Cellular Biology 1
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Bacterial Cell Membrane
BACTERIAL CELL MEMBRANE Dr. Rakesh Sharda Department of Veterinary Microbiology NDVSU College of Veterinary Sc. & A.H., MHOW CYTOPLASMIC MEMBRANE ➢The cytoplasmic membrane, also called a cell membrane or plasma membrane, is about 7 nanometers (nm; 1/1,000,000,000 m) thick. ➢It lies internal to the cell wall and encloses the cytoplasm of the bacterium. ➢It is the most dynamic structure of a prokaryotic cell. Structure of cell membrane ➢The structure of bacterial plasma membrane is that of unit membrane, i.e., a fluid phospholipid bilayer, composed of phospholipids (40%) and peripheral and integral proteins (60%) molecules. ➢The phospholipids of bacterial cell membranes do not contain sterols as in eukaryotes, but instead consist of saturated or monounsaturated fatty acids (rarely, polyunsaturated fatty acids). ➢Many bacteria contain sterol-like molecules called hopanoids. ➢The hopanoids most likely stabilize the bacterial cytoplasmic membrane. ➢The phospholipids are amphoteric molecules with a polar hydrophilic glycerol "head" attached via an ester bond to two non-polar hydrophobic fatty acid tails. ➢The phospholipid bilayer is arranged such that the polar ends of the molecules form the outermost and innermost surface of the membrane while the non-polar ends form the center of the membrane Fluid mosaic model ➢The plasma membrane contains proteins, sugars, and other lipids in addition to the phospholipids. ➢The model that describes the arrangement of these substances in lipid bilayer is called the fluid mosaic model ➢Dispersed within the bilayer are various structural and enzymatic proteins, which carry out most membrane functions. ➢Some membrane proteins are located and function on one side or another of the membrane (peripheral proteins). -
Construction and Loss of Bacterial Flagellar Filaments
biomolecules Review Construction and Loss of Bacterial Flagellar Filaments Xiang-Yu Zhuang and Chien-Jung Lo * Department of Physics and Graduate Institute of Biophysics, National Central University, Taoyuan City 32001, Taiwan; [email protected] * Correspondence: [email protected] Received: 31 July 2020; Accepted: 4 November 2020; Published: 9 November 2020 Abstract: The bacterial flagellar filament is an extracellular tubular protein structure that acts as a propeller for bacterial swimming motility. It is connected to the membrane-anchored rotary bacterial flagellar motor through a short hook. The bacterial flagellar filament consists of approximately 20,000 flagellins and can be several micrometers long. In this article, we reviewed the experimental works and models of flagellar filament construction and the recent findings of flagellar filament ejection during the cell cycle. The length-dependent decay of flagellar filament growth data supports the injection-diffusion model. The decay of flagellar growth rate is due to reduced transportation of long-distance diffusion and jamming. However, the filament is not a permeant structure. Several bacterial species actively abandon their flagella under starvation. Flagellum is disassembled when the rod is broken, resulting in an ejection of the filament with a partial rod and hook. The inner membrane component is then diffused on the membrane before further breakdown. These new findings open a new field of bacterial macro-molecule assembly, disassembly, and signal transduction. Keywords: self-assembly; injection-diffusion model; flagellar ejection 1. Introduction Since Antonie van Leeuwenhoek observed animalcules by using his single-lens microscope in the 18th century, we have entered a new era of microbiology. -
Cell Membrane
