide and reproduce themselves?
What are some of the difficulties a cell faces as it increases in size?
The larger a cell becomes, the more demands the cell places on its DNA. In addition, a larger cell is less efficient in moving nutrients and waste materials across its cell membrane.
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7. Information “Overload”
Living cells store critical information in DNA.
As a cell grows, that information is used to build the molecules needed for cell growth.
As size increases, the demands on that information grow as well. If a cell were to grow without limit, an “information crisis” would occur.
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8. Information “Overload”
Compare a cell to a growing town. The town library has a limited number of books. As the town grows, these limited number of books are in greater demand, which limits access.
A growing cell makes greater demands on its genetic “library.” If the cell gets too big, the DNA would not be able to serve the needs of the growing cell.
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9. Chap 10: Cell Growth and Division 2009
Exchanging Materials
Food, oxygen, and water enter a cell through the cell membrane. Waste products leave in the same way.
The rate at which this exchange takes place depends on the surface area of a cell.
The rate at which food and oxygen are used up and waste products are produced depends on the cell’s volume.
The ratio of surface area to volume is key to understanding why cells must divide as they grow.
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10. Ratio of Surface Area to Volume
Imagine a cell shaped like a cube. As the length of the sides of a cube increases, its volume increases faster than its surface area, decreasing the ratio of surface area to volume.
If a cell gets too large, the surface area of the cell is not large enough to get enough oxygen and nutrients in and waste out.
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11. Chap 10: Cell Growth and Division 2009
Traffic Problems
To use the town analogy again, as the town grows, more and more traffic clogs the main street. It becomes difficult to get information across town and goods in and out.
Similarly, a cell that continues to grow would experience “traffic” problems. If the cell got too large, it would be more difficult to get oxygen and nutrients in and waste out.
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12. Chap 10: Cell Growth and Division 2009
Division of the Cell
Before a cell grows too large, it divides into two new “daughter” cells in a process called cell division.
Before cell division, the cell copies all of its DNA.
It then divides into two “daughter” cells. Each daughter cell receives a complete set of DNA.
Cell division reduces cell volume. It also results in an increased ratio of surface area to volume, for each daughter cell.
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13. Cell Division and Reproduction
How do asexual and sexual reproduction compare?
The production of genetically identical offspring from a single parent is known as asexual reproduction.
Offspring produced by sexual reproduction inherit some of their genetic information from each parent.
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14. Chap 10: Cell Growth and Division 2009
Asexual Reproduction
In multicellular organisms, cell division leads to growth. It also enables an organism to repair and maintain its body.
In single-celled organisms, cell division is a form of reproduction.
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15. Chap 10: Cell Growth and Division 2009
Asexual Reproduction
Asexual reproduction is reproduction that involves a single parent producing an offspring. The offspring produced are, in most cases, genetically identical to the single cell that produced them.
Asexual reproduction is a simple, efficient, and effective way for an organism to produce a large number of offspring.
Both prokaryotic and eukaryotic single-celled organisms and many multicellular organisms can reproduce asexually.
-Bacteria cells reproduce by binary fission
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16. Chap 10: Cell Growth and Division 2009
Sexual Reproduction
- In sexual reproduction, offspring are produced by the fusion of two sex cells – one from each of two parents. These fuse into a single cell before the offspring can grow.
The offspring produced inherit some genetic information from both parents.
Most animals and plants, and many single-celled organisms, reproduce sexually.
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17. Cell Division -Eukaryotes
Two main types of division:
Mitosis- results in new cells with genetic material that is identical to the genetic material of original cell
During: growth, development, repair, asexual reproduction (production of offspring from one parent)
2. Meiosis- occurs during the formation of gametes (reproductive cells, 1n), reduces the chromosome number by ½ in new cells, often combine to make 2n cells
Biology notes-Chapter 8

