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  1. 7. Basic Characteristics of Cells 1. Basic unit of life-- all life (we know of) depends on cells 2. Cell functions are based entirely on chemical principles interconnected chemical reactions allow cells to function 3. Cells take in more energy than they produce-- thermodynamics 4. Cells specialize to optimize their functions for particular purposes
  2. 8. How large are cells? Few microns
  3. 9. How big is a micrometer (micron)? 1 micron = 1x10 -6 meters 10 -3 10 -2 10 -1 common metric prefixes: kilo- = 10 3 centi- = 10 -2 milli- = 10 -3 micro- = 10 -6 nano- = 10 -9 Angstrom = .10 nm = 1x10 -10 m light microscopes resolve to ~ 0.2 microns electron microscopes resolve to ~ 2 nanometers
  4. 10. Average animal cell about 20 microns in diameter
  5. 11. Up to 1 mm (or more) in diameter, meters long!
  6. 12. Major classifications of cells-- Prokaryotic and Eukaryotic Prokaryote Eukaryote Eukaryotes: are generally larger + complex Membrane bound nucleus Membranes segregate function Endocytosis and exocytosis More organized DNA Meiosis+ sexual reproduction Expression of DNA Have internal cytoskeleton
  7. 13. Organelles
  8. 14. Cell Membrane Lipid bilayer with polar heads and hydrophobic interior found in prokaryotes and eukaryotes forms the limiting boundary of the cell
  9. 15. Cell Membrane semi-permeable membrane-- gasses pass through it, water + ions can't proteins in the membrane transport specific molecules in or out of the cell many sugar groups (carbohydrates) are attached to the proteins and lipids
  10. 16. Nucleus "brain" of the cell-- holds the information stored as DNA and controls cell functions Has it's own lipid bilayer with special "nuclear pores" regulating in and out movement Place where RNA is synthesized and processed
  11. 17. Nucleus DNA is bound to histone proteins in cell-- complex called a chromosome diploid-- 2 copies of each homologous (very similar) chromatid each chromatid duplicates and separates during cell division
  12. 18. Nuclei divide first, followed by rest of the cell
  13. 19. Bacteria have to divide too reproduce by fission-- divide in half -- not as organized as eukaryotes
  14. 20. cytoplasm-- material outside the nucleus inside the cell membrane Cytoskeleton -- "bones" of a cell-- provides structure and support also can act as a highway-- move product from one place to another
  15. 21. Three major fibers form the cytoskeleton: microfilaments - made up of actin form the cleavage furrow during division contractile fibers of muscles smallest fiber - 5-6 nm wide fibers have polarity grow on one end, disassemble on other intermediate filaments middle size - ~10 nm wide most stable-- change less frequently common at sites of mechanical stress diagnostic tool in medicine- tissue specific Cytoskeleton
  16. 22. ~ 10 nm Cytoskeleton
  17. 23. Cytoskeleton Microtubules - largest of the fiber classes (~ 25 nm wide) made up of 2 protein subunits--  and  tubulin like actin, microtubules are polarized with a + and - end provides a 'superhighway' in the cell to move in a direction
  18. 24. Cytoskeleton microtubules make up the spindle fibers that separate chromosomes as well as the flagella that allow motility for many cells
  19. 25. Centrosome microtubule organizing center 2, generally on opposite sides of nucleus not found in plant cells organizes the spindles during mitosis also important for flagellar organization
  20. 26. Ribosomes found in both prokaryotes and eukaryotes location of protein synthesis complex of proteins and structural RNAs most numerous organelle in cells relatively small organelles-- prokaryotes: 25 nm 70S 30S and 50S subunits eukaryotes: 30nm 80S 40S and 60S subunits
  21. 27. Sedimentation Coefficient Centrifugation is a way of separating substances by density dense things settle to the bottom lighter things stay toward top centrifuges measured by G forces RCF = 1.12r (RPM/1000) 2 (r=radius in mm) sedimentation coefficient is how rapidly a particle moves to the bottom of a centrifuge measured in Svedberg units (S) very useful for separating soluble and insoluble materials as well repeatedly spinning at different speeds can generate multiple fractions
