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Cell Growth and Division

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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.


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