John Lenyo Corrina Perez Hazel Owens Cell Membrane http://micro.magnet.fsu.edu/cells/plasmamembrane/plasmamembrane.html • Cell membranes are composed of proteins and lipids. • Since they are made up of mostly lipids, only certain substances can move through. spmbiology403.blogspot.com •Phospholipids are the most abundant type of lipid found in the membrane. Phospholipids are made up of two layers, the outer and inner layers. The inside layer is made of hydrophobic fatty acid tails, while the outer layer is made up of hydrophilic polar heads that are pointed toward the water. academic.brooklyn.cuny.edu •Membrane structure relies on the tendency of fatty acid molecules to spread on the surface of water. • Membrane proteins (which take up half of the membrane) determine what gets into and leaves the cell. •Glycolipids are found on the outer part of the cell membrane. Single Chain vs. Phospholipid • Single chain lipids were assumed to be the first of those to form cell membranes with the more complex phospholipids evolving later • Phospholipids can be synthesized in an abiotic environment without enzymes now • Phosphoplipid bilayers now make up the plasma cell membranes that regulate movement into and out of prokaryotic and eukaryotic cells. Single chain lipid http://web.nestucca.k12.or.us/nvhs/staff/whitehead/homewor http://clincancerres.aacrjournals.org/content/11/5/2018/F1. k.htm expansion Types of Lipids • Today Plasma Membranes are made primarily of phospholipids • It is thought that early membranes may have been made of simpler fatty acids. http://exploringorigins.org/fattyacids.html Properties of Fatty Acids • They are Ampipathic, meaning that they have a hydrophobic (“water hating”) end and a hydrophilic (water loving”) end. -
Cell Wall Constrains Lateral Diffusion of Plant Plasma-Membrane Proteins
Cell wall constrains lateral diffusion of plant SEE COMMENTARY plasma-membrane proteins Alexandre Martinièrea, Irene Lavagia, Gayathri Nageswarana, Daniel J. Rolfeb, Lilly Maneta-Peyretc, Doan-Trung Luud, Stanley W. Botchwayb, Stephen E. D. Webbb, Sebastien Mongrandc, Christophe Maureld, Marisa L. Martin-Fernandezb, Jürgen Kleine-Vehne, Jirí Frimlf, Patrick Moreauc, and John Runionsa,1 aDepartment of Biological and Medical Sciences, Oxford Brookes University, Oxford OX3 0BP, United Kingdom; bCentral Laser Facility, Research Complex at Harwell, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Oxfordshire OX11 0QX, United Kingdom; cLaboratoire de Biogenèse Membranaire, Unité Mixte de Recherche 5200 Centre National de la Recherche Scientifique, Université Bordeaux Segalen, 33076 Bordeaux, France; dLaboratoire de Biochimie et Physiologie Moléculaire des Plantes, Institut de Biologie Intégrative des Plantes, Unité Mixte de Recherche 5004, Centre National de la Recherche Scientifique/Unité Mixte de Recherche 0386 Institut National de la Recherche Agronomique, 34060 Montpellier, France; eDepartment of Applied Genetics and Cell Biology, University of Natural Resources and Life Sciences, 1190 Vienna, Austria; and fDepartment of Plant Biotechnology and Genetics, Ghent University, 9052 Ghent, Belgium Edited by Daniel J. Cosgrove, Pennsylvania State University, University Park, PA, and approved May 16, 2012 (received for review February 3, 2012) A cell membrane can be considered a liquid-phase plane in which yeast lines lacking -
DNA Extraction
DNA Extraction Learning Objectives: Students learn about DNA, cell structure, and basic chemical separations. GRADE LEVEL SNEAK PEAK inside … ACTIVITY 4–8 Students extract DNA from strawberries. SCIENCE TOPICS STUDENT SUPPLIES Solutions and Mixtures see next page for more supplies Techniques strawberries Organic and Biochemistry sealing plastic bags dish soap PROCESS SKILLS salt meat tenderizer Describing and Defining isopropyl alcohol, etc…. Explaining Evaluating ADVANCE PREPARATION see next page for more details GROUP SIZE dilute soap mix tenderizer and salt together, etc…. 1–3 OPTIONAL EXTRAS DEMONSTRATION If available, goggles are recommended for this activity. Modeling the Procedure (p. C - 22) EXTENSIONS Animal DNA (p. C - 29) Other DNA Sources (p. C - 30) TIME REQUIRED Advance Preparation Set Up Activity Clean Up 15 minutes 15 minutes 20 minutes 15 minutes the day before DNA Extraction C – 19 Chemistry in the K–8 Classroom Grades 4–8 2007, OMSI SUPPLIES Item Amount Needed strawberries 1 per group sealing plastic bags (e.g., ZiplocTM) 1 per group liquid dish soap ½ teaspoon per group 99% isopropyl alcohol (or lower, e.g., 70% ¼ cup per group rubbing alcohol) meat tenderizer 1 tablespoon per class OR OR papaya or pineapple juice ¼ cup juice per class salt 1 tablespoon per class tall, clear, narrow plastic cups (8 oz. or 12 oz.) 2 per group plastic spoon 1 per group pop-top squeeze bottles (e.g., water or sports drink) 1 per group freezer or bucket of ice 1 per class For Extension or Demonstration supplies, see the corresponding section. ADVANCE PREPARATION Supplies Preparation Strawberries: Purchase fresh or thawed, green tops on or off. -
