Chapter 6: A Tour of the Cell

1. Chapter 6: A Tour of the Cell

2. The Beginning First Living Cells - 1674 First Cells - 1665 Leeuwenhoek’s Microscope Hooke’s Microscope

3. Studying Cells • Microscopes • Light • Electron • Cell Fractionation

4. The Light Microscope • Light is transmitted through the specimen • Magnified and focused using lenses • Maximum magnification is around 1000X • Sample can be stained to see various organelles and internal structures • Can look at preserved or living specimens

5. The Light Microscope • Light is transmitted through the specimen • Magnified and focused using lenses • Maximum magnification is around 1000X • Sample can be stained to see various organelles and internal structures • Can view preserved or living specimens

6. Micrograph from Light Microscope Euglena, LM 1000X

7. Resolution

8. The Electron Microscope • Two types: Scanning (SEM) and Transmission (TEM) • Electrons are passed through the specimen (TEM) or bounce off the surface (SEM) • Maximum magnification is around 100,000X • High resolution • All specimens MUST BE preserved – no living cells

9. Micrograph from Transmission Electron Microscope

10. 1 m Figure 6.8bc Cell wall Vacuole Nucleus Mitochondrion A single yeast cell(colorized TEM)

11. Micrograph from Scanning Electron Microscope

14. TECHNIQUE Cell Fractionation Homogenization Tissuecells • Technique used to separate organelles and major structures from one another • Involves centrifugation • Heavier components are pushed to the bottom of the test tube • Can separate out using sequential centrifugations at increasing speeds Homogenate Centrifuged at1,000 g(1,000 times theforce of gravity)for 10 min Fig. 6-5 Centrifugation Supernatantpoured intonext tube Differentialcentrifugation 20,000 g 20 min 80,000 g 60 min Pellet rich innuclei andcellular debris 150,000 g 3 hr Pellet rich inmitochondria(and chloro-plasts if cellsare from a plant) Pellet rich in“microsomes”(pieces of plasmamembranes andcells’ internalmembranes) Pellet rich inribosomes

15. Cell Theory • All organisms are made of cells • All cells come from cells

16. Features of All Cells • Plasma membrane - selective barrier • Cytoplasm – semifluid substance containing organelles and other components • DNA – genetic information • Ribosomes – protein making structures

17. Prokaryotes vs. Eukaryotes • DNA Location: • Proks: nucleoid region • Euks: nucleus • Organelles • Proks: no true organelles (no internal membranes) • Euks: membrane-bound organelles • Size • Proks: smaller • Euks: larger

18. Prokaryotic cell Nucleoid region Colorized TEM 15,000 Nucleus Organelles Eukaryotic cell

19. Surface area increases while total volume remains constant 5 1 1 Total surface area [Sum of the surface areas (height  width) of all boxes sides  number of boxes] 150 750 6 Total volume [height  width  length  number of boxes] 1 125 125 Surface-to-volume (S-to-V) ratio [surface area ÷ volume] 6 1.2 6 Does size matter? Fig. 6-8

20. Fimbriae Nucleoid Ribosomes Plasma membrane Cell wall Bacterial chromosome Capsule 0.5 µm Flagella (a) A typical rod-shaped bacterium (b) A thin section through the bacterium Bacillus coagulans (TEM) Features of Prokaryotic Cells Fig. 6-6

21. Organisms with eukaryotic cells • Animals • Plants • Fungi • Protists

22. Figure 6.8a ENDOPLASMIC RETICULUM (ER) Nuclearenvelope SmoothER RoughER Flagellum NUCLEUS Nucleolus Chromatin Centrosome Plasmamembrane CYTOSKELETON: Animal Cell Microfilaments Intermediate filaments Microtubules Ribosomes Microvilli Golgi apparatus Peroxisome Lysosome Mitochondrion

23. Figure 6.8c Nuclearenvelope Roughendoplasmicreticulum Smoothendoplasmicreticulum NUCLEUS Nucleolus Chromatin Ribosomes Central vacuole Golgiapparatus Microfilaments Plant Cell Intermediatefilaments CYTOSKELETON Microtubules Mitochondrion Peroxisome Chloroplast Plasma membrane Cell wall Plasmodesmata Wall of adjacent cell

24. Features Found in Plant Cells, but NOT Animal Cells • Cell Wall • Chloroplast • Central vacuole • Plasmodesmata

25. Features Found in Animal Cells, but NOT Plant Cells • Lysosomes • Centrosomes • Flagella

26. Nucleus 1 µm Nucleolus Chromatin Nuclear envelope: Inner membrane Outer membrane Nuclear pore Pore complex Rough ER Surface of nuclear envelope Ribosome 1 µm 0.25 µm Close-up of nuclear envelope Pore complexes (TEM) Nuclear lamina (TEM) Fig. 6-10 Nucleus

