1. Cell Growth and Division
Chapter 5
Cell Growth and Division

2. Think about baking cookies…
If you want to make two batches of cookies, what do you need to do to the recipe?
Double all of the ingredients in the recipe
For cells to be functional after division, what needs to be present?
A complete set of DNA, organelles, cell membrane, and a cell wall if it is a plant cell.

3. 5.1 The Cell Cycle Why do you always have to cut your hair and nails?
Growth is caused by new cells being made

4. The cell cycle has four main stages
The cell cycle is a regular pattern of growth, DNA duplication, and cell division that occurs in eukaryotic cells.
Four stages: Gap 1, Synthesis, Gap 2, Mitosis
Gap 1, Synthesis, and Gap 2 make up a phase called interphase

5. 1. Gap 1 (G1) First stage of the cell cycle.
2. Cells carry out normal functions during this stage.
Example: If it is a muscle cell it contracts to move joints.
During this phase the cell is increasing in size and making organelles.
Cells need specific signals from other cells telling them if they are ready to move onto the synthesis stage.

6. 3. Synthesis (S) Second stage 4. Cell makes a copy of its DNA
By the end of the S stage, the cell nucleus contains two complete sets of DNA
Two identical copies of DNA
Original DNA

7. 5. Gap 2 (G2)
Third stage
Cells continue to (6) carry out their normal functions during this stage, and additional growth occurs.
There is also a critical checkpoint at this stage.

8. 7. Mitosis (M) 8. Cell Division Fourth stage Includes two processes:
Division of the cell nucleus and its contents
During mitosis the nuclear membrane dissolves, the duplicated DNA condenses around proteins and separates, and two nuclei form.
10.Cytokinesis:
Process that divides the cell cytoplasm
Results in two daughter cells that are genetically identical to the original cell.

9. Predict:
What might happen if the G2 checkpoint stopped working in cells?
Cells may be the wrong size, have damaged DNA and fail to divide.

10. Cells divide at different rates
Prokaryotic cells typically divide much faster than eukaryotic cells.
Why?
They do not have membrane-bound organelles or a cytoskeleton
In human cells, S, G2, and M phases typically take 12 hours
G1 phase varies widely
Cells that rarely divide are thought to go through a phase called G0

11. Infer
Do you think a skin cell would have a long G1 or a short G1? Why?

12. Cell size is limited Cells have upper and lower size limits
Lower limit depends on the ability to hold organelles
Some cells must be large, but have unique shapes
Upper limit depends on the ratio of cell surface area to volume
Volume increases faster than surface area

13. Connect
Which has the larger ratio of surface area to volume, a tennis ball or a soccer ball? Explain your reasoning.
A tennis ball, because volume increases more rapidly than does surface area as a ball gets larger.

14. Check for understanding
During which stage of the cell cycle is the DNA copied?
Synthesis (S)
Which stages of the cell cycle generally require about the same amount of time in all human cells?
Synthesis, Gap 2, and Mitosis
What limits the maximum size of a cell?
Ratio of surface area to volume

15. Cancer Case Study
Read pages with your partner, alternating back and forth for each paragraph.
As you read, think of 4-5 words that you feel are the most important for describing what the article is about
Write each word on the blank side of a notecard (one per notecard)
Start reading
Identify terms that support your main term on the notecard and make a web.
Find another group and choose the 4 most important words out of both groups.
Write a summary using at least 4 of your cards on the board.

16. Mitosis and Cytokinesis
Section 5.2
Mitosis and Cytokinesis

17. Cell Division The process by which a cell divides into two new cells
Why do cells need to divide?
Living things grow by producing more cells, NOT because each cell increases in size.
Repair of damaged tissue
If cell gets too big, it cannot get enough nutrients into the cell and wastes out of the cell.

18. Chromosomes condense at the start of mitosis
A chromosome is one long continuous thread of DNA
Your body cells have 46 chromosomes each
DNA wraps around proteins that help condense it
DNA double helix
DNA and histones
Chromatin
Supercoiled DNA

19. Chromosomes condense at the start of mitosis
Loose DNA is called chromatin
DNA warps around histones which help organize the chromosomes
DNA double helix
DNA and histones
Chromatin
Supercoiled DNA

20. Chromosomes condense at the start of mitosis
DNA plus proteins are called chromatin
One half of a duplicated chromosome is a chromatid
Sister chromatids are held together at the centromere
Telomeres protect the DNA and do not include genes
Condensed, duplicated chromosome
chromatid
telomere
centromere

21. Mitosis and cytokinesis produce two genetically identical daughter cells
1. Interphase prepares the cell to divide
DNA is duplicated during interphase
Parent cell
centrioles
spindle fibers
centrosome
nucleus with
DNA

22. Prophase
2. During prophase, chromosomes condense and spindle fibers form

23. Metaphase
3. During metaphase, chromosomes line up in the middle of the cell

24. Anaphase
4. During anaphase, sister chromatids separate to opposite sides of the cell

25. Telophase
5. During telophase, the new nuclei form and chromosomes begin to uncoil

26. Cytokinesis 6. Differs in animal and plant cells 7.
In animal cells, the membrane pinches closed.
In plant cells, a cell plate forms.

