Understanding Cell Size Limits and Mitosis in the Cell Cycle

1. Topic 4Cell Growth & Division Chapter 10: The Cell Cycle and Mitosis BIOLOGY- WAUGAMAN - LATHROP

2. Twilight Mitosis • https://www.youtube.com/watch/?v=sOM_u1PY0s0

3. 10.1 Cell Growth, Division, and reproduction Limits to Cell Size • Cells come in all shapes and sizes…the smallest are bacteria cells…the largest is the ostrich egg…. …the largest human cell is the female egg

4. 10.1 Cell Growth, Division, and reproductionFactors Affecting Cell Size Three things that limit cell size: • Rate of Diffusion • Amount of DNA • Surface Area-to-Volume ratio of cell

5. 10.1 Cell Growth, Division, and reproduction1. DiffusionLimits Cell Size • Nutrients, oxygen, water & wastes must pass through the membrane efficiently. • Diffusion is fast and efficient over a short distance. • Slow and inefficient as distance becomes greater. • Because of the slow rate, organisms cannot be just one giant cell. The organelles would “starve” waiting for necessary nutrients to “diffuse“ to them, and wastes would build up in the cell.

6. 10.1 Cell Growth, Division, and reproduction2. DNALimits Cell Size • We talked about how the nucleus contains the code or blueprints for proteins... • Proteins are used throughout the cell to perform various cell functions. • There’s a limit to how fast the nucleus can instruct the ribosomes to make the proteins. • The cell cannot survive unless there is enough DNA to support the protein needs of the cell. I Love Lucy Chocolate Factory

7. 10.1 Cell Growth, Division, and reproduction3. Surface Area to Volume Ratio • As a cell’s size increases, its volume increases much faster than its surface area. • Increased volume means the cell needs more nutrients and produces more waste • However, if the surface area does not increase relative to the volume, the surface area cannot support the volume’s needs… and the cell will die!

8. 10.1 Cell Growth, Division, and reproductionDNA Structuresof Cell Cycle • Chromatin – long, uncoiled strands of DNA…this is the DNA structure during most of the cell’s life. • Chromosomes – Tightly coiled structure of DNA, forms before cell replication. • Carries the genetic material (DNA) that is copied and passed from generation to generation of cells. • This genetic material is crucial to the identity of the cell. Chromatin Chromosomes

9. 10.1 Cell Growth, Division, and reproductionDNA Structuresof Cell Cycle • Sister Chromatids– 2 halves of the duplicated chromosomes. • Sister chromatids and the DNA they contain are exact copies of each other. • They are formed when DNA is replicated (copied) during interphase • Centromere – a protein structure that holds the two sister chromatids together. • Plays a role in chromosome movement during mitosis. sister sister Centromere

10. 10.1 Cell Growth, Division, and reproductionPurpose of Sister Chromatids • Before Cell Replication the cell COPIES all the strands of DNA in the nucleus. • All the strands of DNA now coil up to form chromosomes • The copies for each chromosome are “tied” together by the centromere. • Why copy DNA? • Why does DNA coil into a chromosome? • Why tie together copies?

11. 10.1 Cell Growth, Division, and reproductionChromosome Numbers • Organism with most chromosomes is a fern with 630 different chromosomes. • 2n =1,260 strands of DNA • Humans have 23 pairs of chromosomes. • Haploid (1n) = 23 different chromosomes • Diploid (2n) = 23 pair = 46 chromosomes • 23 chromosomes from mom and 23 chromosomes from dad

12. 10.1 Cell Growth, Division, and reproductionThe Cell Cycle • The series of events that occurs during the life of a cell is called the Cell Cycle. • Why Do Cells Divide? • Reproduction • Growth • Repair

13. 10.2 The Process of cell Division Stages of Cell Cycle • Interphase • Prophase • Metaphase • Anaphase • Telephase • Cytokinesis • IPMAT Phases OF MITOSIS

14. 10.2 The Process of cell DivisionINTERPHASE – not very “interesting” • Interphase is when a Cell is in a “working” phase, performing normal cell functions (metabolism) • At the end of Interphase Organelles (including the chromosomes) double in number, to prepare for division.

