Cells & Organelles

1. Cells & Organelles A Dr. Production

2. Two Basic Types of Cells • Prokaryotes: • prounounced: pro-carry-oats • Eu karyotes • Proun: you-carry-oats Organization of Domains Evolution of the 3 Domains

3. Development of the Cell Theory • Hooke (1665) named the cell • Schwann (1800’s) states: -all animals are made of cells • Pasteur (1859) disproved idea of spontaneous generation • living things arise from nonliving matter • Modern cell theory emerged • -All organisms composed of cells and cell products. • -Cell is the simplest structural and functional unit of life. • -Organism’s structure and functions are due to the activities of its cells. • -Cells come only from preexisting cells. • -Cells of all species have many fundamental similarities.

4. A. Prokaryotes • Small, simple cells (relative to eukaryotes) • Size: about 1 µm (1 micron) • No internal membrane-bounded organelles • No nucleus • Simple cell division • Single linear chromosome Contain the domains; 1. True (Eu)bacteria & 2. Archaebacteria

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

6. Eubacteria • Peptidoglycan cell walls (carbos & AA) • Separated into Gram + and - forms

8.  Gram positive Gram negative

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

10. Archaea = Extremophiles 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.

11. 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).

12. 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

13. Eukaryotes • Larger more complex cells that make up most familiar life forms: plants, animals, fungi, protists • Surrounded by a cell membrane made of lipids

14. Cell Size • Human cell size • most from 10 - 15 µm in diameter • egg cells (very large)100 µm diameter • nerve cell (very long) at 1 meter long • Limitations on cell size • cell growth increases volume faster than surface area • nutrient absorption and waste removal utilize surface

15. 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 • Cell surface area is important in taking in nutrients • Surface 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

16. Cell Surface Area and Volume Why can’t cells be infinitely large?

17. Cell Shape and Function

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

19. 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…

20. 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 & proteinin the form of chromatin

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

22. 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..

23. Plastids Synthesize carbohydrates • Leucoplasts: white in roots and tubers • Chromoplasts: rainbow accessory pigments • Chloroplasts: green in leaves and stems

24. Chloroplasts • Found in plants and some protists. Responsible for capturing sunlight and converting it to food = photosynthesis. • Surrounded by 2 membranes • And…contain DNA

25. Ribosomes • Size ~20nm • Made of two subunits (large and small) • Composed of RNA and over 30 proteins • Come in two sizes…80S (40s + 60s) and 70S (30s + 50s) • S units = Sedimentation speed

26. 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.

27. Endoplasmic Reticulum = ER • Cytoplasm is packed w. membrane system which move molecules about the cell and to outside • Outer surface of ER may be smooth (SER): synthesizes secretes, stores, carbs, lipids and non pps • Or Rough (RER): synthesizes pp for secretion • ER functions in lipid and protein synthesis and transport

28. 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

29. ER to Golgi network/ Endomembrane system

30. Membrane Flow through Golgi

31. 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 apoptosis

32. Vacuoles • Formed by the pinching of the cell membrane • Very little or no inner structure • Stores various items

33. Peroxisomes/Microbodies • Large vesicles containing oxidative enzymes which transfer H from substrates to O • Contains catalase that changes H2O2 to H2O • In plants responsible for photorespiration and converting fat to sugar during germination

34. Cytoskeleton • Composed of 3 filamentous proteins: Microtubules Microfilaments Intermediate filaments • All produce a complex network of structural fibers within cell 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.

35. Microtubules Function in: • Involved in cell shape, mitosis (spindle fibers), flagellar movement, organelle movement (“transport” system within cell) • Long, rigid, hollow tubes ~25nm wide • Composed of a and ß tubulin (small globular proteins) • 9+2 vs 9x3 arrangement

36. 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

37. Flagella (flagellum) • Motile structure of many eukaryotic cells; long, hair-like projection - e.g., tail of sperm • Core composed of 9 + 2 array of microtubules that arise from a basal body apparatus • Flagellated E. coli

38. Cilia (cilium) • Motile or sensory structure in eukaryotes composed of 9 + 2 array of microtubules • Usually numerous short, hair-like projections along outside of cell • Found in many Protista and in lining of lungs • Stentor feeding • Paramecium rotating

39. 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)

40. 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 Image of Lamins which reside in the nucleus just under the nuclear envelope

41. Possible Origins of Eukaryotic Cells

42. Support for this Theory: • Eg. of this type of symbiosis are found today. Sponges harbor photosyn. algae within their tissues, allowing them to photosynthesize. • The organelles (chloroplasts and mitochondria) resemble bacteria in size and structure. • These organelles each contain a small amount of DNA but lack a nuclear membrane. • Each has the capability of self-replication. They reproduce by binary fission. • They make their own proteins. • During protein synthesis, these organelles use the same control codes and initial amino acid as prokaryotes. • They contain and make their own ribosomes, which resemble prokaryote’s. • The enzymes that replicate DNA and RNA (polymerases) of the organelles are similar to those in prokaryotes but different from those of eukaryotes.  • The organelles have a double membrane that might be derived from a prokaryote’s plasma membrane and the membrane of a vesicle.

43. Resources • Rediscovering Biology Animation Guide • Cell Signaling and Cell Cycle Animations • Molecular Movies • Apoptosis Animation • Bacterial Animations