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Regents Biology Ch. 19 - Viruses Overview: A Borrowed Life Viruses called bacteriophages can infect and set in motion a genetic takeover of bacteria, such as Escherichia coli Viruses lead “a kind of borrowed life” between life-forms and chemicals The origins of molecular biology lie in early studies of viruses that infect bacteria © 2011 Pearson Education, Inc.
Regents Biology Figure 19.1 0.5 mm
Regents Biology Concept 19.1: A virus consists of a nucleic acid surrounded by a protein coat Structure of Viruses Viruses are not cells A virus is a very small infectious particle consisting of nucleic acid enclosed in a protein coat and, in some cases, a membranous envelope © 2011 Pearson Education, Inc.
Regents Biology Viral Genomes Viral genomes may consist of either Double- or single-stranded DNA, or Double- or single-stranded RNA Depending on its type of nucleic acid, a virus is called a DNA virus or an RNA virus © 2011 Pearson Education, Inc.
Regents Biology Capsids and Envelopes A capsid is the protein shell that encloses the viral genome Capsids are built from protein subunits called capsomeres A capsid can have various structures © 2011 Pearson Education, Inc.
Regents Biology Figure 19.3 Capsomere of capsid RNA Capsomere DNA Glycoprotein Glycoproteins Membranous envelope RNA Capsid Head DNA Tail sheath Tail fiber 18 250 nm 80 225 nm 70–90 nm (diameter) 80–200 nm (diameter) 20 nm 50 nm (a) Tobacco mosaic virus (b) Adenoviruses (c) Influenza viruses(d) Bacteriophage T4
Regents Biology Some viruses have membranous envelopes that help them infect hosts Viral envelopes surround the capsids of influenza viruses and many other viruses found in animals Derived from the host cell’s membrane Contain a combination of viral and host cell molecules © 2011 Pearson Education, Inc.
Regents Biology Bacteriophages, also called phages, are viruses that infect bacteria Have the most complex capsids found among viruses Have an elongated capsid head that encloses their DNA A protein tail piece attaches the phage to the host and injects the phage DNA inside http://scitechdaily.com/video-animation-on- how-a-flu-virus-works/ http://scitechdaily.com/video-animation-on- how-a-flu-virus-works/ © 2011 Pearson Education, Inc.
Regents Biology Overview: Masters of Adaptation Utah’s Great Salt Lake can reach a salt concentration of 32% Its pink color comes from living prokaryotes Ch. 27 - Prokaryotes © 2011 Pearson Education, Inc.
Regents Biology Thrive almost everywhere, including places that are too: Acidic Salty Cold/Hot Most are microscopic, but what they lack in size they make up for in #s There are more in a handful of fertile soil than the number of people who have ever lived Prokaryotes are divided into two domains: Bacteria Archaea © 2011 Pearson Education, Inc. Prokaryotes
Regents Biology Concept 27.1: Structural and functional adaptations contribute to prokaryotic success Most likely 1 st organisms on Earth Most are unicellular, although some species form colonies Sizes are usually 0.5–5 µm Eykaryotic cells are usually 10–100 µm Come in a variety of shapes, the 3 most common shapes are: spheres (cocci) rods (bacilli) spirals © 2011 Pearson Education, Inc.
Regents Biology Cell-Surface Structures Cell wall: Maintains cell shape Protects the cell Prevents cell from bursting in a hypotonic environment A eukaryotic cell wall is made of cellulose or chitin Bacterial cell walls contain peptidoglycan A network of sugar polymers cross-linked by polypeptides © 2011 Pearson Education, Inc.
Regents Biology Archaea contain polysaccharides and proteins but lack peptidoglycan Scientists use the Gram stain to classify bacteria by cell wall composition Gram-positive bacteria have simpler walls with a large amount of peptidoglycan Gram-negative bacteria have less peptidoglycan and an outer membrane that can be toxic © 2011 Pearson Education, Inc.
Regents Biology Figure 27.3 (a) Gram-positive bacteria: peptidoglycan traps crystal violet. Gram-positive bacteria Peptido- glycan layer Cell wall Plasma membrane 10 m Gram-negative bacteria Outer membrane Peptido- glycan layer Plasma membrane Cell wall Carbohydrate portion of lipopolysaccharide (b) Gram-negative bacteria: crystal violet is easily rinsed away, revealing red dye.
Regents Biology Many antibiotics target peptidoglycan and damage bacterial cell walls Gram-negative bacteria are more likely to be antibiotic resistant A polysaccharide or protein layer called a capsule covers many prokaryotes © 2011 Pearson Education, Inc.
