cell envelope

• All cells are composed of protoplasm.
• Protoplasm (proto meaning “first” and plasm meaning “formed”)

  • an aqueous colloidal solution of carbohydrates, proteins, lipids, nucleic acids, and inorganic salts surrounded by a limiting cell membrane.
  • is predominantly water with organic compounds in a colloidal suspension and ​

  inorganic compounds in solution.
• nucleoplasm -the protoplasm inside the nucleus
• cytoplasm- the protoplasm outside the nucleus
• cytoplasm- the protoplasm outside the nucleus
• They tend to assume cubical, spherical, or cylindrical shapes, and have a cell membrane that encases an internal matrix called the cytoplasm.
• The majority of bacteria have a chemically

  complex external covering, termed the cell

  envelope, that encloses the cytoplasm
• Hans Christian Gram developed a staining technique, the Gram stain, which is commonly used to delineate two different groups of bacteria known as: 1. gram-positive bacteria and, 2. gram-negative bacteria.
• Cell wall - ​it helps determine the shape of a bacterium it also provides the kind of strong structural support necessary to keep a bacterium intact despite constant changes in environmental conditions
• The cell walls of most bacteria gain their relative strength and stability from a unique macromolecule ​called peptidoglycan (PG)
• The bulk of the gram-positive cell wall s a thick, homogeneous sheath of peptidoglycan ranging from 20 to 80 nm in thickness
• Gram positive - ​It also contains tightly bound acidic polysaccharides, including teichoic acid directly attached to the ​peptidoglycan and lipoteichoic

  acid
• Teichoic acid is a polymer of ribitol or glycerol a​nd phosphate embedded in the peptidoglycan

  sheath.
• Lipoteichoic acid is similar in structure but is ​attached to the lipids in the plasma membrane
• The cell wall of gram-positive

  bacteria is loosely adherent to the

  cell membrane, but at their junction

  lies a small compartment called the

  periplasmic space
• The gram-negative cell wall is more complex in morphology because it is composed of an outer membrane (OM) and a thinner shell of ​peptidoglycan
• The outer membrane is somewhat similar in construction to the cell membrane, except that it contains specialized types of lipopolysaccharides (LPS) and lipoproteins.
• Porins - regulatory control over molecules entering and leaving the cell.
• There is a well-developed periplasmic space above and below the peptidoglycan.
• periplasmic ​space in gram-negative bacteria is a ​site of many metabolic reactions related to synthesis and transport of proteins, actions of enzymes, and energy release.
• The outer membrane contributes an extra barrier in gram-negative bacteria thatmakes them more impervious to some antimicrobic chemicals such as dyes and disinfectants, so they are generally more difficult to inhibit or kill than are grampositive bacteria.
• NONTYPICAL CELL WALL

  ​Mycobacterium contains peptidoglycan and stain grampositive, but the bulk of their cell wall is composed of unique types of lipids.
• One of these is a very-long-chain

  fatty acid called mycolic acid, or

  cord factor, that contributes to

  the pathogenicity of this group.
• mycolic acid - are unique

  long chain fatty acids found

  in the lipid‐rich cell walls of

  mycobacteria
• GRAM-POSITIVE VS GRAM-NEGATIVE BACTERIA

  A) one

  B) two

  C) peptidoglycan

  D) teichoic acid

  E) lipoteichoic acid

  F) mycolic acids and polysaccharides

  G) lipopolysaccharides

  H) lipoprtotein

  I) peptidoglycan

  J) porin proteins

  K) thicker 20-80 nm

  L) thinner 8-11 nm

  M) no

  N) yes

  O) narrow

  P) extensive

  Q) more penetrable

  R) less penetrable

  
• Organelles – A small structure in a cell that is surrounded by a membrane and has a specific function.
• Organelles that are common to all eukaryotic cells are the

  nucleus, the mitochondria, the endoplasmic reticulum, ribosomes, the Golgi apparatus, and lysosomes.
• This property — the presence or absence of a nucleus — is used as the basis for a simple but fundamental

  classification of all living things.
• eukaryotes (from the Greek words eu, meaning “well” or “truly,” and karyon, a “kernel” or “nucleus”)

  • organisms whose cells have a nucleus

  e.g. Animals, Plants, Fungi, Protists
• prokaryotes (from pro, meaning “before”) - Organisms whose cells do not have a nucleus

  e.g. Archaea and Eubacteria
• Most prokaryotes live as single-celled organisms, although some join together to form chains, clusters, or other organized, multicellular structures
• Shape and Structure: prokaryotes may seem simple and limited
• Chemistry: are the most diverse class of cells on the

  planet
• Habitat: exploit an enormous range of habitats, from hot

  puddles of volcanic mud to the interiors of other living cells, and they vastly outnumber all eukaryotic organisms on Earth.
• aerobic - using oxygen to oxidize food molecules
• anaerobic - and are killed by the slightest

  exposure to oxygen.