Cells!

1. Cells! • Most cells are between 2µm and 200µm • A micrometer is 1 millionth of a meter! • Too small to be seen with naked eye

2. Your body cells are the same size as when you were born!

3. Why can’t organisms be one big giant cell?

4. Limits • Diffusion limits cell size • A cell 20 cm wide would require months for nutrients to get to the center

5. Limits • Metabolism limits cell size • Larger cells produce more waste • Larger cells require more materials

6. Surface Area : Volume • All cells want: Surface Area Volume

7. Limits • DNAlimits cell size • Larger cells need more DNA • (more things to manage)

8. So, if too big is a problem, what’s the solution? • Cellular Division!

9. Cellular Division • Process by which a growing cell divides forming two “daughter” cells

10. Keeping Cells Identical • The instructions for making cell parts are encoded in the DNA • Each new cell must get a complete set of the DNA molecules

11. DNA Replication Original DNA strand • DNA must be copied or replicated before cell division • Each new cell will then have an identical copy of the DNA Two new, identical DNA strands

12. Identical Daughter Cells Two identical daughter cells Parent Cell

13. Asexual Reproduction • A single cell dividing to make 2 new, identical daughter cells • Binary Fission • Mitosis • Occur in somatic cells (body cells) • Diploid number of chromosomes (2n)

14. Prokaryotic Chromosome • The DNA of prokaryotes (bacteria) is one, circular chromosome attached to the inside of the cell membrane

15. Steps in Binary Fission Cells increase their cell mass slightly DNA & cell components are replicated Each cell divides into 2 daughter cells

16. E. Coli Dividing by Binary Fission

17. Eukaryotic Chromosomes • All eukaryotic cells store genetic information in chromosomes • Most eukaryotes have between 10 and 50

18. Eukaryotic Chromosomes • Human body cells have 46 chromosomes or 23 identical pairs

19. Eukaryotic Chromosomes • Each chromosome is composed of a single, tightly coiled DNA molecule • Chromatin

20. Compacting DNA into Chromosomes • DNA is tightly coiled around proteins called histones

21. Chromosomes in Dividing Cells • Duplicated chromosomes are called chromatids • Held together by the centromere Called Sister Chromatids

22. DNA Vocabulary DNA in nucleus is a mass of chromatin Chromatin condenses into chromosomes …which duplicate to form sister chromatids Sister chromatids can be called a chromosome as well!

23. Karyotype • A picture of the chromosomes from a human cell arranged in pairs by size

24. Karyotype • First 22 pairs are called autosomes • Last pair are the sex chromosomes • XX female or XY male

25. Boy or Girl? The Y Chromosome Decides Y - Chromosome X - Chromosome

26. Steps in Binary Fission Review!

27. E. Coli Dividing by Binary Fission

28. Chromosomes in Dividing Cells

29. Cell Life Cycle What does the cell do in its life time? • Growth (G1) • Synthesis (S) • Growth (G2) • Mitosis • Cytokinesis

30. Mitosis • The Different Steps http://www.stolaf.edu/people/giannini/flashanimat/celldivision/crome3.swf

31. What does a cell need TO DO to divide? Interphase • Grow- gets bigger • Synthesize- copy DNA • Grow again- double its organelles • Time frame varies • Different cells divide at different rates

32. Mitosis • Division of the nucleus • Only occurs in eukaryotes • Doesn’t occur in some cells such as brain cells

33. Mitosis 1. Prophase • Nuclear envelope disappears • Chromatin condenses into chromosomes • Spindle fibers begin to attach centrioles to the chromosomes at the centromere

34. Mitosis 2) Metaphase • Chromosomes line up in the center

35. Mitosis 3) Anaphase • Sister chromatids separate • Spindles pull them apart towards the opposite ends of the cell

36. Mitosis 4) Telophase • Sister chromatids are at ends • Cytokinesis begins

37. Cytokinesis • Means division of the cytoplasm • Division of cell into two, identical halves called daughter cells • Begins interphase again

38. Cytokinesis • In animal cells, cleavage furrow forms to split cell • In plant cells, cell plate forms at the equator to divide cell

39. Cytokinesis Cleavage furrow in animal cell Cell plate in plant cell

40. Daughter Cells of Mitosis • Have the same number of chromosomes as each other and as the parent cell from which they were formed • Identical to each other, but smaller than parent cell • Must grow in size to become mature cells (G1 of Interphase)

41. Identical Daughter Cells What is the 2n or diploid number? 2 Chromosome number the same, but cells smaller than parent cell

42. Watch the clip! • http://highered.mcgraw-hill.com/sites/0073031216/student_view0/exercise13/mitosis_movie.html

43. Mitosis Video Clip

44. Regulating the Cell Cycle CYCLINS - proteins that regulate the cell cycle in eukaryotes • Internal regulators – respond to events inside the cell • Example: don’t start metaphase until chromosomes are in pairs • External regulars – respond to events outside the cell • Example: sense cells nearby

45. Regulating the Cell Cycle CANCER = disease of mitosis • Cells not responding to signals to stop dividing! • Missing density-dependent signals

46. Healthy, dividing cell Damage to cell Damage control Stop cell division Assess damage Cellular repair Successful repair Return to cell cycle Failed repair Cancer Extensive damage Cell death modified from Biology of Cancer by R.W. Phillis and S. Goodwin

47. Four Mitotic Stages • Prophase • Metaphase • Anaphase • Telophase

48. Review of Mitosis

49. Mitosis in Onion Root Tips Do you see any stages of mitosis?

50. Name the Stages of Mitosis: Early Telophase, Early prophase Early Anaphase Interphase Metaphase Late Prophase Cytokinesis Mid-Prophase Late Anaphase