2OverviewPlay key role in synthesis (& hydrolysis) of macromolecules in cellVarious “players” modify macromolecules for various functions
3Endoplasmic Reticulum Functionmanufactures membranes & performs many bio-synthesis functionsStructuremembrane connected to nuclear envelope & extends throughout cellaccounts for 50% membranes in eukaryotic cellrough ER = bound ribosomessmooth ER = no ribosomes
5Smooth ER function Factory processing operations many metabolic processessynthesis & hydrolysisenzymes of smooth ER…synthesize lipids, oils, phospholipids, steroids & sex hormoneshydrolysis (breakdown) of glycogen (in liver) into glucosedetoxify drugs & poisons (in liver)ex. alcohol & barbiturates
6which cells have a lot of rough ER? Rough ER functionProduce proteins for export out of cellprotein secreting cellspackaged into transport vesicles for exportwhich cells have a lot of rough ER?Which cells have a lot of ER?protein production cells like pancreas = production of digestive enzymes (rough endoplasmic reticulum from a cell of exocrine pancreas (88000X))
7Membrane Factory Synthesize membrane phospholipids build new membraneas ER membrane expands, bud off & transfer to other parts of cell that need membranesSynthesize membrane proteinsmembrane bound proteins synthesized directly into membraneprocessing to make glycoproteinsPortion of a hepatocyte showing extensive smooth endoplasmic reticulum (sER) with associated glycogen granules (dark particles). Within the mitochondria are numerous identifiable cristae.
10which cells have a lot of Golgi? Golgi ApparatusFunctionfinishes, sorts, & ships cell products“shipping & receiving department”center of manufacturing, warehousing, sorting & shippingextensive in cells specialized for secretionCells specialized for secretion?endocrine glands: produce hormonespituitary, pancreas, adrenal, testes, ovariesexocrine glands: produce digestive enzymes& other productspancreas, mammary glands, sweat glandswhich cells have a lot of Golgi?
11Golgi Apparatus Structure flattened membranous sacs = cisternae look like stack of pita bread2 sides = 2 functionscis = receives material by fusing with vesicles = “receiving”trans buds off vesicles that travel to other sites = “shipping” (transport)cistrans
14Golgi processingDuring path from cis to trans, products from ER are modified into final formtags, sorts, & packages materials into transport vesiclesGolgi = “UPS headquarters”Transport vesicles = “UPS trucks”delivering packages that have been tagged with their own barcodes
15“Let’s go to the video tape!” Putting it together…“Let’s go to the video tape!”(play movie here)
18LysosomesStructuremembrane-bounded sac of hydrolytic enzymes that digests macromoleculesenzymes & membrane of lysosomes are synthesized by rough ER & transferred to the Golgionly inanimal cells
19Lysosomes 1960 | 1974 Function a little “stomach” for the cell lyso– = breaking things apart–some = bodyalso the “clean up crew” of the cellLysosomes were discovered quite recently, in 1960s, by Christian de Duve. This discovery was so important that he was awarded the 1974 Nobel prize.Why was this discovery so important?1974 Nobel prize: Christian de DuveLysosomes discovery in 1960s
20Cellular digestion Lysosomes fuse with food vacuoles Polymers are digested into monomerspass to cytosol to become nutrients of cell
21Lysosomal enzymes Lysosomal enzymes work best at pH 5 organelle creates custom pHhow?proteins in lysosomal membrane pump H+ ions from the cytosol into lysosomewhy?enzymes are very sensitive to pHenzymes are proteins — pH affects structurewhy evolve digestive enzymes which function at pH different from cytosol?digestive enzymes won’t function well if leak into cytosol = don’t want to digest yourself!lysosomes create a space where cell can digest macromolecules safelyrupturing a few lysosomes has little impact on a cell (pH of cytosol affects functionality of the lysosomal enzymes), but massive leakage from lysosomes can destroy cellwhy evolve digestive enzymes which function at pH so different from cytosol?digestive enzymes won’t function well if leak into cytosol = most times don’t want to digest yourself!low pH = acid environment cause oxidation (removing electrons) & promotes hydrolysis
22When things go wrong…Tay-SachsWhat if a lysomome digestive enzyme doesn’t function?don’t digest a biomoleculeinstead biomolecule collects in lysosomeslysosomes fill up with undigested materiallysosomes grow larger & largereventually disrupt cell & organ function“Lysosomal storage diseases” are usually fatalTay-Sachs diseaselipids build up in brain cellschild dies before age 5
23Where old proteins go to die! “Let’s go to the video tape!” The Recycler“Let’s go to the video tape!”(play movie here)Fuse with organelles or macromolecules in cytosol to recycle materials
25Sometimes its supposed to work that way… Apoptosis = cell deathcritical role in programmed destruction of cells in multicellular organismsauto-destruct mechanism“cell suicide”some cells have to die in an organized fashion, especially during developmentex: development of space between your fingers during embryonic developmentex: if cell grows improperly this self-destruct mechanism is triggered to remove damaged cellcancer over-rides this to enable tumor growthFeedback mechanismThere are sensors in the cell that monitor growth. They trigger self-destruct when they sense processes gone awry.Brown spots on leaves too.Virus infected plant cell auto-destructs and even kills cells around it to wall off virus.
28Peroxisomes Other digestive enzyme sacs in both animals & plants breakdown fatty acids to sugarseasier to transport & use as energy sourcedetoxify celldetoxifies alcohol & other poisonsproduce peroxide (H2O2)must breakdown H2O2 H2O
29“Let’s go to the video tape!” Vacuoles & vesiclesFunctionlittle “transfer ships”Food vacuolesphagocytosis, fuse with lysosomesContractile vacuolesin freshwater protists, pump excess H2O out of cellCentral vacuolesin many mature plant cells“Let’s go to the video tape!”(play movie here)
30Vacuoles in plants Functions storage stockpiling proteins or inorganic ionsdepositing metabolic byproductsstoring pigmentsstoring defensive compounds against herbivoresselective membranecontrol what comes in or goes out