Cellular Organization

1. Cellular Organization

2. Characteristics of life All organisms (uni- & multicellular) carry out the same functions of life: 1) All life is made of cells. 2) Reproduction: life comes from life (biogenesis). 3) Heredity directed by DNA: growth & development. 4) Metabolism: energy utilization and transformation. 5) Homeostasis: maintenance of steady-state conditions. 6) Response to stimuli: organisms sense and react to their environment. 7) Evolutionary adaptation: life changes in response to interactions between organisms and environment.

3. Cell theory Robert Hooke first described cells in 1665 using a microscope he made himself.

4. Cell theory The cell theory has developed since Robert Hooke’s work beginning in 1665. There are three components: • All organisms are composed of one or more cells; • Cells are the smallest units of life; • All cells come from pre-existing cells.

5. Evidence for the cell theory 1) All organisms are com- posed of one or more cells: • Hooke’s observations of cork cells in 1665: Hooke coined the term “cell”, since the com- partments reminded him of the rooms (or cells) of monks.

6. Evidence for the cell theory 1) All organisms are composed of one or more cells: • Antonie van Leeuwenhoek observed the first living cells (the alga Spirogyra) in the 1670s.

7. Evidence for the cell theory 1) All organisms are composed of one or more cells: • In 1838 Mathias Schleiden observed that plants are made of cells.

8. Evidence for the cell theory 1) All organisms are composed of one or more cells: • In 1839 Theodor Schwann observed that animals are made of cells. http://www.youtube.com/watch?v=dscY_2QQbKU

9. Evidence for the cell theory 2) Cells are the smallest units of life: • To date, no one has found a living thing on Earth that is not made of at least one cell. • But viruses are not made of cells. Are they alive? Bacteriophages infecting a bacterium

10. Evidence for the cell theory 3) All cells come from pre-existing cells. Spontaneous generation is the idea that life can be generated from non-living matter. • The concept goes back to Aristotle ~330 BC; if meat were left out, maggots would appear in a few days. • Francesco Redi disproved this in 1668. Maggot eggs seen on cloth

11. The size of cells and other things Although cells can be seen with a light microscope, viruses are too small to be seen that way. • The electron microscope bounces electrons off targets, so smaller things can be seen.

12. The size of things The electron microscope

13. The size of things The electron microscope shows the relative sizes of molecules, cell membrane thickness, and viruses. Molecules from 1 nm Membranes about 10 nm

14. The size of things Viruses: up to 100 nm Bacteriophage HIV budding from infected cell Tobacco mosaic virus

15. The size of things But cells and most organelles can be seen with the light microscope. • Cells are up to 100 μm (100 micrometers). • Organelles up to 10 μm. Chloroplast

16. Calculating magnification Images must contain a scale bar to indicate size. • Scale is indicated on photo or in text. • Multiply to find the actual size of material. From text, bar = 1 micron, so width of strand = 2 x 1 = 2μm. Photo states bar = 20 nm, so length of molecule = 8 x 20 = 160 nm.

17. The size of life A comparison of sizes • http://www.cellsalive.com/howbig.htm

18. Limits to cell size Why are cells so small? • As a cell increases in size, volume increases faster than surface area. Smal- ler cells have a greater ratio of surface area/volume . Cube a Cube b Cube c

19. Emergent properties of multicellular organisms New properties emerge in multicelled organisms. • Differentiation allows for specialization of cells. • for digestion, reproduction, sensing the environment, etc.

20. Cell differentiation Multicellular organisms differentiate to carry out specialized func- tions by expressing some of their genes but not others. *After birth many genes are “turned off” permanently. *Think how puberty causes new developments to occur that were not there previously - other DNA is “turned on”.

21. Cell differentiation Some cells retain the capacity to divide, as well as their ability to differentiate. • Example: cuttings from plants produce whole plants.

22. Stem cells Stem cells retain the capacity to divide and have the ability to differentiate along different pathways. • One type (em- bryonic stem cells) must be harvested from aborted embryos.

23. Stem cells • Adult (somatic) stem cells are unspecialized cells that are found in different parts of the body (like bone marrow). • Umbilical cord blood from newborns also has a potential for the harvesting of stem cells.

24. Stem cells • Therapeutic uses of stem cells:

25. Cellular Organization Prokaryotes

26. Objectives • 2.2.1 – Draw & label a diagram of Escherichia coli (E. coli) as an example of a prokaryote. • 2.2.2 – Annotate the diagram from 2.2.1 with the functions of each named structure. • 2.2.3 – Identify structures from 2.2.1 in electron micrographs of E. coli. • 2.2.4 – State that prokaryotes divide by binary fission.

