Cell Growth and Division

1. Cell Growth and Division Ch. 8

2. Cells come in a variety of sizes. Diffusion limits cell size DNA content limits size What is diffusion? Cell Size and Limitation

3. Cells rely on diffusion to carry on proper functions Cells require a constant supply of glucose and oxygen Cells must constantly get rid of waste. DNA is found in all cells. The larger the cell, the greater number of enzymes DNA makes enzymes needed for the cell Diffusion and DNA limit cell size because…

4. Surface Area to Volume Ratio As the cell size increases, its volume increases 2x faster….why is this a problem? Other ways to solve the problem If cell size doubled, it would be an 8 fold increase in volume, but the surface area would only increase 4 fold. Therefore, there is not enough membrane for nutrients to flow through to keep the cell alive. Is bigger better?

5. What do you think? How will you get more membrane to compensate for the volume? They divide into 2 cells allowing for twice as much membrane to be formed. How do cells overcome this problem? 1.7a Cell growth and division are caused by complex interactions between the different kinds of molecules in the cell.

6. Growth Repair Reproduction Asexual- offspring produced only by one parent. (bacteria) Sexual- produces offspring that have a combination of genetic material from two parent organisms. 1.8a All growth and development within a cell is a consequence of an increase in cell number, size and/or products. 3 purposes of cell division

7. The Pituitary gland secretes a growth hormone that tells cells when to divide and how much. If you lack this hormone, dwarfism may occur. Rate of Cell Division 1.7b Molecules from different parts of the cells, such as hormones, can affect cell behavior.

8. Before cell division, each chromosome is replicated. Each chromosome consists of 2 identical sister chromatids. Each sister chromatid will separate from each other during cell division and go into its new cell. Centromere region also called kinetochore. When chromatin coils it becomes ______________? Structure of eukaryotic chromosomes

9. Histones are proteins that are wrapped up by DNA in the chromosome structure consisting of chromatin. This is then coiled many times within the chromosome. Chromosome Structure

11. 1.11 All organisms begin their life cycles as a single cell, and in multicellular organisms, new generations of embryonic cells form by cell division. MEIOSIS 1.1a All of the cells in your body come from a single cell that differentiates into many different cells, but they all essentially have the same genetic instructions. MITOSIS

12. Certain genes can be turned off or on at certain time. (Expresses or not expressed). The environment can influence what cells are expressed or not. This also causes cells to differentiate. 1.8b Cells differentiate from each other because of gene expression and/or environmental influences.

13. 5 phases Interphase Prophase Metaphase Anaphase Telophase The cell cycle is the repeated sequence of cell growth (interphase) followed by cell division (mitosis) The Cell Cycle Mitosis Mitosis- process of nuclear division followed by cytoplasmic division. SOMATIC CELLS (body cells)

14. Mitosis Somatic cells 1 cell division 2 daughter identical to parent Meiosis Gametes 2 divisions Daughter cells have half of genetic info as parent. Mitosis vs. Meiosis

16. Cell activities during interphase: Make ATP Repairing themselves Excreting wastes Making proteins Producing new organelles Duplicating DNA Chromatin duplicates Metabolism Cell growth in size 3 phases: G1: normal growth phase (9 hours) S: DNA is replicating (10 hours) G2: final growth in preparation for mitosis (2 hours) Interphase…a busy time (90% of cell cycle)

17. Each chromosome has two identical parts- sister chromatids that are held together by a centromere. Structure of the Chromosome

18. Chromosome number • Somatic Cells (body cells) of a particular species have the same number of chromosomes (humans have 46 or 23 pairs). • Chromosome number (n) tells how many of each type of chromosome is in the cell. • 1n (haploid), 2n (diploid)

19. Centrioles are a pair of cylindrical structures made of microtubules that are only found in animal cells and found just outside the nucleus. Spindles are cagelike structures that are made of microtubules and used to separate sister chromatids. Spindle fibers are the individual microtubules of the spindle. Other structures used..

20. Chromatin coils and becomes chromosomes. The nucleus disappears. Centrioles migrate to opposite poles of the cell. Made of microtubules. The spindle forms and attaches to the centrioles and centromere. Centrosome is where microtubules originate. Prophase- the first phase

22. Chromosomes line up along the equator Spindle fibers attach to the centromeres. Metaphase- the 2nd phase

24. Sister chromatids separate and centromeres split apart. Anaphase- the 3rd phase

26. The “reverse” of prophase Chromosomes uncoil to make chromatin Spindle fibers disappear Nucleus forms Plasma membrane begins to from between 2 nuclei. Telophase- the 4th phase

27. Cytokinesis- the division of the cytoplasm that results in two new daughter cells. CELL CLEAVAGE- split in two In plants, a cell plate forms across the equator, so the membrane doesn’t have to pinch in. ** Centrioles are not found in plant cells during cell division. The final step Mitosis in motion