Regents Biology Figure 27.4 Bacterial cell wall Bacterial capsule Tonsil cell 200 nm
Regents Biology Some prokaryotes have fimbriae, which allow them to stick to their substrate or other individuals in a colony Pili (or sex pili) are longer than fimbriae and allow prokaryotes to exchange DNA © 2011 Pearson Education, Inc.
Regents Biology Figure 27.5 Fimbriae 1 m
Regents Biology Motility In a heterogeneous environment, many bacteria exhibit taxis: the ability to move toward or away from a stimulus Chemotaxis is the movement toward or away from a chemical stimulus Towards nutrients Away from toxins © 2011 Pearson Education, Inc.
Regents Biology Most motile bacteria propel themselves by flagella scattered about the surface or concentrated at one or both ends Flagella of bacteria, archaea, and eukaryotes are composed of different proteins and likely evolved independently © 2011 Pearson Education, Inc.
Regents Biology Figure 27.6 Flagellum Hook Motor Filament Rod Peptidoglycan layer Plasma membrane Cell wall 20 nm
Regents Biology Evolutionary Origins of Bacterial Flagella Bacterial flagella are composed of a motor, hook, and filament Many of the flagella’s proteins are modified versions of proteins that perform other tasks in bacteria Flagella likely evolved as existing proteins were added to an ancestral secretory system This is an example of exaptation, where existing structures take on new functions through descent with modification © 2011 Pearson Education, Inc.
Regents Biology Internal Organization and DNA Prokaryotic cells usually lack complex compartmentalization Some prokaryotes do have specialized membranes that perform metabolic functions These are usually infoldings of the plasma membrane © 2011 Pearson Education, Inc.
Regents Biology The prokaryotic genome has less DNA than the eukaryotic genome Most of the genome consists of a circular chromosome The chromosome is not surrounded by a membrane; it is located in the nucleoid region Some species of bacteria also have smaller rings of DNA called plasmids © 2011 Pearson Education, Inc.
Regents Biology Figure 27.8 Chromosome Plasmids 1 m
Regents Biology There are some differences between prokaryotes and eukaryotes in DNA replication, transcription, and translation These allow people to use some antibiotics to inhibit bacterial growth without harming themselves © 2011 Pearson Education, Inc.
Regents Biology Reproduction and Adaptation Prokaryotes reproduce quickly by binary fission and can divide every 1–3 hours Key features of prokaryotic reproduction: They are small They reproduce by binary fission They have short generation times © 2011 Pearson Education, Inc.
Regents Biology Many prokaryotes form metabolically inactive endospores, which can remain viable in harsh conditions for centuries © 2011 Pearson Education, Inc.
Regents Biology Figure 27.9 Coat Endospore 0.3 m
Regents Biology Their short generation time allows prokaryotes to evolve quickly For example, adaptive evolution in a bacterial colony was documented in a lab over 8 years Prokaryotes are not “primitive” but are highly evolved © 2011 Pearson Education, Inc.
Chapter 20 Viruses and Bacteria Section 1: Viruses Section 2: Bacteria.
Ch. 19 Viruses Objective: EK 3.C.3: Viral replication results in genetic variation, and viral infection can introduce genetic variation into the hosts.
Ch. 27 Bacteria and Archaea
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Chapter 27 Bacteria & Archaea
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece.
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Chapter 27 Bacteria & Archaea.
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Topic 2.2 Prokaryotic Cells IB Biology Objectives Draw and Label a diagram of the ultrastructure of Escherichia coli as an example of a prokaryote.
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PROKARYOTES. THEY ARE EVERYWHERE The Major Similarities Between the Two Types of Cells (Prokaryote and eukaryote) Are: They both have DNA as their genetic.
Chapter 27: The Prokaryotes Objectives 1.Learn about the prokaryotic adaptations that make them successful, including the diverse metabolic pathways. 2.Learn.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Bacteria Staphylococcus bacteria in nose.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Section B1: The Structure, Function, and Reproduction of Prokaryotes 1.Nearly.
Prokaryotes Chapter 27. Found wherever there is life; thrive in habitats that are too cold, too hot, too salty, etc. Most live in symbiotic relationships.
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Regents Biology Monday, 12/8 Today’s Agenda: 1. Turn in HW (Cell Craft) 2. Go over Limits To Cell Size lab 3. Lecture on viruses and bacteria 4. Time.
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