18. Comparing Sexual and Asexual Reproduction
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19. Chap 10: Cell Growth and Division 2009
8.2- THINK ABOUT IT
What role does cell division play in your life?
Does cell division stop when you are finished growing?
What is the role of chromosomes in cell division?
Chromosomes make it possible to separate DNA precisely during cell division
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20. Chap 10: Cell Growth and Division 2009
Chromosomes
The genetic information that is passed on from one generation of cells to the next is carried by chromosomes.
Every cell must copy its genetic information before cell division begins.
Each daughter cell gets its own copy of that genetic information.
Cells of every organism have a specific number of chromosomes.
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21. Prokaryotic Chromosomes
Prokaryotic cells lack nuclei. Instead, their DNA molecules are found in the cytoplasm.
Most prokaryotes contain a single, circular DNA molecule, or chromosome, that contains most of the cell’s genetic information.
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22. Eukaryotic Chromosomes
In eukaryotic cells, chromosomes are located in the nucleus, and are made up of chromatin.
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23. Chap 10: Cell Growth and Division 2009
Chromatin is composed of DNA and histone proteins.
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24. Chap 10: Cell Growth and Division 2009
DNA coils around histone proteins to form nucleosomes.
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25. Chap 10: Cell Growth and Division 2009
The nucleosomes interact with one another to form coils and supercoils that make up chromosomes.
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26. Biology notes-Chapter 8

27. Chromosomes structure cont:
Chromosomes contain 2 identical halves each half of the chromosome is called a chromatid
Chromatids form when the DNA makes a copy of itself before cell division
When the cell divides each ½ gets a copy
Chromatids are attached by the centromere
When DNA is not tightly packed it is call chromatin
Prokaryotes DNA is simple, circular, one chromosome, very compact to fit in the cell
Biology notes-Chapter 8

28. Biology notes-Chapter 8

29. Chromosomes Numbers Each species has a set number of chromosomes
Must know terms:
Sex chromosomes: are chromosomes that determine the sex of an organism, they may also carry genes for other characteristics (X, Y) (2 humans)
Autosomes- all non sex chromosomes (44 of humans )
Biology notes-Chapter 8

30. Chromosomes Numbers cont:
3. Homologous chromosomes- they are chromosomes that are the same sex and shape and carry genes from the same traits
4. Karyotype- photomicrograph of chromosomes in a normal dividing cell found in human cells (46 chromosomes)
22 homologous pairs of autosomes
2 sex chromosomes
Biology notes-Chapter 8

31. Karyotype
Biology notes-Chapter 8

32. Diploid (2n) and haploid (n)
If a cell is said to have 2 sets of chromosomes it is said it is diploid
They have two sex chromosomes in animals including animals
Except for reproductive cells like sperm and eggs or generally called gametes
Ex the 2n or diploid or number of chromosomes is 46 and 22 pairs
If it is haploid it contains only one set of chromosomes for example only has one set of the autosomes and sex chromosomes 23 total
Biology notes-Chapter 8

33. Biology notes-Chapter 8

34. Chap 10: Cell Growth and Division 2009
The Cell Cycle
What are the main events of the cell cycle?
During the cell cycle, a cell grows, prepares for division, and divides to form two daughter cells.
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35. The Prokaryotic Cell Cycle
The prokaryotic cell cycle is a regular pattern of growth, DNA replication, and cell division.
Most prokaryotic cells begin to replicate, or copy, their DNA once they have grown to a certain size.
When DNA replication is complete, the cells divide through a process known as binary fission.
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Chap 10: Cell Growth and Division 2009

36. Cell division in prokaryotes
Have no true nuclei or membrane-bound organelles
DNA is not coiled around proteins- it is circular attached to the inner surface of the plasma membrane like a rope attached to the inner wall of a tent
Process of cell division is Binary fission
Biology notes-Chapter 8

37. Binary fission Is the division of a prok into two offspring cells
1. DNA is copied  get two identical chromosomes
2. A new cell membrane then begins to develop between the two DNA copies
3. Cell grows till its 2x the original size
4. Cells split containing identical chromosomes
Biology notes-Chapter 8

38. Binary fission
Biology notes-Chapter 8

39. The Eukaryotic Cell Cycle
The eukaryotic cell cycle consists of four phases: G1, S, G2, and M.
Interphase is the time between cell divisions. It is a period of growth that consists of the G1, S, and G2 phases. The M phase is the period of cell division.
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40. Chap 10: Cell Growth and Division 2009
G1 Phase: Cell Growth
In the G1 phase, cells increase in size and synthesize new proteins and organelles.
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41. S Phase: DNA Replication
In the S (or synthesis) phase, new DNA is synthesized when the chromosomes are replicated.
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42. G2 Phase: Preparing for Cell Division
In the G2 phase, many of the organelles and molecules required for cell division are produced.
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43. Chap 10: Cell Growth and Division 2009
M Phase: Cell Division
In eukaryotes, cell division occurs in two stages: mitosis and cytokinesis.
Mitosis is the division of the cell nucleus.
Cytokinesis is the division of the cytoplasm.
Or a G0: stage in which the cell is mature and no longer dividing
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44. Biology notes-Chapter 8

