“Five kingdom system:” Divide all organisms into groups (kingdoms)--different groups have different combinations of cell parts (organelles) ! Procaryota ! Animalia ! Plantae ! Fungi ! Protista
Classification of organisms
Classification by molecular biology
Modern systems divide organisms into groups-- (domains, kingdoms)—on the basis of DNA sequences
Plasma Membrane
Thin sheet 7-9 nm (0.007-0.009 !m) thick Composition: lipid (fat) and protein Found in all cells Functions: ! serves as platform for biochemical reactions ! recognizes outside stimuli ! controls transport of molecules (and larger things) into and out of cell.
Cell Wall
Thick net (variable width) surrounding the plasmamembrane; rigid
Found in most prokaryotes (bacteria, archaea); alsoplants, fungi, some protists
Composition: peptidoglycan, cellulose, chitin, etc.(long molecules, porous net)
Functions! limits the size of cell! controls cell growth
Nucleoid
Nucleic acid (long, stringy molecule) in center of cell
Function: contains information (DNA)! cell functions (metabolism)! growth of cell! reproduction
Ribosomes
Small, solid spheroids (0.02 !m diameter) Nucleic acid (RNA) and protein, two subunits each Ave. 30,000 per cell Function ! synthesis of proteins
Eukaryotes
! Plants, Animals, Fungi, Protists ! Complex cell structures ! Multicellular organisms, with specialized cells
Organelles in prokaryotes that are the"same" in eukaryotes
Plasma membrane
Cell wall (in plants, fungi, some protists)
Ribosomes
Nucleus (nuclei)
Spheroid, 10-20 !m diameter
Present in all eukaryotes: usuallyone per cell (more? coenocytic orsyncitial)
Surrounded by nuclear envelope
Nucleolus: makes ribosomes
Chromatin:! Nucleosomes! Chromosomes! Centromeres! Telomeres
Function: like nucleoid of prokaryotes
Mitochondrion (-dria)
Spheroid ca. 1 !m diameter Surrounded by a double membrane Crista (-ae): inner membrane folds Matrix: liquid gel center Function: directs energy transformation, metabolism Found in all eukaryotic cells: 1 to 10,000 (ave. 100) per cell
Mitochondria in cornial cells are long and tubular
a and d and green in c and f is autofluorescenceb and e and red in c and f is a fluorescent dye absorbed by mitochondria
Plastid
Spheroid 5 !m diameter Found in plants and some protists ! Double membrane ! Thylakoids ! Stroma Functions depend on type: ! Chloroplast (green) ! Leukoplast (white) ! Chromoplast (colored) ! Proplastids
Organelles in prokaryotes and eukaryotes
! Plasma membrane ! Cell wall (in prokaryotes, plants, fungi, some
protists) ! Ribosomes
! Nucleoid/nucleus
! Mitochondrion
! Plastids
Endoplasmic reticulum (E.R.) (“networkbetween organelles”)
Interconnected flattened or tubular sacs,cisterna(e)
Functions: synthesis and packaging! Rough: proteins! Smooth, cell wall carbohydrates, glycogen
(starch), glycoproteins, steroid hormones.
In all eukaryotic cells
Golgi apparatus (dictyosome, in plants)
Dense complex of cisternae, several per cell
Functions:! synthesis of carbohydrates on proteins
(glycoproteins),! transport of proteins to different compartments
in cell
Found in all eukarotic cells
Vesicles
Small sacs Single membrane Functions: ! storage, isolation ! transport
Vacuoles
Larger sacs Single membrane In protists, storage organs, digestive organs, related to water pumping (contractile vacuole) In plants and fungi, large storage organs salts, sugars, red and blue pigments in flowers, wastes, strange chemicals (poisons)
Cytoskeleton
Microtubules
Stiff helical rods of protein (tubulin); 25 nm diam
Functions:! Structural support (e.g. mammalian nerve cell).! Support for movement (e.g., vesicles, cilia,
flagella, spindles).
Motor proteins:! Kinesin toward + end! Dynein toward - end
Microfilaments
Flexible rods of protein (actin); 7 nm thick
Functions:! Structural support! Support for movement (e.g., muscles,
streaming).
Motor protein:! Myosin
Intermediate filaments
Stiff protein rods, 8-12 nm thick
Function: hold organelles in place
Figure 4. IF-associated proteins provide flexible intracytoplasmic resilience in response to external stresses by reversibly cross-linking IFsto other cytoskeletal and membrane sites. (A through C) BPAG1n/dystonin, a 280-kD linker protein with actin- and neurofilament-bindingdomains, aligns neurofilaments along actin stress fibers when a cultured mammalian cell is triply transfected to express BPAG1n, NF-L,and NF-H. (A) Neurofilament; (B) BPAG1n/dystonin; (C) actin. [Reproduced with permission from Yang et al. (50).] (D) Electronmicrograph of the residual cytoskeleton of a rat embryo fibroblast after dissolution of actin filaments with gelsolin. Linked to 10-nm goldparticles, antibodies against the 500-kD cross-linker protein plectin reveal bridges between microtubules and IFs. Pseudocolored elementsare microtubules (orange), IFs assembled from vimentin (green), plectin (red), and gold particles marking plectin (yellow). (E) Modelsuggesting that plectin mediates linking between IFs, microtubules, actin, myosin, and membrane-bound adhesion sites (focal contacts orplasma membrane components) (51, 53). (Images kindly provided by T.ハSvitkina and G.ハBorisy.)
Dynamic relationships between membranousorganelles
! E.R. formed by outbudding of nuclear envelope
! E.R. produces vesicles: substances producedin E.R. (e.g. proteins, tagged withcarbohydrates; glycoproteins) appear in vesicles
! Golgi accepts materials from E.R.
! Golgi vesicles modify materials (e.g. alteredglycogroups)
! Golgi vesicles can (a) stay as storage vesicles(e.g. lysosomes), (b) fuse with plasmamembrane to secrete their substance, (c) fusewith another membrane (e.g. vacuolarmembrane) to transfer material into anorganelle.
! Secretion vesicles can be “constitutive” or“regulated”—Golgi targets different materialsinto each.
Cells in various organisms
Plants: have all the organelles described for eukaryotes (except some specialized cells)
Fungi: like plant cells in number and type of organelles, but without plastids (also many other biochemical, structural, and behavioral differences)
Animals: no cell wall, no plastids, no large vacuole
Protists: +/- cell wall, pellicle, contractile vacuole
Bacteria, archaea: +/- cell wall, no nucleus, mitochondria, plastids, E.R., Golgi; but cyanobacteria have thylakoids (like inside of plastids)