27. Prokaryotic cells Prokaryotes are in the kingdoms Archaebacteria and Eubacteria. • Unicellular bacteria. • No membrane-bound organelles. • DNA is not separated from cytoplasm (no nucleus). • Usually very small in size (~1 μm). (Bacteria on a pinhead)

28. Prokaryotic cells An example of a prokaryote is Escherichia coli (E. coli), a symbiotic bacterium that lives in the human gut and helps us digest our food. • Draw & label: • No nucleus orother organelle

29. Escherichia coli Functions of bacterial structures • Nucleoid (or chromosome): the structure of DNA that contains the heredity of the bacterial life.

30. Escherichia coli Functions of bacterial structures • Ribosomes: granules of RNA that translate the original DNA code into protein.

31. Escherichia coli Functions of bacterial structures • Plasma membrane: a lipid bilayer with proteins re- sponsible for transport of ions, nutrients & waste.

32. Escherichia coli Functions of bacterial structures • Cell wall: A barrier of sugars and proteins (peptido- glycan) that produces the shape of the bacterium. • 2 types – Gram pos. (purple) Gram neg. (pink)

33. Escherichia coli The Gram stain is a way to partially identify bacteria based upon their cell wall characteristics. • E. coli are gram negative bacilli (left below). Gram negative Gram positive

34. Prokaryotic cells Shapes of bacteria: • coccus (2 cocci) – round • bacillus (2 bacilli) – rod • spirillum (2 spirilla) - spiral Staphylo- = grape Strepto- = chain Diplo- = pair

35. Prokaryotic cells Electron micrographs of E. coli show more detail than is possible with a light micro- scope.

36. Prokaryotic cell division Prokaryotes divide by binary fission. • The cell grows, DNA is copied, then it splits into 2 daughter cells.

37. Cellular Organization Eukaryotes

38. Objectives • 2.3.1 – Draw and label a diagram of the ultra- structure of a liver cell as an example of an animal cell. • 2.3.2 – Annotate the diagram from 2.3.1 with the functions of each named structure. • 2.3.3 – Identify structures from 2.3.1 in electron micrographs of liver cells.

39. Eukaryotic cells Eukaryotes are found in the kingdoms Protista, Fungi, Plantae, and Animalia. • Cells are subdivided by internal membranes into compartments called organelles. • The DNA is segregated inside a nucleus. • They are ~1000 times bigger than prokaryotes.

40. Unicelluler eukaryotes (protists) Single cells and colonies Giardia (l) & Trichomonas Diatoms (l) & Volvox

41. Multicellular eukaryotes Top left – human cheek cells Top right – fungal cells Bottom – plant cells

42. Eukaryotic cells Unlike prokaryotes, eukaryotes have a nucleus and other organelles. All cells have: cell membrane, cytoplasm, & ribosomes.

43. Eukaryotic cells A comparison of animal cells and plant cells Animal cell Plant cell (Things in magenta are unique to that type of cell.)

44. Eukaryotic cell The cell membrane separates a living cell from its nonliving surroundings. • A mosaic of proteins in two layers of fatty material. • 8 nm thick; controls traffic into and out of the cell. • Selectively permeable: only certain substances pass.

45. Eukaryotic cells The cytoplasm is everything inside the cell membrane • The cytosol is the watery solution alone. Cytoplasm

46. Eukaryotic cell The nucleus contains most of the genes in a eukaryotic cell (some are located in mitochondria and chloroplasts). • Control center for the cell. • The nucleolus man- ufactures parts to make ribosomes. • Nuclear pores allow materials to exit.

47. Eukaryotic cells Ribosomes build a cell’s proteins. • Ribosomes are made of RNA and protein. • Cells that make more proteins have more ribosomes.

48. Eukaryotic cells Ribosomesbuild a cell’s proteins. • Proteins form as the ribosome translates a piece of messenger RNA.

49. Eukaryotic cells The endoplasmic reticulum manufactures membranes and performs many other biosynthetic functions. • Continuous with the nuclear envelope. Two regions: • Smooth ER lacksribo- somes; rich in enzymes that synthesize lipids. • Rough ER hasribosomes attached to the outside. • abundant in cells that secrete proteins.

50. Eukaryotic cells The Golgi apparatus finishes, sorts, and ships cell products. • Many vesicles from the ER travel to the Golgi apparatus for modifica- tion of their contents. • The Golgi is a center of manufacturing, ware- housing, sorting, and shipping. • The Golgi apparatus is extensive in cells spe- cialized for secretion.