Identification of Oxa1 Homologs Operating in the Eukaryotic
Report Identification of Oxa1 Homologs Operating in the Eukaryotic Endoplasmic Reticulum Graphical Abstract Authors S. Andrei Anghel, Philip T. McGilvray, Ramanujan S. Hegde, Robert J. Keenan Correspondence [email protected] In Brief The absence of Oxa1/Alb3/YidC homologs in the eukaryotic endomembrane system has been a mystery. Now, Anghel et al. identify three ER-resident proteins, Get1, EMC3, and TMCO1, as remote homologs of Oxa1/ Alb3/YidC proteins and show that TMCO1 possesses YidC-like biochemical properties. This defines the ‘‘Oxa1 superfamily’’ of membrane protein biogenesis factors. Highlights d The ‘‘Oxa1 superfamily’’ comprises a group of membrane protein biogenesis factors d Three ER-resident proteins, Get1, EMC3, and TMCO1, are members of the superfamily d TMCO1, similar to bacterial YidC, associates with ribosomes and the Sec translocon Anghel et al., 2017, Cell Reports 21, 3708–3716 December 26, 2017 ª 2017 Elsevier Inc. https://doi.org/10.1016/j.celrep.2017.12.006 Cell Reports Report Identification of Oxa1 Homologs Operating in the Eukaryotic Endoplasmic Reticulum S. Andrei Anghel,1,2 Philip T. McGilvray,1 Ramanujan S. Hegde,3 and Robert J. Keenan1,4,* 1Department of Biochemistry and Molecular Biology 2Cell and Molecular Biology Graduate Program The University of Chicago, 929 East 57th Street, Chicago, IL 60637, USA 3MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK 4Lead Contact *Correspondence: [email protected] https://doi.org/10.1016/j.celrep.2017.12.006 SUMMARY proteins are inserted into the ER membrane by the WRB-CAML complex (Get1-Get2 in yeast; Mariappan et al., 2011; Schuldiner Members of the evolutionarily conserved Oxa1/Alb3/ et al., 2008; Vilardi et al., 2011; Wang et al., 2011, 2014; Yamamoto YidC family mediate membrane protein biogenesis at and Sakisaka, 2012). -
Introduction and Cell Membrane
Introduction and Cell Membrane Peter Takizawa Department of Cell Biology Topics for today’s lecture • Course organization • Why cell biology • Cell membrane Cell Biology comprises a variety of activities that discuss basic science and disease. Lectures Website Cell Biology Clinical Histology Correlations Website !The Cell Biology course proper consists of three distinct activities: lectures, histology labs and clinical correlations. In addition, there are two electives that are associated with Cell Biology: molecular and cellular basis of disease and bench to bedside. Lectures will discuss the principles and concepts of modern cellular and molecular biology, focusing on the systems and mechanisms that allow cells to survive and perform specific functions in our bodies. The first part of the course will discuss the !systems and mechanisms that are common to most cells. The second part will discuss how the different types of cells in our bodies, utilize and modify those systems to perform specific biological functions. Histology examines the structure and functions of cells and how cells form tissues and organs. Histology places the cellular mechanisms presented in lecture into the context of cell and tissue structure. Histology also demonstrates how the !organization of cell and tissues allows organs to perform the physiological functions. Clinical correlations introduce students to clinical topics and medical terminology and demonstrate connections between basic science and disease. These presentations by physician-scientists, who are leaders in their fields, will sometimes include patients. You will notified when a patient is present. Why study cell biology to be a physician In order to understand how disease arises and how to treat disease, we need to learn how we work under normal conditions. -
Passive and Active Transport
