VMU Lecture 5 Cell Biology 2023 PDF

ORGANELLES OF EUKARYOTIC CELL AND THEIR FUNCTIONS assoc. prof. Jurgita Dailidavičienė www.lsmu.lt Department of Anatomy and Physiology  Life Sciences I Cell Biology Topics of l...

ORGANELLES OF EUKARYOTIC CELL AND THEIR FUNCTIONS assoc. prof. Jurgita Dailidavičienė www.lsmu.lt Department of Anatomy and Physiology  Life Sciences I Cell Biology Topics of lecture 5 Organelles of eukaryotic cell and their functions: 1. The structural and functional features of the endoplasmic reticulum. 2. The structural and functional features of the ribosomes. 3. The structural and functional features of the Golgi apparatus. 4. The structural and functional features of the lysosomes. 2 Eukaryotic cells. A: Diagrammatic representation of an animal cell. B: Diagrammatic representation of a plant cell. C: Micrograph of an animal cell shows several membrane-bound structures, including mitochondria and a nucleus. (Fig. 2-3(A) and (B) Reproduced with permission from Nester EW, Anderson DG, Roberts CE, et al: Microbiology: A Human Perspective, 6th ed. McGraw-Hill, 2009. © McGraw-Hill Education. Fig. 2-3(C) Reproduced with permission from Thomas Fritsche, MD, PhD.) Citation: Chapter 2 Cell Structure, Riedel S, Hobden JA, Miller S, Morse SA, Mietzner TA, Detrick B, Mitchell TG, Sakanari JA, Hotez P, Mejia R. Jawetz, Melnick, & Adelberg's Medical Microbiology, 28e; 2019. Available at: https://accessmedicine.mhmedical.com/content.aspx?sectionid=217769109&bookid=2629 Accessed: September 24, 2020 Copyright © 2020 McGraw-Hill Education. All rights reserved  CELL ORGANELLES CELL ORGANELLES NONMEMBRANOUS MEMBRANOUS ONE-MEMBRANE TWO-MEMBRANE Ribosomes Plazmolema Mitochondria Microtubules Endoplasmic reticulum Plastids Golgi apparatus Microfilaments Nucleus Lysosomes Chromosomes Vacoules 4 Cross-sectional diagram of a hypothetical cell as seen with the light microscope. Individual organelles are expanded for closer examination. (Adapted with permission from Bloom and Fawcett. Reproduced with permission from Junqueira LC, Carneiro J, Kelley RO: Basic Histology, 9th ed. New York, NY: McGraw-Hill; 1998.) Citation: Chapter 2 Overview of Cellular Physiology, Barrett KE, Barman SM, Brooks HL, Yuan JJ. Ganong's Review of Medical Physiology, 26e; 2019. Available at: https://accessmedicine.mhmedical.com/content.aspx?sectionid=204290456&bookid=2525 Accessed: September 24, 2020 Copyright © 2020 McGraw-Hill Education. All rights reserved  ENDOMEMBRANE SYSTEM Includes: Nuclear envelope Endoplasmic Reticulum Golgi Apparatus Lysosomes Vesicles Plasma membrane https://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology/Book%3A_General_Bio logy_(OpenStax)/2%3A_The_Cell/04%3A_Cell_Structure/4.4%3A_The_Endomembrane_Syste 6 m_and_Proteins ENDOPLASMIC RETICULUM 7 The cytoplasm of most cells contains a convoluted membranous network called the endoplasmic reticulum. This network (reticulum) extends from the surface of the nucleus throughout most of the cytoplasm and encloses a series of intercommunicating channels called cisternae (L. cisternae, reservoirs). With a membrane surface up to 30 times that of the plasma membrane, the ER is a major site for vital cellular activities, including biosynthesis of proteins and lipids. Numerous polyribosomes attached to the membrane in some regions of ER allow two types of ER to be distinguished. https://socratic.org/questions/what-makes-endoplasmic-reticulum-smooth 8  While RER is the site for synthesis of most membrane-bound proteins, three diverse activities are associated with smooth ER: 1) lipid biosynthesis, Rough and smooth endoplasmic reticulum. 