Cells: Chapt. 4

1. Cells:Chapt. 4

2. Two Basic Types of Cells • Prokaryotes: • prounounced: pro-carry-oats • Eukaryotes • Proun: you-carry-oats

3. A. Prokaryotes Small, simple cells (relative to eukaryotes) Size: about 1 µm (1 micron) No internal membrane-bounded organelles No nucleus Simple cell division Contain the; 1. true bacteria & 2. archaebacteria

4. 1. True Bacteria = Eubacteria • Majority of bacteria • Examples include: E. coli, Lactobacillus (yoghurt), Lyme disease

5. Eubacteria • Peptidoglycan cell walls (carbos & AA) • Separated into Gram + and - forms Text pg. 58

6. Bacteria in the Environment example: Iron utilizing Baceria B A A) An acid hot spring in Yellowstone is rich in iron and sulfur. B) A black smoker chimney in the deep sea emits iron sulfides at very high temperatures (270 to 380 degrees C).

7. 2. Archaebacteria • Live in extreme environments: high salt, high temps • Different cell wall • Very different membrane lipids • Unusual nucleic acid sequence

8. Archaea types: Based on their physiology, Archae can be organized into three types: • Methanogens (prokaryotes that produce methane); • Extreme halophiles (prokaryotes that live at very high concentrations of salt (NaCl); • Extreme (hyper) thermophiles (prokaryotes that live at very high temperatures). All archaea have features that distinguish them from Bacteria (i.e., no murein in cell wall, ether-linked membrane lipids, etc.). And, these prokaryotes exhibit unique structural or biochemical attributes which adapt them to their particular habitats.

9. B. Eukaryotes • Bigger cells: 10-100 µm • True nucleus • Membrane-bounded structures inside. Called organelles • Divide by a complex, well-organized mitotic process Liver Cell 9,400x

10. Eukaryotes • Larger more complex cells that make up most familiar life forms: plants, animals, fungi, algae • Surrounded by a cell membrane made of lipids • Text pg 60-61

11. The Cell Theory • Cells first observed by R. Hooke 1665 • Named for the Monk prayer cells • Cell Theory states that; 1. All life is composed of cells 2. Cells are the basic units of life 3. Cells arise from already existing cells

12. Cells are typically Small Typical cell size • Text pg. 56

13. Why are Cells Small? • Cells must exchange gases & other molecules with environment… • Nutrients in, Wastes out • As size increases, the rate of diffusion exchange slows down…. • This is due to the ratio of surface area to volume

14. Surface Area to Volume • Cell surface area is important in taking in nutrients • Sfc area increases as the square of cell diameter • But… entire cell volume needs to be fed • And, cell volume increases as the cube of cell diameter

15. Consider 2 Cells... 100 µm diameter 10 µm diameter

16. Surface Area to Volume

17. The Eukaryotic Cell: Components • Outer cell membrane composed of lipids and proteins • Cytoplasm: interior region. Composed of water & dissolved chemicals…a gel • Numerous organelles….

18. Organelles • Specialized structures within eukaryotic cells that perform different functions... • Analogous to small plastic bags within a larger plastic bag. • Perform functions such as : • protein production (insulin, lactase…) • Carbohydrates, lipids… • Text pg 60-61

19. Organelles of Note:The Nucleus • Contains the genetic material (DNA), controls protein synthesis. DNA --> RNA --> Protein • Surrounded by a double membrane with pores • Contains the chromosomes = fibers of coiled DNA & protein • Text pg. 62

20. Chromosomes All Chromosomes from a single cell One chromosome Pulled apart A single chromosome Showing the amount of DNA within

21. Mitochondria • Generate cellular energy in the form of ATP molecules • ATP is generated by the systematic breakdown of glucose = cell respiration • Also, surrounded by 2 membrane layers • Contain their own DNA! • A typical liver cell may have 1,700 mitoch. • All your mitoch. come from your mother.. • Text pg. 68

22. Chloroplasts • Found in plants, algae and some bacteria. Responsible for capturing sunlight and converting it to food = photosynthesis. • Surrounded by 2 membranes • And…contain DNA • Text pg. 69

23. Ribosomes • Size ~20nm • Made of two subunits (large and small) • Composed of RNA and over 30 proteins • Come in two sizes…80S and 70S • S units = Sedimentation speed

24. Ribosomes • DNA --> RNA --> Protein • The RNA to Protein step (termed translation) is done on cytoplasmic protein/RNA particles termed ribosomes. • Contain the protein synthesis machinery • Ribosomes bind to RNA and produce protein.

25. Endoplasmic Reticulum = ER • Cytoplasm is packed w. membrane system which move molecules about the cell and to outside • An internal cellular subway system • Outer sfc of ER may be smooth (SER) • Or Rough (RER) • ER functions in lipid and protein synthesis and transport

26. Golgi Complex • Stacks of membranes… • Involved in modifying proteins and lipids into final form… • Adds the sugars to make glyco-proteins and glyco-lipids • Also, makes vesicles to release stuff from cell • Text pg. 66-67

27. ER to Golgi network

28. Lysosomes • important in breaking down bacteria and old cell components • contains many digestive enzymes • The ‘garbage disposal’ or ‘recycling unit’ of a cell • Malfunctioning lysosomes result in some diseases (Tay-Sachs disease) • Or may self-destruct cell such as in asbestosis • Text pg 67

29. Cytoskeleton • Composed of 3 filamentous proteins: Microtubules Microfilaments Intermediate filaments • All produce a complex network of structural fibers within cell • Text pgs. 72-76 The specimen is human lung cell double-stained to expose microtubules and actin microfilaments using a mixture of FITC and rhodamine-phalloidin. Photo taken with an Olympus microscope.

30. Microtubules • Universal in eukaryotes • Involved in cell shape, mitosis, flagellar movement, organelle movement • Long, rigid, hollow tubes ~25nm wide • Composed of a and ß tubulin (small globular proteins) • Text pg. 72 http://www.cytochemistry.net/Cell-biology/

31. Microfilaments • Thin filaments (7nm diam.) made of the globular protein actin. • Actin filaments form a helical structure • Involved in cell movement (contraction, crawling, cell extensions) • Text pg. 72

32. Intermediate filaments • Fibers ~10nm diam. • Very stable, heterogeneous group • Examples: Lamins: hold nucleus shape Keratin: in epithelial cells Vimentin: gives structure to connective tissue Neurofilaments: in nerve cells Text pg. 72 Image of Lamins which reside in the nucleus just under the nuclear envelope

33. Cell Motility:Flagella & Cilia • Both cilia & flagella are constructed the same • In cross section: 9+2 arrangement of microtubules (MT) • MTs slide against each other to produce movement • Text p 74 Human Sperm: TOTO-3 iodide for DNA (blue) and Nile red for membrane lipid (red)

34. How Flagella Move a Cell

35. Possible Origins of Eukaryotic Cells • Text pg 70 Infolding of outer membranes Uptake of prokaryotes

36. Endosymbiosis • Theory that eukaryotic cells arose from an early prokaryote (1) engulfing a second, smaller prokaryote (2) • The internalized #2 was not digested but became a symbiote. • Today’s mitochondria & chloroplasts may have arisen this way • Text pg. 70

37. Evidence for Endosymbiosis • Double membrane around both organelles • Both organelles have their own DNA • Both organelles have smaller (70S) ribosomes… • Both organelles divide by simple fission