28. Each new daughter cell will have complete set of genetic material. The result

29. Apply Chromosome number • Human somatic cell (46 or 23 pairs) • G1 • S • G2 • P • M • A • T

30. Cyclins are proteins that regulate the timing of the cell cycle in eukaryotic cells. Ex. Kinases end DNA replication. Internal Regulators- proteins that respond to events inside the cell. External Regulators- direct cells to speed up or slow down cell cycle. External or Internal? Make sure cell doesn’t enter mitosis until all its chromosomes have been replicated. Growth factors. Prevents cell from entering anaphase until all of its chromosomes are attached to mitotic spindle. Cell Cycle Regulators

31. Some control progression from one phase to another. Come inhibit progression. If too much or not enough is produced it can lead to cell death or cancer. Genes control enzyme production. Contact inhibition is another way the cell cycle is controlled. Cells normally stop dividing when they come into contact with each other. Enzymes control the cell 1.7a Cell growth and division are caused by complex interactions between the different kinds of molecules in the cell.

32. Cancer is thought to be due to changes in genes that make enzymes involved in the cell cycle. Cells divide when they shouldn’t. Cancer cells do not respond to the signals that regulate the growth of most cells. Oncogenes Malignant vs. Benign Neoplasm- abnormal masses of cells that have lost control over growth and cell division. Cancer cells can break away from a tumor (large mass) and travel through the blood to other areas in the body. Gene p53 normally stops the cell cycle until all chromosomes have been replicated, but if there is a defect, growth is not controlled. Cancer..A Mistake in the Cycle

33. Characteristics of cancer • Grow and divide abnormally • Cell membrane is leaky, cytoskeleton is disorganized. • Cells have a weakened capacity for adhesion and may break away to move to other sites in the body (metastasis). • Cancer cells can have lethal effects.

34. Cigarette smoke Air and water pollution UV radiation Certain viruses Cervical cancer -HPV Mesothemioma Liver cancer- Hep B Some people may be born with genetic mistakes which may cause cancer. Gene p53. Cancer is the 2nd leading cause of death in the U.S. Heart disease is #1. Other causes of cancer

35. Stem cells are unspecialized cells that have the potential to differentiate to become specialized in structure and function into a wide variety of cell types. In early embryonic development, stem cells produce every type of tissue in the body. Stem cells in bone marrow can make more than a dozen types of blood cells. Neurons are non-replaceable. Embryonic stem cell research is very controversial because the cells are taken from a human embryo. Transplants fail- different genetic info. Stem Cells

36. 3 kinds of stem cells • Totiopotent- the egg and the cells that result from early cell division. Human fertilized egg has the potential to form a whole organism. • Pluripotent- forms five days after fertilization (blastocyst- outer layer of cells and inner cell mass). Inner cells form tissue of human. • Mulitpotent- pluripotent cells specialize further to give rise to specialized cells. Present in adults. Which type of cells do you think are used for medical therapies? Why? Pluripotent

37. Cell Cycle Review • Click on the following link, then click on your book and go to Ch. 10 and take the Self-Test and do the Active Art. • Ch. 10 Review

38. Meiosis and Sexual Reproduction Ch. 9

39. Haploid (1n)- a cell with only one complete set of chromosomes (gametes or sex cells). Diploid (2n)- a cell that contains two complete sets of chromosomes. (all other cells) Meiosis….Some terms to know Which are diploid and which are haploid? How do you know sex cells (eggs and sperm) are only haploid?

40. Homologous chromosomes are pairs of chromosomes where each one is identical to the other. A tetrad is a structure containing 4 strands of DNA tightly paired together. Homologous Chromosomes come from a Tetrad

41. There is a meiosis I and II. Each are the same steps as mitosis. You begin with one diploid cell and produce 4 haploid. This gives you many different combinations of genes to be passed on. It’s all chance on the ones you get. Meiosis

42. Occurs during prophase 1 when homologous chromosomes pair up and form tetrads and exchange portions of chromatids. Crossing Over

43. 1.28a Sorting and recombination of genes in sexual reproduction, allows for a great variety of possible gene combinations. That is why no two people are alike. (Besides identical twins- why?) Meiosis Provides for Genetic Recombination

44. Why is this? So, is diversity good? Give an example. 1.46 A great diversity of species increases the chance that at least some living things will survive in the face of large changes in the environment.

45. Prophase I Metaphase I Anaphase I Telophase I Prophase II Metaphase II Anaphase II TelophaseII What occurs during each step? The Steps…Let’s review.

47. Terms to know • Zygote- diploid cell resulting from fusion of egg and sperm: a fertilized egg. • Embryo- early developmental stage of an organism that takes place within an egg, see, or body of its mother. From time of conception to eighth week of pregnancy.

48. Plant spores- 1n Originate in sporophytes (spore-producing bodies). Germinate and form gametophytes (gamete producing haploid bodies) Gamete Formation in Plants

49. Germ cells  gametes Males: spermatocyte enters meiosis and cytoplasmic division making 4 haploid spermatids that develop into sperm. Gamete formation in Animals

50. Germ cell  oocyte (immature egg). Makes 3 polar bodies and an ovum (egg) that receives most of the cytoplasm. Females