Chapter 5 The human organism and the perpetuation of life.

1. Chapter 5The human organism and the perpetuation of life. Topics: The cell and its functions Cell division (mitosis & meiosis) Tissues, organs and systems The Reproductive System

2. About Cells • The cell is the basic unit of structure and function in living things • Cells are usually microscopic, but range from the size of a bacteria to the size of an unfertilized ostrich egg. • Living things contain one or more cells • Protozoans contain a single cell • Humans contain billions of cells

3. CELL PARTS • The various parts of cells are known collectively as CELL PARTS. • Cell parts are structures inside a cell that are too small to be living, but which together allow a cell to live. • Cell parts include: • Membranes, that surround the cell and nucleus. • Filaments, tubules and fibres that • Macromolecules, like the DNA of chromosomes. • Fluids, like the cytoplasm. • Organelles and other structures inside the cell.

4. Three Main Parts of a Cell • A cell usually has three distinct areas or layers: • The membrane • The Cytoplasm & Organelles • The nucleus & Chromosomes Membrane Cytoplasm (with organelles) Nucleus (with chromosomes)

5. Function of the Cell Membrane • The cell membrane is a flexible barrier that that surrounds the cell and allows the cell to interact with its environment • Forms a protective barrier • Helps absorb nutrients and useful substances • Helps eliminate wastes and other materials produced inside cells

6. Drawing of a cell membrane Copy the “simplified diagram” from the blackboard

7. Part 2: The Cytoplasm & Organelles • Together, the cytoplasm and organelles are sometimes called protoplasm • The cytoplasm is the liquid portion of the cell. • It is a complex mixture of materials: water, gases, wastes, nutrients, raw materials • The Organelles • Suspended in the cytoplasm are many tiny structures called organelles. Each organelle has a specific function.

8. The Organelles • Mitochondria (sing. mitochondrion). • Endoplasmic reticulum • Rough • Smooth • Ribosomes • Golgi Apparatus • Lysosomes • Vacuoles

9. Mitochondria • The mitochondrion is the powerhouse of the cell. Here chemical energy is released by the break down of food particles. • It is a bean-shaped organelle with an internal membrane folded into many “cristae” . I am very energetic! And cute as a bean too!

10. Endoplasmic Reticulum • The “ER” or Endoplasmic Reticulum is a network of tubes and membranes that runs through the cell. Its purpose is to transport materials quickly through the cell • Rough ER • Has ribosomes • Smooth ER • Has no ribosomes ER Transport system at your service! For when it absolutely, positively has to get to the ribosomes quick as possible.

11. Ribosomes • Very tiny, round organelles associated with protein synthesis • They help manufacture the cell’s proteins. We are very small, like beads. Sometimes we hang around the endoplasmic reticulum

12. GolgiApparatus(A.K.A. Golgi body or Golgi complex) • A network of membranes, similar in appearance to the ER • Its purpose is to modify and “package” proteins that will be secreted. • Also makes digestive enzymes I look like sort of like a stack of pancakes with blobs of syrup falling off!

13. Lysosomes & Vacuoles • These are storage areas within a cell • Lysosomes hold digestive enzymes that help the cell metabolize food. When a cell dies, the digestive enzymes help dissolve the dead cell • Vacuoles store food or water Let’s get together And have a feast! I’ve got the digestive enzymes And I’ve got the food

14. Part 3: The Nucleus • The nucleus consists of: • The nuclear membrane or envelope (with tiny nuclear pores in it) • The nucleoplasm • The chromatin material • AKA chromosomes • The nucleolus Hey! I am, like, in control, man! All the organelles get their instructions from me.

15. Exercise • Colour, label and give the functions of the cell drawing.

16. Typical Human Cell

17. Cell Membrane • Smooth ER • Cytoplasm • Mitochondrion • Ribosome • Nucleus • Golgi apparatus • Lysosome • Endocytosis / Exocytosis • Nucleoplasm or “matrix” (containing chromatin) • Nucleolus • Nuclear membrane “envelope” (with nuclear pores in it) • Rough ER

18. DNA a helix is a spiral shape, similar to a spring. DNA is a molecule, shaped like a double helix, usually found inside the cell’s nucleus. • Facts about DNA • Chromosomes are made of DNA • Genetic information is stored on DNA • DNA is the only large molecule that is able to copy itself. • Trivia: • DNA stands for deoxyribonucleic acid. A Helix

19. Carbon atom (gray) Hydrogen atom (white) Phosphorus atom (orange) Oxygen atom (red) Nitrogen Atom (blue) Portion of a Model of a DNA Molecule Simplified drawing of a DNA Molecule DNA contains carbon, hydrogen, oxygen, nitrogen and phosphorus The atoms are arranged into a sugar-phosphate backbone, and four types of nitrogen-containing bases.

20. Some people compare the structure of DNA to a twisted ladder. • The sugar and phosphate form the sides, and the base pairs make the rungs or steps.

21. Genes • A Gene is a segment of DNA that contains the genetic information to carry out a particular job. • That is, to make a particular protein or to control a particular feature. • A Genomeis a complete set of genetic information. • Enough information to make a complete body and all the cells in it. • A genome can contain thousands of genes

22. Genetic Diversity • Genetic Diversityis the differences between individuals, achieved by all possible genetic variations of a particular species. • All organisms have different individuals. • The more the differences, the greater the genetic diversity.