27. DNA photographed for the first time!

28. Regulation of the Cell Cycle
Section 5.3
Regulation of the Cell Cycle

29. Internal and external factors regulate the cell cycle
Internal factors:
Often triggered by external factors.
Two of the most important internal factors are kinases and cyclins.
Kinases: Increases the energy of the target molecule or changes its shape.
Cyclins: Proteins that activate kinases for the cell cycle

30. Internal and external factors regulate the cell cycle
External factors come from outside the cell.
They include cell-cell contact and other physical signals.
Include chemical signals such as growth factors.
Growth factors may stimulate growth in a wide variety of cells or may stimulate only specific cells to divide.

31. Carcinogens Carcinogens are substances known to promote cancer.
Examples:
Tobacco smoke
Air pollutants
Radiation
Mutated genes
Standard cancer treatments typically kill both cancerous and healthy cells.
Chemotherapy
Radiation Therapy

32. Cell division is uncontrolled in cancer
Characterized by uncontrolled cell division.
Continue to divide despite cell-cell contact or lack of growth factors.
Tumors:
Disorganized clumps of cancer cells that do not carry out specialized functions needed by the body.
Malignant tumors metastasize, or break away, and can form more tumors.
Benign tumors remain clustered and can be removed.
cancer cell
bloodstream
normal cell

33. Apoptosis Programmed cell death A normal feature of healthy organisms
Caused by a cell’s production of self-destructive enzymes
Occurs in development of infants
webbed fingers

34. Section 5.4
Asexual Reproduction

35. Binary fission is similar in function to mitosis
Asexual reproduction of a single-celled organism by division into two roughly equal parts.
Binary fission produces two daughter cells genetically identical to the parent cell.
Binary fission occurs in prokaryotes.
parent cell
DNA
duplicates
cell begins
to divide
daughter
cells

36. Some eukaryotes reproduce through mitosis
Budding forms a new organism from a small projection growing on the surface of the parent.

37. Some eukaryotes reproduce through mitosis
Fragmentation is the splitting of the parent into pieces that each grow into a new organism.
Vegetative reproduction forms a new plant from the modification of a stem or underground structure on the parent plant.

38. Asexual Reproduction
Asexual reproduction is the creation of offspring from a single parent.
Genetically identical offspring from one parent organism.
Does not involve fusion of gametes.

39. Environment determines what form of reproduction is most advantageous.
Asexual reproduction is an advantage in consistently favorable conditions.
All organisms can potentially reproduce.
Organisms to not need to spend resources finding a mate.
Sexual reproduction is an advantage in changing conditions.

40. Section 5.5
Multicellular Life

41. Multicellular organisms depend on interactions among different cell types.
Cells: Smallest, most basic structural unit of life; typically become specialized
Tissues: Groups of cells that work together to perform a similar function
Organs: groups of tissues that work together to perform similar or related functions
Organ Systems: organs that carry out similar functions
vascular
tissue
leaf
stem
lateral
roots
primary
root
SYSTEMS
root system
shoot system
CELL
TISSUE
ORGAN

42. Specialized cells perform specific functions.
Cells develop into their mature forms through the process of cell differentiation.
Cells differ because different combinations of genes are expressed.
A cell’s location in an embryo helps determine how it will differentiate.
Outer: skin cells
Middle: bone cells
Inner: intestines

43. Stem cells are unique body cells.
Defining Characteristics: Stem cells have the ability to
divide and renew themselves
remain undifferentiated in form
develop into a variety of specialized cell types

44. Stem cells are classified into three types.
totipotent, or growing into any other cell type
pluripotent, or growing into any cell type but a totipotent cell
multipotent, or growing into cells of a closely related cell family

45. Possible uses: The use of stem cells offers many currently realized and potential benefits.
Stem cells are used to treat leukemia and lymphoma.
Stem cells may cure disease or replace damaged organs.
Stem cells may revolutionize the drug development process.

46. Stem cells come from adults and embryos.
Adult stem cells can be hard to isolate and grow.
The use of adult stem cells may prevent transplant rejection.
The use of embryonic stem cells raises ethical issues
Embryonic stem cells are pluripotent and can be grown indefinitely in culture.
First, an egg is fertilized by a sperm cell in a petri dish. The egg divides, forming an inner cell mass. These cells are then removed and grown with nutrients. Scientists try to control how the cells specialize by adding or removing certain molecules.