  22. 28. Endoplasmic Reticulum (ER) ER is a series of folded membranes within a cell smooth ER is site of most membrane synthesis rough ER looks spotted due to ribosomes bound on the surface rough ER is location of membrane, secreted or otherwise targetted protein synthesis eukaryotes only
  23. 30. Endoplasmic Reticulum (ER) ER is continuous with the nuclear membrane amount of ER varies by cellular function liver cells have lots of ER- used to detoxify chemicals cells optimized for protein secretion have lots of rough ER
  24. 31. Golgi Complex Series of flattened membranes that processes proteins, primarily glycosylation (adding carbohydrates) vessicles carry proteins from one stack to another, and eventually to their final destination receives proteins to be glycosylated from the endoplasmic reticulum
  25. 32. Vacuole extremely large and prominent in plant cells smaller and more numerous in animal cells in animal cells, primarily storage granules in plants, performs storage, some digestive functions, but primarily regulates turgor pressure turgor pressure supplies rigidity
  26. 33. Lysosome 'digestive' organelle-- breaks down storage molecules, endocytosed material, or cellular material that is no longer needed needs to be isolated to prevent breaking down rest of the cell! digested particles are released into the cytoplasm where they are recycled
  27. 34. Peroxisome both generates and degrades hydrogen peroxide detoxifies certain chemicals and converts some substances breaks down long chain fatty acids also has a role in photorespiration first isolated as a biochemical fraction
  28. 35. Cell Wall primary cell wall generally contains cellulose and other polysaccharides secondary cell wall, if present, is more rigid and contains lignin and higher cellulose content plasmodesmata are cytoplasmic links between plant cells passing through cell walls Bacterial cell walls contain peptidoglycans instead of cellulose
  29. 36. Extracellular Matrix Secreted by animal cells, not plants contains mostly collagen and proteoglycans elastic network allowing freedom of movement and not cell wall rigidity aids in support and recognition events basal lamina - extracellular matrix around muscle cells- important in muscle cell function and synapse formation
  30. 37. Mitochondria Found in both plants and animals about the size of a bacteria 2 membranes, inner and outer cristae -- folds of the inner mitochondrial membrane matrix -- semiliquid material between cristae oxidizes sugars and other foods for energy primary site for the generation of adenosine triphosphate, the main energy transfer unit of the cell
  31. 38. Chloroplast only found in plants huge-- 5-10 microns long have inner, outer, and thylakoid membranes thylakoid -- flattened membrane sack grana -- stacks of thylakoids chloroplasts are sites of photosynthesis, with carbon fixation taking place within the stroma also use nitrates from soil to make ammonia (NH 4 ) for amino acids stroma thylakoid } granum
  32. 39. Chloroplasts and Mitochondria both have own circular DNA, ribosomes, tRNAs, and internal membranes ribosomes are more similar to prokaryotic than eukaryotic in size/function both membrane bound and involved in energy production/utilization overall size is similar to prokaryotes (about 2 micron in length)
  33. 40. Endosymbiont Theory suggests that an early one cell organism, protoeukaryotes, developed a sybiotic relationship with a primative bacteria and cyanobacteria phagocytosis -- property of surrounding something (perhaps a nutrient) within a membrane and pinching it off so it becomes enclosed algae, diatoms, and others live symbiotically with at least 150 known species of invertebrates and protists, some have even lost their cell walls even though the earliest life forms are not available for observations, we can still find evidence for some of their characteristics today
  34. 41. Viruses Obligate cellular parasites-- can't replicate without cells nucleic acid core (DNA or RNA) surrounded by a protein coat take over cellular machinery to reproduce themselves and eventually kill the host cell
  35. 42. Viruses Many viruses cause disease Ebola virus Smallpox virus HIV virus
  36. 43. Viruses bacteriophage are viruses that infect bacteria vital to early molecular biology Tobacco mosaic virus infects plants excellent model for studying life cycle viruses can be used for genetic engineering of plants and animals