BLG 151 - Chapter 3 - Cell Structure and Function.docx

BLG 151 - Chapter 3 - Cell Structure and Function.docx -...

Info icon This preview shows pages 1–3. Sign up to view the full content.

Chapter 3 Cell Structure and Function 3.0 Bacterial Shapes, Arrangements and Sizes Shape: Arrangements: Name of Cocci Arrangements Name of Bacilli/ Spirochete Arrangements (Rigid helices) (Flexible helices) Two other shapes of bacteria are mycelium and pleomorphic: o mycelium – network of long, multinucleate filaments o pleomorphic – organisms that are variable in shape The size of bacteria varies from 0.3 μm to 600 x 80 μm. Why are bacteria so small? Bacteria are so small in size because their small size is necessary for sufficient nutrient uptake and protective mechanisms from predation. o Bacteria have limited organelles, so if they were to grow bigger, there would be empty space and this empty space would take up energy and lower the efficiency of their system 3.1 Bacterial Structure Inclusions – storage of carbon, phosphate, and other substances Gas vacuole – an inclusion that provides buoyancy for floating in aquatic environments Periplasmic space – In typical Gram-negative bacteria: contains hydrolytic enzymes and binding proteins for nutrient processing and uptake; in typical Gram-positive bacteria, may be smaller or absent Capsules and slime layers – resistance to phagocytosis, adherence to surfaces Fimbriae and pili – attachment to surfaces, bacterial conjugation and transformation, twitching and gliding motility Flagella – swimming and swarming motility
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

Endospore – allows survival under harsh environmental conditions NOTE: not all bacterial cells have flagella and/or fimbriae 3.2 How We Study Cell Parts: Cell Envelope – Exploring the Cell Wall A cell wall is a rigid structure that lies just outside the cell plasma membrane and is composed of peptidoglycan (Murein) o The peptidoglycan structure consists of 2 alternating sugars: N -acetylglucosamine (NAG) and N - acetylmuramic acid (NAM) Cells that lose their cell wall can survive in isotonic environments – an environment having the same osmotic pressure as the plasma membrane (note: the plasma membrane evolves its osmotic pressure resistance) Cell walls differentiate two types of bacteria: 1. Gram-positive: stain purple; think peptidoglycan Composed of mainly peptidoglycan, but also contains teichoic acids , which are negatively charged. Teichoic acids help: Maintain the cell envelope Protect the cell envelope from environmental substances Bind to host cells Some gram-positive bacteria also have a layer of proteins on the surface of peptidoglycan: S-layer and capsule Gram-positive bacteria also have smaller periplasmic space (space between plasma membrane and cell wall) than gram-negative bacteria 2. Gram-negative: stain pink or red; thin peptidoglycan and outer membrane More complex than Gram-positive Does not have teichoic acids Consist of a thin layer of peptidoglycan enclosed by an inner and outer membrane, whereby the outer membrane is composed of lipids, lipoproteins,
Image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.
  • Fall '09

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern