BIOLOGY CONCEPTS & CONNECTIONS Fourth Edition Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Neil A. Campbell Jane B. Reece Lawrence G. Mitchell Martha R. Taylor From PowerPoint ® Lectures for Biology: Concepts & Connections CHAPTER 4 A Tour of the Cell Modules 4.6 – 4.14

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The largest organelle is usually the nucleus Most cells have one nucleus but others may have multiple or lobed nuclei The nucleus is separated from the cytoplasm by the nuclear envelope. The envelope is a double lipid bilayer membrane with nuclear pores. The nucleus is the cellular control center –It contains the DNA that directs the cell’s activities –It contains a nucleolus region for the synthesis of ribosomal subunits The nucleus is the cell’s genetic control center

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Cells with multiple nuclei Some muscle cells and megakaryocytes

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

The membranes of the cell

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The Phospholipid

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The endomembrane system is a collection of membranous organelles –These organelles manufacture and distribute cell products –The endomembrane system divides the cell into compartments –Endoplasmic reticulum (ER) is part of the endomembrane system 4.7 Many cell organelles are related through the endomembrane system

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 4.6 Chromatin Nucleolus Pore NUCLEUS Two membranes of nuclear envelope ROUGH ENDOPLASMIC RETICULUM Ribosomes

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The rough ER manufactures membranes Ribosomes on its surface produce proteins 4.8 Rough endoplasmic reticulum makes membrane and proteins Transport vesicle buds off Ribosome Sugar chain Glycoprotein Secretory (glyco-) protein inside transport vesicle ROUGH ER Polypeptide Figure 4.8

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Smooth ER synthesizes lipids In some cells, like liver cells, it regulates carbohydrate metabolism by removing a phosphate from glucose phosphate and allowing the glucose o enter the blood. In liver it also helps to break down toxins and drugs by adding a hydroxyl group to help solubilize them in water so that they can be excreted. In muscle the ER stores calcium against its concentration gradient until a signal allows its release and a muscle contraction ensues. 4.9 Smooth endoplasmic reticulum has a variety of functions

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings SMOOTH ER ROUGH ER Nuclear envelope Ribosomes SMOOTH ERROUGH ER Figure 4.9

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The Golgi apparatus consists of stacks of membranous sacs –These receive and modify ER products, then send them on to other organelles or to the cell membrane in vessicles –The cis side of the golgi faces the ER while the trans faces the outer membrane 4.10 The Golgi apparatus finishes, sorts, and ships cell products

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The Golgi apparatus Golgi apparatus “Receiving” side of Golgi apparatus Transport vesicle from ER New vesicle forming Transport vesicle from the Golgi Golgi apparatus “Shipping” side of Golgi apparatus Figure 4.10

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Lysosomes are sacs of digestive enzymes budded off the Golgi Because they are separate compartments, digestive enzymes can be stored that function at different pH’s. The compartment protects the rest of the cell from degredation by theses enzymes Lysosomes digest the cell’s food and wastes LYSOSOME Nucleus Figure 4.11A

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Lysosomal enzymes –digest food –destroy bacteria –recycle damaged organelles –function in embryonic development in animals

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 4.11B Rough ER Transport vesicle (containing inactive hydrolytic enzymes) Golgi apparatus Plasma membrane LYSOSOMES “Food” Engulfment of particle Food vacuole Digestion Lysosome engulfing damaged organelle

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Lysosomal storage diseases are hereditary –They interfere with other cellular functions –Examples: Pompe’s disease, Tay-Sachs disease 4.12 Connection: Abnormal lysosomes can cause fatal diseases

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Plant cells contain a large central vacuole –The vacuole has lysosomal and storage functions –It may take up nearly 90% of the cell’s space 4.13 Vacuoles function in the general maintenance of the cell Central vacuole Nucleus Figure 4.13A

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Protists may have contractile vacuoles Figure 4.13B Nucleus Contractile vacuoles –These pump out excess water –Paramecium with contractile vacuole

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The various organelles of the endomembrane system are interconnected structurally and functionally 4.14 A review of the endomembrane system Transport vesicle from ER Rough ER Transport vesicle from Golgi Plasma membrane Vacuole Lysosome Golgi apparatus Nuclear envelope Smooth ER Nucleus Figure 4.14