Passive and Active Transport 1. Thermodynamics of transport 2. Passive-mediated transport 3. Active transport neuron, membrane potential, ion transport Membranes • Provide barrier function – Extracellular – Organelles • Barrier can be overcome by „transport proteins“ – To mediate transmembrane movements of ions, Na+, K+ – Nutrients, glucose, amino acids etc. – Water (aquaporins) 1) Thermodynamics of Transport • Aout <-> Ain (ressembles a chemical equilibration) o‘ • GA - G A = RT ln [A] • ∆GA = GA(in) - GA(out) = RT ln ([A]in/[A]out) • GA: chemical potential of A o‘ • G A: chemical potential of standard state of A • If membrane has a potential, i.e., plasma membrane: -100mV (inside negative) then GA is termed the electrochemical potential of A Two types of transport across a membrane: o Nonmediated transport occurs by passive diffusion, i.e., O2, CO2 driven by chemical potential gradient, i.e. cannot occur against a concentration gradient o Mediated transport occurs by dedicated transport proteins 1. Passive-mediated transport/facilitated diffusion: [high] -> [low] 2. Active transport: [low] -> [high] May require energy in form of ATP or in form of a membrane potential 2) Passive-mediated transport Substances that are too large or too polar to diffuse across the bilayer must be transported by proteins: carriers, permeases, channels and transporters A) Ionophores B) Porins C) Ion Channels D) Aquaporins E) Transport Proteins A) Ionophores Organic molecules of divers types, often of bacterial origin => Increase the permeability of a target membrane for ions, frequently antibiotic, result in collapse of target membrane potential by ion equilibration 1. Carrier Ionophore, make ion soluble in membrane, i.e. valinomycin, 104 K+/sec 2. -
Evidence for a Respiratory Chain in the Chloroplast
Proc. NatL Acad. Sci. USA Vol. 79, pp. 4352-4356, July 1982 Cell Biology Evidence for a respiratory chain in the chloroplast (photosynthesis/respiration/starch degradation/evolution) PIERRE BENNOUN Institut de Biologie Physico-Chimique, 13, rue Pierre et Marie Curie, 75005, Paris, France Communicated by Pierre Joliot, April 12, 1982 ABSTRACT Evidence is given for the existence ofan electron in 20 ml of 20 mM N-tris(hydroxymethyl)methylglycine(Tri- transport pathway to oxygen in the thylakoid membranes ofchlo- cine)/KOH, pH 7.8/10 mM NaCl/10 mM MgCl2/1 mM K2- roplasts (chlororespiration). Plastoquinone is shown to be a redox HPO4/0.1 M sucrose/5% Ficoll. The cell suspension was carrier common to both photosynthetic and chlororespiratory passed through a Yeda press operated at 90 kg/cm2, diluted pathways. It is shown that, in dark-adapted chloroplasts, an elec- with 200 ml of Ficoll-lacking buffer, and centrifuged, and the trochemical gradient is built up across the thylakoid membrane pellet was suspended in the same buffer. by transfer of electrons through the chlororespiratory chain as Chlorophyll fluorescence kinetics and luminescence mea- well as by reverse functioning of the chloroplast ATPases. It is surements were performed as described (9). proposed that these mechanisms ensure recycling ofthe ATP and NAD(P)H generated by the glycolytic pathway converting starch into triose phosphates. Chlororespiration is thus an 02-uptake RESULTS process distinct from photorespiration and the Mehler reaction. The plastoquinone (PQ) pool ofchloroplast is a redox carrier of The evolutionary significance of chlororespiration is discussed. the photosynthetic electron transport chain. -
Cilia and Flagella: from Discovery to Disease Dylan J
Dartmouth Undergraduate Journal of Science Volume 20 Article 2 Number 1 Assembly 2017 Cilia and Flagella: From Discovery to Disease Dylan J. Cahill Dylan Cahill, [email protected] Follow this and additional works at: https://digitalcommons.dartmouth.edu/dujs Part of the Engineering Commons, Life Sciences Commons, Medicine and Health Sciences Commons, Physical Sciences and Mathematics Commons, and the Social and Behavioral Sciences Commons Recommended Citation Cahill, Dylan J. (2017) "Cilia and Flagella: From Discovery to Disease," Dartmouth Undergraduate Journal of Science: Vol. 20 : No. 1 , Article 2. Available at: https://digitalcommons.dartmouth.edu/dujs/vol20/iss1/2 This Research Article is brought to you for free and open access by the Student-led Journals and Magazines at Dartmouth Digital Commons. It has been accepted for inclusion in Dartmouth Undergraduate Journal of Science by an authorized editor of Dartmouth Digital Commons. For more information, please contact [email protected]. BIOLOGY Cilia and Flagella: FromCilia and Discovery Flagella: to Disease From Discovery to Disease BY DYLAN CAHILL ‘18 Introduction certain insect sperm fagella (3, 5, 6). A unique Figure 1: Chlamydomonas intracellular transport mechanism known as reinhardtii, a single-celled, bi- In 1674, peering through the lens of a crude flagellate green alga, viewed intrafagellar transport is responsible for the light microscope, Antoni van Leeuwenhoek with a scanning electron assembly and maintenance of these organelles Chlamydomonas observed individual living cells for the frst time microscope. is (3, 6). Cilia and fagella are primarily composed a model organism in flagellar in history (1). He noted long, thin appendages of the protein tubulin, which polymerizes into dynamics and motility studies. -
Cell Structure and Function in the Bacteria and Archaea
4 Chapter Preview and Key Concepts 4.1 1.1 DiversityThe Beginnings among theof Microbiology Bacteria and Archaea 1.1. •The BacteriaThe are discovery classified of microorganismsinto several Cell Structure wasmajor dependent phyla. on observations made with 2. theThe microscope Archaea are currently classified into two 2. •major phyla.The emergence of experimental 4.2 Cellscience Shapes provided and Arrangements a means to test long held and Function beliefs and resolve controversies 3. Many bacterial cells have a rod, spherical, or 3. MicroInquiryspiral shape and1: Experimentation are organized into and a specific Scientificellular c arrangement. Inquiry in the Bacteria 4.31.2 AnMicroorganisms Overview to Bacterialand Disease and Transmission Archaeal 4.Cell • StructureEarly epidemiology studies suggested how diseases could be spread and 4. Bacterial and archaeal cells are organized at be controlled the cellular and molecular levels. 5. • Resistance to a disease can come and Archaea 4.4 External Cell Structures from exposure to and recovery from a mild 5.form Pili allowof (or cells a very to attach similar) to surfacesdisease or other cells. 1.3 The Classical Golden Age of Microbiology 6. Flagella provide motility. Our planet has always been in the “Age of Bacteria,” ever since the first 6. (1854-1914) 7. A glycocalyx protects against desiccation, fossils—bacteria of course—were entombed in rocks more than 3 billion 7. • The germ theory was based on the attaches cells to surfaces, and helps observations that different microorganisms years ago. On any possible, reasonable criterion, bacteria are—and always pathogens evade the immune system. have been—the dominant forms of life on Earth. -
The Electrochemical Gradient of Protons and Its Relationship to Active Transport in Escherichia Coli Membrane Vesicles
Proc. Natl. Acad. Sci. USA Vol. 73, No. 6, pp. 1892-1896, June 1976 Biochemistry The electrochemical gradient of protons and its relationship to active transport in Escherichia coli membrane vesicles (flow dialysis/membrane potential/energy transduction/lipophilic cations/weak acids) SOFIA RAMOS, SHIMON SCHULDINER*, AND H. RONALD KABACK The Roche Institute of Molecular Biology, Nutley, New Jersey 07110 Communicated by B. L. Horecker, March 17, 1976 ABSTRACT Membrane vesicles isolated from E. coli gen- presence of valinomycin), a respiration-dependent membrane erate a trans-membrane proton gradient of 2 pH units under potential (AI, interior negative) of approximately -75 mV in appropriate conditions when assayed by flow dialysis. Using E. coli membrane vesicles has been documented (6, 13, 14). the distribution of weak acids to measure the proton gradient (ApH) and the distribution of the lipophilic cation triphenyl- Moreover it has been shown that the potential causes the ap- methylphosphonium to measure the electrical potential across pearance of high affinity binding sites for dansyl- and azido- the membrane (AI), the vesicles are shown to generate an phenylgalactosides on the outer surface of the membrane (4, electrochemical proton gradient (AiH+) of approximately -180 15) and that the potential is partially dissipated as a result of mV at pH 5.5 in the presence of ascorbate and phenazine lactose accumulation (6). Although these findings provide ev- methosulfate, the major component of which is a ApH of about idence for the chemiosmotic hypothesis, it has also been dem- -110 mV. As external pH is increased, ApH decreases, reaching o at pH 7.5 and above, while AI remains at about -75 mV and onstrated (6, 16) that vesicles are able to accumulate lactose and internal pH remains at pH 7.5.