15. 10.2 The Process of cell DivisionINTERPHASE • Longest part of the cell cycle…broken into Stages: • G1 (Growth 1) - The cell grows in size • S (Synthesis) – DNA copies • G2(Growth 2) – Cell prepares for division

16. 10.2 The Process of cell DivisionCell in Interphase • Normal metabolic activities • DNA is chromatin • Nuclear Membrane Present

17. 10.2 The Process of cell DivisionMitosis – Cell Division • Process by which a Somatic (BODY) cell divides into 2 identical daughter cells. • Each new cell has a complete set of chromosomes. Why is this important? • In nuclear division (MITOSIS), the number of chromosomes remains the same. Why is this important? • Phases of Mitosis: • Prophase • Metaphase • Anaphase • Telophase

18. 10.2 The Process of cell DivisionSummary of Mitosis • One parent cell divides to create 2 daughter cells that are identical in DNA and Function as the original cell. Cytokinesis This Organism’s Cells have 2 different Chromosomes

19. 10.2 The Process of cell DivisionMitosis - #1 PROPHASE Events & Structures in Prophase: • Spindle fibers form “Protein Ropes” • Centrioles move to opposite poles “Anchors” • Chromosomes become visible “Coil Up” • Nuclear membrane begins to disappear • Nucleolus has disappeared • In plants, the spindles form without the centrioles.

20. 10.2 The Process of cell DivisionPROPHASE EARLY PROPHASE LATE PROPHASE

21. 10.2 The Process of cell DivisionMitosis - #2 METAPHASE • Chromosomes line up along the equator. • Spindles attach to centromeres.

22. Chromatids 10.2 The Process of cell DivisionMitosis - #3 ANAPHASE • Centromeres divide or pulled Apart • Chromatids separate and move to opposite poles

23. 10.2 The Process of cell DivisionMitosis - #4 TELOPHASE • Nuclear membrane begins to form around each group of chromosomes. • Chromosomes unwind into chromatin • Cytokinesis begins

24. 10.2 The Process of cell DivisionCYTOKINESIS • The process by which the cytoplasm divides and one cell becomes two individual cells. • The process is different in plants and animals • Animals - cell pinches inward • Plants - a new cell wall forms between the two new cells…this wall is called a cell plate.

25. 10.2 The Process of cell DivisionCYTOKINESIS 2 Identical Daughter Cells Result from Cytokinesis Interphase Begins again in each new cell

26. 10.2 The Process of cell DivisionResults of Mitosis • A process of Mitosis guarantees genetic continuity. • One cell produces two new identical cells • These two cells will do the same (in structure and function) as the parent cell.

27. 10.2 The Process of cell DivisionVisualizing the Cell Cycle

28. 10.3 regulating the Cell Cycle Controls on Cell Division • How is the cell cycle regulated? • The cell cycle is controlled by regulatory proteins both inside and outside the cell.

29. The controls on cell growth and division can be turned on and off. For example, when an injury such as a broken bone occurs, cells are stimulated to divide rapidly and start the healing process. The rate of cell division slows when the healing process nears completion. 10.3 regulating the Cell Cycle

30. 10.3 regulating the Cell CycleThe Discovery of Cyclins • Cyclins are a family of proteins that regulate the timing of the cell cycle in eukaryotic cells. • This graph shows how cyclin levels change throughout the cell cycle in fertilized clam eggs.

31. 10.3 regulating the Cell CycleRegulatory Proteins • Internal regulators are proteins that respond to events inside a cell. They allow the cell cycle to proceed only once certain processes have happened inside the cell. • External regulators are proteins that respond to events outside the cell. They direct cells to speed up or slow down the cell cycle. • Growth factors are external regulators that stimulate the growth and division of cells. They are important during embryonic development and wound healing.

32. 10.3 regulating the Cell CycleApoptosis • Apoptosis is a process of programmed cell death. • Apoptosis plays a role in development by shaping the structure of tissues and organs in plants and animals. For example, the foot of a mouse is shaped the way it is partly because the toes undergo apoptosis during tissue development.