2) detoxification of potentially harmful compounds, 3) sequestration of Ca++ ions. Citation: Chapter 2 The Cytoplasm, Mescher AL. Junqueira’s Basic Histology: Text and Atlas, 15e; 2018. Available at: https://accessmedicine.mhmedical.com/content.aspx?sectionid=190276157&bookid=2430 Accessed: September 24, 2020 Copyright © 2020 McGraw-Hill Education. All rights reserved  ROUGH ENDOPLASMIC RETICULUM Rough endoplasmic reticulum (RER) consists of saclike as well as parallel stacks of flattened cisternae, each limited by membranes that are continuous with the outer membrane of the nuclear envelope. The major function of RER is production of membrane-associated proteins, proteins of many membranous organelles, and proteins to be secreted by exocytosis. Citation: Chapter 2 The Cytoplasm, Mescher AL. Junqueira’s Basic Histology: Text and Atlas, 15e; 2018. Available at: https://accessmedicine.mhmedical.com/content.aspx?sectionid=190276157&bookid=2430 Accessed: September 24, 2020 Copyright © 2020 McGraw-Hill Education. All rights reserved 10  FUNCTIONS OF ENDOPLASMIC RETICULUM RER: Production of proteins. SER: synthesis of phospholipids and steroids. detoxification of potentially harmful exogenous molecule. sequestration and controlled release of Ca2+. 11  RIBOSOMES – A SITE OF PROTEIN SYNTHESIS The ribosomes are complex structures, containing many different proteins and at least three ribosomal RNAs. https://www.slideteam.net/business_powerpoint_diagrams/95434749-style-medical-3-microbiology-1-piece- powerpoint-presentation-diagram-infographic-slide.html/ 12 Rough endoplasmic reticulum and protein translation. Messenger RNA and ribosomes meet up in the cytosol for translation. Proteins that have appropriate signal peptides begin translation, and then associate with the endoplasmic reticulum (ER) to complete translation. The association of ribosomes is what gives the ER its “rough” appearance. (Reproduced with permission from Widmaier EP, Raff H, Strang KT: Vander’s Human Physiology: The Mechanisms of Body Function, 11th ed. New York, NY: McGraw-Hill; 2008.) Citation: Chapter 2 Overview of Cellular Physiology, Barrett KE, Barman SM, Brooks HL, Yuan JJ. Ganong's Review of Medical Physiology, 26e; 2019. Available at: https://accessmedicine.mhmedical.com/content.aspx?sectionid=204290456&bookid=2525 Accessed: September 24, 2020 Copyright © 2020 McGraw-Hill Education. All rights reserved  Typically, free ribosomes synthesize proteins for use in the cytoplasm, while ribosomes bound to the endoplasmic reticulum membrane synthesize proteins that are exported from the cell or incorporated into the membrane. The sedimentation coefficient (s) of a particle characterizes its sedimentation during centrifugation. RNA and protein compositions of: (a) bacterial ribosomes; and (b) eukaryotic ribosomes. (Reprinted with permission from Brooker RJ: Genetics: Analysis & Principles, 3rd ed. New York: McGraw-Hill, 2008.) Citation: Chapter 2 Information Flow and Levels of Regulation, Schaefer G, Thompson, Jr. JN. Medical Genetics: An Integrated Approach; 2017. Available at: https://accessmedicine.mhmedical.com/content.aspx?sectionid=173743774&bookid=2247 Accessed: September 29, 2020 Copyright © 2020 McGraw-Hill Education. All rights reserved  PROTEIN TRAFFICING The movement of newly synthesized proteins in a cell is called protein trafficing. Protein traffic is characterized by common principles that make up protein targetting molecular mechanism. 15  PROTEIN TRAFFICING Protein activity and stability are changing. Proteins are targeted to specific sites in the cell or secretion to the outside of the cell. 16 One means of regulation involves sorting of the protein into various cell regions. Posttranslational sorting occurs with proteins synthesized in the cytosol. They either remain in the cytosol or are sorted to the mitochondria, chloroplasts, peroxisomes, or nucleus. Cotranslational sorting involves the signal recognition particle (SRP) detecting a short amino acid sequence near the amino terminal. These proteins are sorted first to the endoplasmic reticulum and then to the Golgi complex, lysosomes, secretory vesicles, or the plasma membrane. Note that the diagram represents snapshot points in translation, not three ribosomes translating an mRNA at the same time. (Reprinted with permission from Brooker RJ: Genetics: Analysis & Principles, 3rd ed. New York: McGraw-Hill, 2008.) Citation: Chapter 2 Information Flow and Levels of Regulation, Schaefer G, Thompson, Jr. JN. Medical Genetics: An Integrated Approach; 2017. Available at: https://accessmedicine.mhmedical.com/content.aspx?sectionid=173743774&bookid=2247 Accessed: September 29, 2020 Copyright © 2020 McGraw-Hill Education. All rights reserved  Longer-acting proteins are broken down in lysosomes, while shorter- lived ones are broken down in the 26S Polyribosomes: free or bound to the endoplasmic reticulum. proteasome. Citation: Chapter 2 The Cytoplasm, Mescher AL. Junqueira’s Basic Histology: Text and Atlas, 15e; 2018. Available at: https://accessmedicine.mhmedical.com/content.aspx?sectionid=190276157&bookid=2430 Accessed: September 24, 2020 Copyright © 2020 McGraw-Hill Education. All rights reserved RER has a highly regulated system to prevent nonfunctional proteins being forwarded to the pathway for secretion or to other organelles. New proteins that cannot be folded or assembled properly by chaperones undergo ER-associated degradation (ERAD), in which unsalvageable proteins are translocated back into the cytosol, conjugated to ubiquitin, and then degraded by proteasomes. 19 Typically, free ribosomes synthesize proteins for use in the cytoplasm, while ribosomes bound to the endoplasmic reticulum membrane synthesize proteins that are exported from the cell or incorporated into the membrane. 20  GOLGI APPARATUS 21  STRUCTURE OF GOLGI APPARATUS 1898 m. discovered Camillo Golgi https://www.delfi.lt/gyvenimas/receptai/gardziausiu-blynu- receptai.d?id=67078092 https://www.britannica.com/science/Golgi-apparatus 22 Golgi apparatus. Citation: Chapter 2 The Cytoplasm, Mescher AL. Junqueira’s Basic Histology: Text and Atlas, 15e; 2018. Available at: https://accessmedicine.mhmedical.com/content.aspx?sectionid=190276157&bookid=2430 Accessed: September 24, 2020 Copyright © 2020 McGraw-Hill Education. All rights reserved Secretory granules. Citation: Chapter 2 The Cytoplasm, Mescher AL. Junqueira’s Basic Histology: Text and Atlas, 15e; 2018. Available at: https://accessmedicine.mhmedical.com/content.aspx?sectionid=190276157&bookid=2430 Accessed: September 24, 2020 Copyright © 2020 McGraw-Hill Education. All rights reserved  GOLGI APPARATUS STRUCTURES Cisternae Vesicles – in the end of cisternae Dictyosomes – a group of parallel, flattened cisternae with flared ends. 25  GOLGI APPARATUS STRUCTURES Cis – face – Golgi-receiving region Medial region Trans – face – distinguishing region http://oregonstate.edu/instruction/bi314/summer09/Fig-10-27-0.jpg 26  ENZYMES OF GOLGI APPARATUS Golgi saccules at sequential locations contain different enzymes at different cis, medial, and trans levels Cis face – mannosidase I Medial – mannosidase II Trans face – galactosyltransferase sialyltransferase. 27  FUNCTIONS OF GOLGI APPARATUS 1. Modifying secretory products 2. Sorting secretory products 3. Forming transport vacuoles. Golgi apparatus completes posttranslational modifications of proteins produced in the RER and then packages and addresses these proteins to their proper destinations. 28  SUMMARY  The Golgi apparatus is a dynamic organelle consisting of stacked membranous cisternae in which proteins made in RER are processed further and packaged for secretion or other roles.  Proteins in transport vesicles enter the cis or receiving face of the Golgi, move through medial cisternae of the Golgi network for enzymatic modifications, and are released in other vesicles at the trans face.  Vesicle movement through the Golgi apparatus is guided by specific coat proteins such as COPII and COPI.  Important protein modifications in the Golgi apparatus include sulfation and many glycosylation reactions. Modified proteins leave the Golgi apparatus after packaging in vesicles with coat proteins that direct movement to lysosomes, the plasma membrane, or secretion by exocytosis. 29 Summary of functions within the Golgi apparatus. Citation: Chapter 2 The Cytoplasm, Mescher AL. Junqueira’s Basic Histology: Text and Atlas, 15e; 2018. Available at: https://accessmedicine.mhmedical.com/content.aspx?sectionid=190276157&bookid=2430 Accessed: September 24, 2020 Copyright © 2020 McGraw-Hill Education. All rights reserved LYSOSOMES 31  Lysosomes – 1949 m. developed by Christian De Duve A typical animal cell can contain up to 100 lysosomes, and phagocytic macrophage cells can contain up to 1000. Mitochondria Peroxysome fragment Lysosome https://petelawrieblog.com/obrazovanie/81677-lizosomy-eto-kletochnye- sanitary.html http://faculty.muhs.edu/klestinski/cellcity/lysosomedata.htm 32 Lysosomes. Citation: Chapter 2 The Cytoplasm, Mescher AL. Junqueira’s Basic Histology: Text and Atlas, 15e; 2018. Available at: https://accessmedicine.mhmedical.com/content.aspx?sectionid=190276157&bookid=2430 Accessed: September 24, 2020 Copyright © 2020 McGraw-Hill Education. All rights reserved Lysosomal functions. Citation: Chapter 2 The Cytoplasm, Mescher AL. Junqueira’s Basic Histology: Text and Atlas, 15e; 2018. Available at: https://accessmedicine.mhmedical.com/content.aspx?sectionid=190276157&bookid=2430 Accessed: September 24, 2020 Copyright © 2020 McGraw-Hill Education. All rights reserved 1. Lysosomes are spherical membrane-enclosed vesicles that function as sites of intracellular digestion and are particularly numerous in cells active after the various types of endocytosis. 2. In the cytoplasm of the cell there are large, somewhat irregular structures surrounded by membranes. The interior of these structures, which are called lysosomes, is more acidic than the rest of the cytoplasm. 3. The main enzyme – acid phosphatase. Lysosomes can contain over 40 types of hydrolytic enzymes, hydrolytically degrading proteins, nucleic acids, carbohydrates and lipids. 4. Cytosolic components are protected from these enzymes by the membrane surrounding lysosomes and because the enzymes have optimal activity at an acidic pH (~5.0). Any leaked lysosomal enzymes are practically inactive at the pH of cytosol (~7.2) and 35 harmless to the cell.  DEFINITIONS RELATING TO LYSOSOME ACTIVITIES Heterophagia is the breakdown of a foreign substance that is absorbed by endocytosis. Autophagy – the breakdown of own materials, e.g. storage nutrients as well as macromolecules or organelles that have lost their functional activity. Autolysis is the digestion of cells due to pathology or aging due to the breakdown of lysosomal membranes 36 Autophagy. Citation: Chapter 2 The Cytoplasm, Mescher AL. Junqueira’s Basic Histology: Text and Atlas, 15e; 2018. Available at: https://accessmedicine.mhmedical.com/content.aspx?sectionid=190276157&bookid=2430 Accessed: September 24, 2020 Copyright © 2020 McGraw-Hill Education. All rights reserved Primary lysosomes emerge from the Golgi apparatus containing inactive acid hydrolases specific for degrading a wide variety of cellular macromolecules Secondary lysosomes are more heterogeneous, having fused with vesicles produced by endocytosis that contain material to be digested by the hydrolytic enzymes. During autophagy, lysosomes digest unneeded or nonfunctional organelles after these are surrounded by membrane that then fuses with a lysosome. Products of digestion in secondary lysosomes are released to the cytoplasm for reuse; final condensed vesicles containing any indigestible molecules are called residual bodies. 38 39  AUTOLYSIS Disruption of cell contents acting on lysosome-derived hydrolases called autolysis. 40  LIPOFUSCIN – OLD AGE PIGMENT https://for-long-life.com/en-us/blog/aging-spots-from-lipofuscin-removed-by-riboflavin 41 Biological functions of lysosomes: 1. Degradation of substances released from the environment by endocytosis or phagocytosis. 2. In the circulation of the internal materials and structures of the cell, lysosomes perform the function of a "recycling" system. Specialized liver Kupfer cells phagocytose old erythrocytes and disrupt them in lysosomes. Residues of mitochondria, peroxisomes, other structures are removed by autophagy. 3. Cell-derived lysosomal enzymes perform specific functions and are important in embryogenesis processes. 42  LISOSOMAL DISEASES Lysosomal diseases are a group of diseases caused by genetic heredity. Their pathomechanism is based on the excessive accumulation of macromolecules in cell lysosomes. The accumulation process occurs due to a single deficiency of lysosomal enzymes. The accumulation of macromolecules causes an increase in lysosomes, resulting in destroyed cell function. Accumulated macromolecules usually damage the CNS. 43