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Cell Organelles By Diana L. Duckworth Rustburg High School Campbell County Nucleus • Enclosed by nuclear envelope – Double membrane, each a lipid bilayer – Two membranes merge in pores • Protein lined channels for exit of mRNA and ribosomes from nucleus • Within nucleus one or more nucleoli – Site for the manufacture of ribosomes • Chromatin – DNA in combination with proteins – Diffuse mass uncoiled chromatin so DNA can be transcribed; condensed (tightly coiled) during cell division Nucleus Ribosomes Pores Chromatin http://biology.about.com/library/weekly/aa032300a.htm Nucleoli (nucleolus – singular) Nuclear Envelope http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookCELL2.html Endoplasmic Reticulum (ER) • Membrane system within cytoplasm • Connected to nuclear envelope • Two kinds of ER – Smooth endoplasmic reticulum • Synthesis of lipids, phospholipids, steroids • Detoxifies drugs (good & bad) • Stores calcium ions in muscle cells – Rough Endoplasmic Reticulum • Ribosomes attached to ER • Synthesis of proteins and hormones for sectretion Rough Endoplasmic Reticulum http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookCELL2.html Ribosomes – Free or Attached to ER Free manufacture proteins for use in cytoplasm; attached to ER they manufacture proteins for export outside cell. http://biology.about.com/library/weekly/aa033000a.htm Golgi Apparatus • Stack of flattened membranous sacs (cisternae) • Finishing and distribution of export products & does make some polysaccharides for export • Vesicles from ER bud off and merge with one side of Golgi apparatus (near E.R.) • Cisternae mature through the stack • Finished products bud off from other side in transport vesicles Golgi Apparatus http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookglossD.html http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookCELL2.html Formation of Golgi & export of products http://employees.csbsju.edu/hjakubowski/classes/ch331/cho/ergolgi.jpeg Lysosomes • Digestive vesicle produced by Golgi – Acidic environment in lysosome – Contains enzymes that break down macromolecules & recycle components • Function by engulfing material from cytoplasm (autocytosis) or by merging with food vacuoles – Food vacuoles form when cell engulfs something from outside cell (phagocytosis) Vacuoles • Membrane bound sacs serve a variety of purposes • Food vacuoles form when cell engulfs material from outside cell (phagocytosis) • Plant cell vacuoles surrounded by membrane called tonoplast – Used as storage for cell wastes, water – Get larger by merging with smaller vacuoles – Occupy most of volume of plant cell, cytosol is thin region between vacuole & membrane Mitochondria • Site of cellular respiration – Generate ATP from extracting energy from sugars, fats & other fuels • Enclosed by membranes that are not part of cellular membrane system – Has at least 2 membranes separating interior from cytosol – Contain both ribosomes and DNA – Some membrane proteins are imported from cytosol • Grow and reproduce within cell, separate from cellular reproduction Mitochondria http://desertfiddlekate.blogspot.com/2007/06/compendium-reviewone.html http://www.answers.com/topic/mitochondria-1?cat=technology Chloroplasts • Conversion of light energy to chemical energy in sugars • One of group of organelles – plastids • Surrounded by 2 membranes (not ER) • Internal membrane system called thylakoids • Stacked thylakoids called granas • Surrounding fluid called stroma & contains DNA, ribosomes, enzymes http://www.williamsclass.com/Seve nthScienceWork/CellTheoryParts. htm Peroxisomes • Single membrane bound vesicles • Contain enzymes initiate breakdown of complex molecules into smaller molecules – By-product is hydrogen peroxide (toxic) – Enzymes convert this to water • Do NOT form by budding from ER – Grow larger by adding proteins formed in cytosol & lipids made in ER – Split in two when become too large Cytoskeleton – 3 components • Microtubules – largest; hollow rods – – – – function in cell division Mobility of organelles Shape & support cell Responsible for beating of cilia & flagella • Microfilaments (Actin filaments & Myosin filaments) – Resist tensional forces on cell – Contractile apparatus in muscle cells, cell motility • Intermediate filaments – Control shape of cell; more permanent http://www.williamsclass.com/SeventhScienceWork/CellTheoryParts.htm Extracellular Components of Cells • Plant cell walls – Protection; prevents excessive water uptake; maintains shape – Cellulose (polysaccharide) fibrils embedded in matrix of other polysaccharides and proteins • Extracellular matrix of animal cells (ECM) – Glycoproteins (collagen) secreted by cells – Communicates with cytoskeleton & can affect development & differentiation of cells Generalized Animal Cell http://sun.menloschool.org/~cweaver/cells/ Generalized Plant Cell http://sun.menloschool.org/~cweaver/cells/