23. Assignments • Textbook: • Read pp. 125 to 127 • You may try questions 1 to 7 on p. 152 • Workbook • Do pages 67 to 70

24. Mitosis & Meiosis Topics: Mitosis Overview Meiosis Overview Mitosis vs. Meiosis

25. Cell Cycle The life of a cell: • Cell grows • Prepares for division (mitosis), • Divides to daughter cells, • Cycle begins again OR • Cell Dies

26. Overview of Mitosis Spindle forming Centrioles Centromere Chromatin Centriole Nuclear envelope Chromosomes (paired chromatids) Interphase Prophase Spindle Cytokinesis Centriole Metaphase Individual chromosomes Telophase Anaphase Nuclear envelope reforming

27. 2 Main Events of the Cell Cycle • Interphase: Cell grows & prepares for Mitosis (see previous slide for diagram) • Prepares 2 ways • Replicates chromosomes • “Tools” for mitosis are produced • Mitosis: Cell divides to form two genetically identical cells • One copy of chromosomes goes into each new cell

28. Mitosis main points • Starts as diploid • two copies of each chromosome (total=46 in humans) • Ends as diploid • One diploid parent cell makes two identical diploid copies of itself. (total=46 in humans) • Very small portion of cell life spent in mitosis (6%) • All living and growing cells undergo mitosis

29. Meiosis

30. Meiosis main points • Meiosis Enables sexual reproduction • Starts with diploid cells • Two of each chromosome type (46 in humans) • Ends with haploid sperm or egg cells. • Only one copy of each chromosome (23 in humans) • Only cells in testicles and ovaries undergo meiosis. • Meiosis increases genetic diversity due to crossing over of genes, and the mixing of two different sets of genes after fertilization

31. Mitosis in Detail • Remember: • Mitosis is normal cell division • It is part of the cell cycle The Rest of the CELL CYCLE Cell Division (MITOSIS)

32. Phases in the Cell Cycle I P M A T Remember: = INTERPHASE Preparing for Mitosis Where’s my Pee MAT? It will help you keep track of the 5 main phases of a cell’s life = PROPHASE Undergoing Mitosis = METAPHASE = ANAPHASE = TELOPHASE (and cytokinesis)

33. The Cell Cycle Cytokinesis: The cell splits into two new cells Prophase: The nuclear envelope disapears and the centrioles migrate to opposite poles of the cell Metaphase: The chromosomes line up near the middle of the cell (equatorial plane) and spindle fibres attach to them . Interphase: The Cell grows and the DNA replicates. The cell prepares to divide. Anaphase: The chomatids split into new chromosomes, and the new chromosome migrate to opposite poles Telophase: The chromosomes reach the poles, new nuclei begin to form, the cell prepares to split. G1 S G2 M1 M2 M3 M4

34. Mitosis: Short video

35. Interphase • Interphase: Cell prep for mitosis (G1, S, G2) • Cell spends ~94% of life in interphase

36. Photograph of Interphase

37. Stages of Mitosis Prophase: (Prep Phase) • Chromosomes coil and become visible • Nuclear membrane breaks down • Spindle fibers assemble

38. Photo: Early Prophase Chromosomes

39. Stages of Mitosis • Metaphase (Middle) • Chromosomes line up in the middle of cell • Spindle fibers bind to the centromere

40. Photo: Metaphase Spindle (fibers) Centrosome Chromosomes Equatorial Plane

41. Stages of Mitosis • Anaphase (Apart) • Spindle fibers pull chromosomes to opposite sides of the cell

42. Photo: Anaphase Centrosome Chromosomes Equatorial Plane

43. Stages of Mitosis • Telophase (Two) • Cell begins to split into two cells • Nuclear membranes reform

44. Photo: Telophase & Cytokinesis Cleavage furrow Nucleus forming Cells Divide

45. Stages of Mitosis • Cytokenisis • Cytoplasm is split in half • Each cell has identical chromosomes Annoying Mitosis Song video

46. During your lifetime, mitosis has created the billions of cells of cells that make up your body. • Mitosis is simple and nearly flawless (errors in mitosis are extremely rare) • Mitosis gives each cell its own copy of all your genetic information (your DNA) • Simple organisms (like the amoeba) can even reproduce by mitosis.

47. If mitosis works so well, why do we need meiosis? • Sexual reproduction helps a species survive. • It allows traits from two individuals to be mixed, giving greater diversity. • Greater diversity gives a species a better chance of surviving hard times.

48. In order to have sexual reproduction, there must be a way of reducing chromosome numbers. • You have 46 chromosome, your spouse has 46 chromosomes • If meiosis did not occur, your children would have 92 chromosomes • Your grandchildren would have 184 chromosomes • Your great-grandchildren 368, and so on… • This would soon lead to genetic problems like birth defects or bad mutations.

49. Meiosis strips away half of the chromosomes • In humans this produces eggs and sperm with only 23 chromosomes (instead of 46) • Fertilization restores the chromosomes • When a human egg is fertilized, it gets 23 chromosomes from the mother and 23 from the father, restoring the normal 46

50. Meiosis 1st Metaphase: The chromosomes line up near the middle of the cell (equatorial plane) and spindle fibres attach to them . 1st Prophase: The nuclear envelope disapears and the centrioles migrate to opposite poles of the cell Interphase: The Cell grows and the DNA replicates. The cell prepares to divide. G1 S G2 MEIOSIS