Chapter 6 A Tour of the Cell

1. Chapter 6 A Tour of the Cell

2. Warning!! • Much of this chapter is covered in Biology I and is considered pre-requisite knowledge. • Focus on what is new to you while you review what is already familiar.

4. Tools for Cytology (study of cells) • Cell Fractionation – break the cell apart and separate out the pieces. • Chromatography – separates mixtures based on their solubility. • Electrophoresis – separates mixtures of protein or DNA using gels and electricity.

5. Cell Fractionation

6. Chromatography • Technique for separating mixtures of chemicals. • Separates chemicals by size or degree of attraction to the materials in the medium. • Ex - paper, gas, column, thin-layer

7. Electrophoresis • Separates mixtures of chemicals by their movement in an electrical field. • Used for proteins and DNA.

8. Cell Theory • All living matter is composed of one or more cells. • The cell is the structural and functional unit of life. • All cells come from cells.

9. Types of Cells • Prokaryotic - lack a nucleus and other membrane bounded structures. • Eukaryotic - have a nucleus and other membrane bounded structures.

10. Both Have: • Membrane • Cytosol • Ribosomes (but the size is different)

11. Prokaryotic Eukaryotic Nucleus

13. Eukaryotic Prokaryotic

14. Endosymbiotic Theory •  Mitochondria and chloroplasts were once primitive bacterial cells that came to work within another cell, forming the ancestor of today’s Eukaryotes • http://highered.mheducation.com/sites/9834092339/student_view0/chapter4/animation_-_endosymbiosis.html

15. Evidence for Endosymbiosis • Membranes — Mitochondria/Chloroplasts have 2 of their own cell membranes, 1 likely derived from the original prokaryotic cell, the other from the original host cell

16. Evidence, Continued • DNA — Mitochondria/Chloroplast have their own circular DNA genome, like a bacteria's genome, but much smaller. This DNA is passed from a parent organelle to its offspring and is separate from the "host" cell's genome in the nucleus.

17. Evidence, Continued • Reproduction — Mitochondria multiply by pinching in half — the same process used by bacteria. Every new mitochondrion must be produced from a parent mitochondrion in this way; if a cell's mitochondria are removed, it can't build new ones from scratch.

18. Evidence, Continued • Mitochondria/Chloroplast are similar in size to bacteria cells • Phylogenetically, mitochondria appear to be derived from purple bacteria and chloroplast derived from photosynthetic bacteria

19. Why Are Cells So Small? • Cell volume to surface area ratios favor small size. • Nucleus to cytoplasm consideration (control). • Metabolic requirements. • Speed of diffusion.

21. Basic Cell Organization • Membrane • Nucleus • Cytoplasm • Organelles

22. AnimalCell

23. Plant Cell

24. Membrane • Separates the cell from the environment. • Boundary layer for regulating the movement of materials in/out of a cell.

25. Cytoplasm or Cytosol • Cell substance between the cell membrane and the nucleus. • The “fluid” part of a cell. Exists in two forms: • gel - thick • sol - fluid

26. Organelle • Term means "small organ”. Formed body (or compartment) in a cell with a specialized function. • Important in organizational structure of cells.

27. Organelles - function • Way to form compartments in cells to separate chemical reactions. • Keeps various enzymes separated in space.

28. You must be able to: • Identify the major organelles • Give their structure • Give their function

29. Nucleus • Most conspicuous organelle. • Usually spherical, but can be lobed or irregular in shape.

30. Structure • Nuclear membrane • Nuclear pores • Nucleolus • Chromatin

32. Nuclear Membrane • Double membrane separated by a 20-40 nm space. • Inner membrane supported by a protein matrix which gives the shape to the nucleus.

33. Nuclear Pores • Regular “holes” through both membranes. • 100 nm in diameter. • Protein complex gives shape. • Allows materials in/out of nucleus.

34. Nucleolus • Dark staining area in the nucleus. • 0 - 4 per nucleus. • Storage area for ribosomes.

35. Chromatin • Chrom: colored • - tin: threads • DNA and Protein in a “loose” format. Will form the cell’s chromosomes.

36. Nucleus - Function • Control center for the cell. • Contains the genetic instructions.

37. Ribosomes • Structure: 2 subunits made of protein and rRNA. No membrane. • Function: protein synthesis.

39. Subunits • Large: • 45 proteins • 3 rRNA molecules • Small: • 23 proteins • 1 rRNA molecule

40. Locations • Free in the cytoplasm - make proteins for use in cytosol. • Membrane bound - make proteins that are exported from the cell.

41. Endomembrane System • Membranes that are related through direct physical continuity or by the transfer of membrane segments called vesicles.

42. Endomembrane System

43. Endoplasmic Reticulum • Often referred to as ER. • Makes up to 1/2 of the total membrane in cells. • Often continuous with the nuclear membrane.

45. Structure of ER • Folded sheets or tubes of membranes. • Very “fluid” in structure with the membranes constantly changing size and shape.

46. Types of ER • Smooth ER: no ribosomes. • Used for lipid synthesis, carbohydrate storage, detoxification of poisons. • Rough ER: with ribosomes. • Makes secretory proteins.

47. Golgi Apparatus or Dictyosomes • Structure: parallel array of flattened cisternae. (looks like a stack of Pita bread) • 3 to 20 per cell. • Likely an outgrowth of the ER system.

49. Function of Golgi Bodies • Processing - modification of ER products. • Distribution - packaging of ER products for transport.

50. Golgi Vesicles • Small sacs of membranes that bud off the Golgi Body. • Transportation vehicle for the modified ER products.