45. What events occur during each of the four phases of mitosis?
Division of the nucleus
Occurs during cell division
Continuous process that allows for the organized distribution of cell’s copied DNA to offspring cells
Divided into four phases PMAT
1. prophase
2. metaphase
3. Anaphase
4. telophase
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46. Important Cell Structures Involved in Mitosis
Chromatid – each strand of a duplicated chromosome
Centromere – the area where each pair of chromatids is joined
Centrioles – tiny structures located in the cytoplasm of animal cells that help organize the spindle
Spindle – a fanlike microtubule structure that helps separate the chromatids
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47. Chap 10: Cell Growth and Division 2009
Prophase
During prophase, the first phase of mitosis, the duplicated chromosome condenses and becomes visible.
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48. Chap 10: Cell Growth and Division 2009
Prophase
During prophase, the first phase of mitosis, the duplicated chromosome condenses and becomes visible.
The centrioles move to opposite sides of nucleus and help organize the spindle.
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49. Chap 10: Cell Growth and Division 2009
Prophase
During prophase, the first phase of mitosis, the duplicated chromosome condenses and becomes visible.
The centrioles move to opposite sides of nucleus and help organize the spindle.
The spindle forms and DNA strands attach at a point called their centromere.
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50. Chap 10: Cell Growth and Division 2009
Prophase
During prophase, the first phase of mitosis, the duplicated chromosome condenses and becomes visible.
The centrioles move to opposite sides of nucleus and help organize the spindle.
The spindle forms and DNA strands attach at a point called their centromere.
The nucleolus disappears and nuclear envelope breaks down.
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51. Chap 10: Cell Growth and Division 2009
Metaphase
During metaphase, the second phase of mitosis, the centromeres of the duplicated chromosomes line up across the center of the cell.
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52. Chap 10: Cell Growth and Division 2009
Metaphase
During metaphase, the second phase of mitosis, the centromeres of the duplicated chromosomes line up across the center of the cell.
The spindle fibers connect the centromere of each chromosome to the two poles of the spindle.
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53. Chap 10: Cell Growth and Division 2009
Anaphase
During anaphase, the third phase of mitosis, the centromeres are pulled apart and the chromatids separate to become individual chromosomes.
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54. Chap 10: Cell Growth and Division 2009
Anaphase
During anaphase, the third phase of mitosis, the centromeres are pulled apart and the chromatids separate to become individual chromosomes.
The chromosomes separate into two groups near the poles of the spindle.
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55. Chap 10: Cell Growth and Division 2009
Telophase
During telophase, the fourth and final phase of mitosis, the chromosomes spread out into a tangle of chromatin.
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56. Chap 10: Cell Growth and Division 2009
Telophase
During telophase, the fourth and final phase of mitosis, the chromosomes spread out into a tangle of chromatin.
A nuclear envelope re-forms around each cluster of chromosomes.
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57. Chap 10: Cell Growth and Division 2009
Telophase
During telophase, the fourth and final phase of mitosis, the chromosomes spread out into a tangle of chromatin.
A nuclear envelope re-forms around each cluster of chromosomes.
The spindle breaks apart, and a nucleolus becomes visible in each daughter nucleus.
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58. Chap 10: Cell Growth and Division 2009
Cytokinesis
How do daughter cells split apart after mitosis?
Cytokinesis completes the process of cell division – it splits one cell into two.
Cytokinesis is the division of the cytoplasm.
The process of cytokinesis is different in animal and plant cells.
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59. Cytokinesis in Animal Cells
The cell membrane is drawn in until the cytoplasm is pinched into two equal parts., Cleavage furrow
Each part contains its own nucleus and organelles.
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60. Cytokinesis in Plant Cells
In plants, the cell membrane is not flexible enough to draw inward because of the rigid cell wall.
Instead, a cell plate forms between the divided nuclei that develops into cell membranes.
A cell wall then forms in between the two new membranes.
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61. Biology notes-Chapter 8

62. The Stages of the Cell Cycle
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63. Biology notes-Chapter 8