27. Cytosol Endoplasmic reticulum (ER) Free ribosomes Bound ribosomes Large subunit Small subunit 0.5 µm Diagram of a ribosome TEM showing ER and ribosomes Fig. 6-11 Ribosome

28. Transport vesicle from Golgi to plasma membrane Transport vesicle from ER to Golgi Rough ER Plasma membrane Nucleus Vacuole Lysosome Nuclear envelope Golgi apparatus Smooth ER Endomembrane System: Overview

29. Smooth ER Nuclear envelope Rough ER ER lumen Cisternae Transitional ER Ribosomes Transport vesicle 200 nm Rough ER Smooth ER Endoplasmic Reticulum (ER) Fig. 6-12

30. Smooth ER • Three functions of the Smooth ER: • Lipid production • Detoxifying enzymes • Calcium ion storage

31. Rough ER • Two functions of the Rough ER: • Membrane production • Along with ribosomes, produce proteins for use within the endomembrane system or for secretion from the cell • Protein modification

32. Transport vesicle buds off Secretary (glyco-) protein inside trans- port vesicle Ribosome Sugar chain Glycoprotein Polypeptide Rough ER

33. Golgi Apparatus (Golgi Complex) cis face(“receiving” side ofGolgi apparatus) 0.1 m Cisternae Figure 6.12 trans face(“shipping” side ofGolgi apparatus) TEM of Golgi apparatus

34. Lysosome Vesicle containingtwo damagedorganelles 1 m Nucleus 1 m Figure 6.13 Mitochondrionfragment Peroxisomefragment Lysosome Digestiveenzymes Lysosome Lysosome Peroxisome Plasma membrane Digestion Food vacuole Digestion Mitochondrion Vesicle (b) Autophagy (a) Phagocytosis

35. Central vacuole Cytosol Figure 6.14 Central Vacuole Centralvacuole Nucleus Cell wall Chloroplast 5 m

36. Nucleus Figure 6.15-1 Rough ER Smooth ER Plasmamembrane

37. Nucleus Figure 6.15-2 Rough ER Smooth ER cis Golgi Plasmamembrane trans Golgi

38. Nucleus Figure 6.15-3 Rough ER Smooth ER cis Golgi Plasmamembrane trans Golgi

39. Mitochondria: Powerhouse of the Cell • Mitochondria are divided into two compartments (separated by the innermembrane): • Intermembrane space • Mitochondrial matrix

40. Endoplasmicreticulum Nucleus Engulfing of oxygen-using nonphotosyntheticprokaryote, whichbecomes a mitochondrion Nuclear envelope Figure 6.16 Ancestor ofeukaryotic cells(host cell) Mitochondrion Engulfing ofphotosyntheticprokaryote At leastone cell Chloroplast Nonphotosyntheticeukaryote Mitochondrion Photosynthetic eukaryote

41. Mitochondria: Powerhouse of the Cell 10 m Intermembrane space Figure 6.17 Mitochondria Outer membrane DNA Inner MitochondrialDNA Freeribosomesin themitochondrialmatrix membrane Cristae Nuclear DNA Matrix 0.1 m Network of mitochondria in a protistcell (LM) (b) (a) Diagram and TEM of mitochondrion

42. Chloroplasts: Site of Photosynthesis • Converts solar energy into chemical energy • Chloroplasts are divided into three compartments: • Intermembrane space • Stroma • Grana

43. Chloroplasts: Site of Photosynthesis Figure 6.18 50 m Ribosomes Stroma Inner and outer membranes Granum Chloroplasts(red) DNA Intermembrane space 1 m Thylakoid (b) Chloroplasts in an algal cell (a) Diagram and TEM of chloroplast

44. Peroxisome 1 m Chloroplast Peroxisome Figure 6.19 Mitochondrion

45. Cytoskeleton • Microfilaments – thinnest • Intermediate filaments • Microtubules – thickest

46. Cytoskeleton Figure 6.20 10 m • Microfilaments – thinnest • Intermediate filaments • Microtubules – thickest

47. Table 6.1 5 m 10 m 10 m Column of tubulin dimers Keratin proteins Actin subunit Fibrous subunit (keratinscoiled together) 25 nm 812 nm 7 nm Tubulin dimer  

48. Direction of swimming Figure 6.23 (a) Motion of flagella 5 m Cilia and Flagella Direction of organism’s movement Power stroke Recovery stroke (b) Motion of cilia 15 m

49. Outer microtubule doublet Plasma membrane 0.1 µm Dynein proteins Central microtubule Radial spoke Protein cross-linking outer doublets Microtubules Fig. 6-24 (b) Cross section of cilium Plasma membrane Basal body 0.5 µm 0.1 µm (a) Longitudinal section of cilium Triplet (c) Cross section of basal body

50. Secondary cell wall Primary cell wall Middle lamella Fig. 6-28 1 µm Central vacuole Cytosol Plasma membrane Plant cell walls Plasmodesmata