33. 10.3 regulating the Cell CycleCancer: Uncontrolled Cell Growth • How do cancer cells differ from other cells? • What is cancer video clip

34. Cancer: Uncontrolled Cell Growth • How do cancer cells differ from other cells? • Cancer cells do not respond to the signals that regulate the growth of most cells. As a result, the cells divide uncontrollably.

35. Cancer is a disorder in which body cells lose the ability to control cell growth. Cancer cells divide uncontrollably to form a mass of cells called a tumor. 10.3 regulating the Cell Cycle

36. 10.3 regulating the Cell Cycle • A benign tumor is noncancerous. It does not spread to surrounding healthy tissue. A malignant tumor is cancerous. It invades and destroys surrounding healthy tissue and can spread to other parts of the body. The spread of cancer cells is called metastasis. Cancer cells absorb nutrients needed by other cells, block nerve connections, and prevent organs from functioning.

37. 10.3 regulating the Cell CycleWhat Causes Cancer? • Cancers are caused by defects in genes that regulate cell growth and division. • Some sources of gene defects are smoking tobacco, radiation exposure, defective genes, and viral infection. • A damaged or defective p53 gene is common in cancer cells. It causes cells to lose the information needed to respond to growth signals.

38. 10.3 regulating the Cell CycleTreatments for Cancer • Some localized tumors can be removed by surgery. • Many tumors can be treated with targeted radiation. • Chemotherapy is the use of compounds that kill or slow the growth of cancer cells.

39. 10.3 regulating the Cell CycleTHINK ABOUT IT The human body contains hundreds of different cell types, and every one of them develops from the single cell that starts the process. How do the cells get to be so different from each other?

40. 10.4 Cell Differentiation From One Cell to Many • How do cells become specialized for different functions? • During the development of an organism, cells differentiate into many types of cells.

41. All organisms start life as just one cell. Most multicellular organisms pass through an early stage of development called an embryo, which gradually develops into an adult organism. 10.4 Cell Differentiation

42. During development, an organism’s cells become more differentiated and specialized for particular functions. For example, a plant has specialized cells in its roots, stems, and leaves. 10.4 Cell Differentiation

43. 10.4 Cell DifferentiationDefining Differentiation • The process by which cells become specialized is known as differentiation. • During development, cells differentiate into many different types and become specialized to perform certain tasks. • Differentiated cells carry out the jobs that multicellular organisms need to stay alive.

44. 10.4 Cell DifferentiationMapping Differentiation • In some organisms, a cell’s role is determined at a specific point in development. • In the worm C. elegans, daughter cells from each cell division follow a specific path toward a role as a particular kind of cell.

45. 10.4 Cell DifferentiationDifferentiation in Mammals • Cell differentiation in mammals is controlled by a number of interacting factors in the embryo. • Adult cells generally reach a point at which their differentiation is complete and they can no longer become other types of cells.

46. 10.4 Cell DifferentiationStem Cells and Development • What are stem cells? • The unspecialized cells from which differentiated cells develop are known as stem cells.

47. One of the most important questions in biology is how all of the specialized, differentiated cell types in the body are formed from just a single cell Biologists say that such a cell is totipotent, literally able to do everything, to form all the tissues of the body. Only the fertilized egg (ZYGOTE) and the cells produced by the first few cell divisions of embryonic development are truly totipotent. 10.4 Cell Differentiation

48. 10.4 Cell DifferentiationHuman Development • After about four days of development, a human embryo forms into a blastocyst, a hollow ball of cells with a cluster of cells inside known as the inner cell mass. • The cells of the inner cell mass are said to be pluripotent, which means that they are capable of developing into many, but not all, of the body's cell types.

49. 10.4 Cell DifferentiationStem Cells • Stem cells are unspecialized cells from which differentiated cells develop. • There are two types of stem cells: embryonic and adult stem cells.

50. 10.4 Cell DifferentiationEmbryonic Stem Cells • Embryonic stem cells are found in the inner cells mass of the early embryo. • Embryonic stem cells are pluripotent. • Researchers have grown stem cells isolated from human embryos in culture. Their experiments confirmed that embryonic stem cells have the capacity to produce most cell types in the human body.