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Unit4: Cells

Structure of the cell, mitosis, meiosis

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Unit4: Cells

  1. 1. UNIT 4: CELLS
  2. 2. INDEX 1. Levels of Organisation 2. Celltheory 3. The basic Unit of Life 4. Types of Cells 5. Eukaryotic Cells 6. CellDivision
  3. 3. Atom Molecule Macromolecule Cell Organisms of the same species Many populations together All the living things on Earth H2O H, O C6H12O6 animal cell lungs horse herd of horses praire 1. Levels of Organisation
  4. 4. 2. Cell Theory (1838, Schleiden and Schwann) A cell is the smallest and simplest living thing. All cells come from other preexisting cells The cell is the basic structural and functional unit of life All living things are made up of cells Each of the cells that make up an organism can function independently although they work together in a coordinated way They can perform the three vital functions
  5. 5. 3. The Basic Unit of Life Main Parts in Every Cell Membrane It separates the cell from the environment It controls substances which enter and pass out of the cell Cytoplasm Semi-liquid interior which contains biological molecules Genetic material. DNA It controls cellular activity and gives the cell its specific characteristics
  6. 6. Nutrition The cell takes molecules from the environment and transforms them into energy or new structures, by means of the metabolism. Waste products are expelled. Metabolism = chemical reactions which take place inside cells
  7. 7. Interaction Cells: • Detect environmental changes • Respond to these changes Phagocytosis
  8. 8. Reproduction Formation of new cells. Daughter cells are always identical to their parent cell. Activities 3, 7, 12, 13 page 69
  9. 9. 4. Types of cell Size Bacteria (prokaryotic) less than 3µm Eukaryotic 5 µm - 20 µm Complexity Prokaryotic DNA floating in the cytoplasm No cellular organelles with membranes Eukaryotic DNA inside the nucleus Cellular organelles Shape
  10. 10. bacteria
  11. 11. 5. Eukaryotic cells ORGANELLE FUNCTION DRAWING Endoplasmic reticulum It makes and transports lipids and proteins Golgi apparatus It takes substances from the endoplasmic reticulum and packs them into vesicles
  12. 12. ORGANELLE FUNCTION DRAWING Lysosomes Digestion Vacuoles Store substances Ribosomes Synthesis of proteins
  13. 13. ORGANELLE FUNCTION DRAWING Centrosome Production of microtubules Centrioles (animal cell) They are involved in reproduction and cell movement Mitochondria Cellular respiration (obtain energy) ribosomes
  14. 14. ORGANELLE FUNCTION DRAWING Chloroplast (plant cell) Photosynthesis (obtain glucose) Nucleus It contains the genetic material (DNA), called chromatin Nucleoolus Synthesis of ribosomes (with chlorophyll) (double membrane)
  15. 15. ORGANELLE FUNCTION DRAWING Cilia and flagela Movement. They are controlled by the centrioles Cytoskeleton Protein fibres (tubules, microtubules… ) whick keep and give shape to the cell
  16. 16. PLANT CELL ANIMAL CELL Cell wall Chloroplast NO centrioles A big vacuole NO cell wall NO chloroplast Centrioles Small vacuoles Activities 20, 21, 24 page 75
  17. 17. 6. Cell Division (eukaryotic cells) GOAL: to produce new cells in order to: Grow and achieve embrionic development Repair body’s tissues The parent cell needs to have TWO COPIES of its genetic material original DNA identical copied DNA Daughter cells are IDENTICAL
  18. 18. Cytokinesis is the division of the cytoplasm Mitosis is the division of the nucleus in four stages: Prophase Metaphase Anaphase Telophase Interphase is the preparation for the cellular division: (it obtains nutrients, grows, copies the DNA and the centrosomes…)
  19. 19. Structure of a chromosome
  20. 20. A. Prophase The chromosomes appear (chromatin condenses) The nucleolus disappears The mitotic spindle appears (made up of protein fibers) The nuclear membrane disappears
  21. 21. B. Metaphase The chromosomes connect to the mitotic spindle with their centromeres and line up along the middle of the cell. Mitotic spindle e
  22. 22. C. Anaphase The spindle fibres contract and pull the chromatids to the opposite poles of the cell. Chromosomes’ centromeres break and sister chromatids separate.
  23. 23. D. Telophase Chromatids arrive to the poles of the cell. The mitotic spindle disappears. A nuclear membrane surrounds each group of chromosomes. The chromatids become chromatin. The nucleolus reappears.
  24. 24. E. Cytokinesis (division of the cytoplasm) ANIMAL CELLS cytoplasm streches PLANT CELLS a wall called cell plate foms 2 daughter cells
  25. 25. GOAL: To produce gametes, which are haploid cells (they just have the half of the chromosomes) n = haploid Reproductive cells 2n = diploid Somatic cells Gametes: ovum and spermatozoon The rest of the cells of the body
  26. 26. The gametes (ovum and spermatozoon) have only one of the homologous chromosomes. They are haploids (n) The cells with pairs of homologous chromosomes are diploid (2n)
  27. 27. n n + 2n zigote Each chromosome belonging to each of the pair of homologous chromosomes has been supplied by one of the parentals. Every cell of the new living being are diploid
  28. 28. + Zigote (2n) Spermatozoon (n) Ovum (n) In this example: 2n=6 n=3 In human beings 2n=46 n=23 Mitosis, mitosis…. Embryo (2n) Adult (2n) Meiosis! Double information for every character. Chromosomes are in pairs. They are called homologous chromosomes
  29. 29. Blue eyes Brown eyes A GroupB Group or The result of the meiosis is a huge genetic biodiversity, this is, all the gametes are different among them, because many combinations are possible: Blue eyes Blue eyes B Group B Group Brown eyes Brown eyes A Group A Group
  30. 30. Meiosis is the process of cell division when a diploid cell (2n) divides into 4 daughter haploid cells (n) Testicles and ovaries are somatic cells  diploid (2n) How can they produce reproductive cells, which are haploid (n)??? 46 in human beings / 6 in our example 23 in human beings / 3 in our example • 1st division  chromosomes are separated 2 cells n • 2nd division  chromatides are separated 4 cells n Meiosis includes two consecutive cell divisions:
  31. 31. 1st Division: Reduction division We obtain cells with half the number of chromosomes A. Prophase I Chromosomes appear in pairs (homologous chromosomes) A A 0 0 A A0 0 Crossing over Homologous chromosomes exchange genetic material by crossing over:
  32. 32. B. Metaphase I Pairs of homologous chromosomes become attached to the spindle fibres.
  33. 33. C. Anaphase I Complete chromosomes are pulled to each spindle pole  the number of chromosomes in every cell has been reduced to the half.
  34. 34. C. Telophase I As a result two daughter haploid cells appear. Nuclear envelopes appear and the chromosomes transform into chromatin. A short interphase takes place and the second division starts:
  35. 35. 2nd Division: Normal mitosis Chromatids are separated. At the end, cytoplasm divides, too.
  36. 36.
  37. 37. Result: 4 different haploid (n) cells (reproductive cells/gametes) 1st division 2nd division
  38. 38. Page 78 activity 26 Page 80 activity 27 Page 82 activity 3, 6, 7, 8, 9 Development of Basic Competences page 83 (both) Glossary: • Haploid • Diploid • Somatic cell • Chromatid • Homologous chromosomes • Synthesise