CELLS

1. CELLS The Fundamental Units of Life

2. Cell Theory • All organisms are composed of 1 or more cells. • The cell is the basic living unit, providing organization for all organisms. • All cells arise from preexisting cells.

3. Cells Are Small • Most are too small to be seen with the unaided eye…so Microscopes are used. • A Light Microscope uses visible light shone through glass lenses. • A “thin section” of specimen is required. • van Leeuwenhoek

4. Principles of Microscopy • LIGHT • REFRACTION • MAGNIFICATION • RESOLUTION

5. MAGNIFICATION • Image size exceeds real size. • Achieved with convex lenses. • There are limits… …involving the nature of light. • First, you need enough light to penetrate the thin specimen.

6. RESOLUTION • Next, you need light of appropriate wavelength…or RESOLUTION is compromised. • A measure of clarity – of focus. • Minimum distance between two points that allow the points to be distinguishable. • Light microscopy not very useful below 0.2um.

7. RESOLUTION

8. Electron Microscopy • Uses e- rather than light. • Electrons have a much shorter wavelength. • SEM = Scanning Electron Microscopy • TEM = Transmission Electron Microscopy

9. Electron Microscopy

10. Cells!

11. ALL CELLS • Plasma Membrane (Cell Membrane) • Separate the contents of the cell from the environment. • Cytoplasm (Cytosol) • Semi-fluid contents of the cell • Lots of “floaties” • Nucleus “area” • Location of DNA

12. CELLS • Eukaryotic Cells(animals, plants, fungi, protists) • Complex & relatively large. • Membrane-bound nucleus & organelles. • 80-S Ribosomes. • Prokaryotic Cells(archaea, bacteria) • Simple & relatively small. • NO Membrane-bound nucleus & organelles. • 70-S Ribosomes.

13. Prokaryote vs Eukaryote

14. CELLS PROKARYOTICEUKARYOTIC

15. EUKARYOTIC CELLS Organelles = “little organs” (not really) Membrane-bound

16. ORGANELLES • Nucleus • Isolates the DNA & provides access to its hereditary information. • The “control center” of the cell (Transcription).

17. Nucleus • Nuclear Envelope (a double membrane) with Pores. • Nucleolus • rRNA • Proteins • Ribosomes • Nucleoplasm with Chromatin/Chromosomes.

18. Ribosomes • Not true organelles, more “structures”. • Protein factories. • 2 sub-units. • Free (in cytoplasm), more for intracellular activities. • Bound (on E.R.), often for extracellular activities (secretion) & packaging within certain organelles.

19. Endomembrane System • Synthesis of Proteins & their transport into membranes and/or organelles. • Packaging of Proteins for transport out of the cell (secretion) or to other areas of the cell. • Modification of Proteins. • Transport of lipids, lipoproteins, glycoproteins, etc.

20. Endomembrane System • Endoplasmic Reticulum (E.R.) • Rough E.R. • Smooth E.R. • Golgi Apparatus • Vesicles • Lysosomes (also, nuclear envelope, vacuoles, and plasma membrane)

21. Endoplasmic Reticulum • Network of interconnected membranes (continuous with the nuclear envelope). • Flattened or tubular Cisternae.

22. Rough E.R. • The site of protein synthesis, particularly secretory proteins. • Initial modification of proteins. • Especially, formation of Glycoproteins. • Formation (budding) of Transport Vesicles. • Formation of NEW Membrane = Phospholipid Synthesis

23. Smooth E.R. • Modification of Proteins. • Formation of Lipids, detoxification. • Lipid-derived hormones (steroids) are synthesized, including sex hormones (testosterone, etc.) in certain glands. • Solubilization of toxins (drugs, alcohol, caffeine, etc. ) in liver cells.

24. Golgi Apparatus • Modification, storage, sorting, & shipping of ER-produced molecules (esp. for secretion). • Addition of non-protein portions to protein molecules.

25. Golgi Apparatus • Stacks of cisternae, with cis & trans faces. • Cis – receiving (takes in vesicles). • Trans – sending (gives rise to vesicles).

26. Lysosomes • Specific vesicles carrying digestive enzymes – hydrolytic (proteolytic) enzymes. • Animal Cells. • Digestion of food brought in by phagocytosis.

27. Lysosomes • Digestion and recycling of old & damaged organelles within the cell: Autophagy.

28. Endomembrane System

29. Vacuoles • Large vesicles with particular functions. • Food Vacuoles. • Contractile Vacuoles. • Central Vacuole w/ tonoplast in Plant Cells. • Storage. • Dissolved Solutes. • Dumping Ground. • Protection. • Shape.

30. Mitochondrion • Surrounded by a double membrane – an envelope. Outer Membrane Inner membrane (Cristae) Matrix

31. Mitochondrion • Site of cellular respiration = energy production. Carbohydrates ATP • Not part of endomembrane system. • Have their own DNA, RNA, Proteins, and Ribosomes (70-S). • Grow and reproduce independently. • Animals, Plants, Fungi, Protists.

32. Chloroplast • Surrounded by a double membrane – an envelope. Inner Membrane (Grana composed of stacked Thylakoids) Outer Membrane Stroma

33. Chloroplast • Site of Photosynthesis = acquisition of chemical energy from sunlight. Sunlight + CO2 Carbohydrates • A plastid (not part of endomembrane system). • Have their own DNA, RNA, Proteins, and Ribosomes (70-S). • Grow and reproduce independently. • Plants, Protists.

34. Cytoskeleton • Fiber-like structures that lend organization. • Support (providing a scaffolding onto which organelles & vesicles can be organized). • Shape (maintain particular shape depending on the cell’s location and/or function). • Transport of materials around or out of the cell. • Motility of the whole cell from one location to another.

35. Cytoskeleton Microtubules Microfilaments Intermediate Filaments Keratin Subunits Tubulin Actin Keratin

36. Cytoskeleton • Permanent • Flagella • Cilia • Muscle Contraction • Scaffolding & Shape Maintenance

37. Cytoskeleton • Transient • Spindle Fibers • Transport filaments

38. Cell Wall • OUTSIDE the Cell Membrane (technically, outside the cell!) • Various proteins & glycoproteins in Prokaryotes. • Cellulose in Plants. • Chitin in Fungi.

39. Eukaryotic Cell

40. Endosymbiont Theory

41. Onion Cells

42. Membranes Phospholipid Bilayer + Proteins