bacterial structure I and II - levinson Flashcards
what are the 5 major groups of organisms that cause human diseases?
bacteria fungi protozoa helminths viruses
what organisms are in the prokaryote kingdom?
bacteria
what organisms are in the protist kingdom?
fungi (yeasts and molds) and protozoa
what organisms are in the animal kingdom?
helminths (worms)
how can you distinguish protists from animals and plants?
protists are either unicellular or relatively simple microorganisms
which organisms are parasites?
helminths and protozoa
biological relationships of pathogenic microorganisms (table)- kingdom- pathogenic microorganisms- type of cells
- animals
- helminths
- eukaryotic cells
- protists
- protozoa and fungi
- eukaryotic cells
- prokaryotes
- bacteria
- prokaryotic - viruses
- noncellular
- bacteria
describe the structure of cells.
have a nucleus or nucleoid that contains DNA
nucleus surrounded by cytoplasm where proteins are synthesized and energy generated
describe the structure of viruses.
inner core of genetic material but no cytoplasm
depend on host cells to provide the machinery for protein synthesis and energy generation
how do eukaryotic cells replicate?
mitosis - one parent cell divides to make two progeny cells while retaining its cellular structure
how do prokaryotic cells replicate?
binary fission
how do viruses replicate?
disassemble produce many copies of their nucleic acid and protein
reassemble into multiple progeny
can bacteria replicate extracellularly?
most can, except rickettsiae and chlamydiae
what is the difference in nucleic acid between cells and viruses?
cells have both DNA and RNA viruses have DNA or RNA but not both
what are the defining characteristics of eukaryotic cells?
have a true nucleus with multiple chromosomes surrounded by a nuclear membraneuses mitotic apparatus to ensure equal allocation of chromosomes to progenycontain organelles (ie mitochondria and lysosomes) and ribosomes
what are the defining characteristics of prokaryotic cells?
nucleoid consists of a single cellular molecule of loosely organized DNA lacks nuclear membrane and mitotic apparatusno organelles and smaller ribosomesrigid external cell wall that contains peptidoglycan
what is peptidoglycan and what is it made of?
polymer of AA and sugars that makes up the rigid cell wall of most prokaryotes
what is the cell wall of eukaryotes like?
either have a flexible cell membrane or rigid wall of chitin (fungi)
what is chitin and what is made of?
makes up rigid cell wall of fungimade of a homopolymer of N-acetylglucosamine
what organisms have sterols?
eukaryotic cell membranes contain sterolsno prokaryotes except for mycoplasma do
which organisms are motile and which ones aren’t?
protozoa are motile, as are some bacteriafungi and viruses aren’t
what do protozoa use to move?
three different organs of locomotion: flagella, cilia and psuedo-pods
what do bacteria use to move?
flagella
how are microorganisms named?
bacteria, fungi, protozoa, and helminths are named according to binomial Linnean system (uses genus and species)
viruses aren’t
what are the different shapes of bacteria?
cocci = round bacilli = rods spirochetes = spiral-shaped pleomorphic = variable in shape
what determines the shape of bacterium?
its rigid cell wall
how do cocci bacteria vary in terms of arrangement?
can occur in pairs = diplococci
in chains = streptococci
grapelike clusters = staphylococci
what determines the arrangement of bacteria?
orientation and degree of attachment of the bacteria at the time of cell division
how large are bacteria?
range in size from about 0.2 to 5 umsmalles are the same size as the largest viruses
what is the outermost component of bacteria?
cell wall most commonlysome have capsule, flagella, and pili as well
what is the function of peptidoglycan in the bacterial cell wall?
provides structural support and maintains characteristic shape of cell
what factors are different between gram positive and gram negative bacteria? (general)
structure
chemical composition
thickness of cell wall
what are the layers of bacterial cell walls?
outer:flagellum, techolic acid, pilus if present capsule outer membrane in gram-negative peptidoglycan cytoplasmic membrane
how does the peptidoglycan layer vary between gram positive and gram negative bacteria?
much thicker in gram positive bacteria
many gram-positive
how does the outer layer of gram positive and gram negative bacteria differ?
gram negative have a complex outer layer of lipopolysaccharide, lipoprotein, and phospholipid
what is periplasmic space and which type of bacteria have it? what is found there?
in gram-negative bacteriabetween outer-membrane layer and cytoplasmic membrane
where beta-lactamase enzymes are in some species
what do beta-lactamase enzymes do? where would they be found?
enzymes that degrade penicillins and other beta-lactam drugs
in periplasmic space in gram-negative bacteria
what is endotoxin and where is it found?
in gram-negative bacteria
lipopolysaccharide
what are porin proteins and where are they found?
in the cell wall of both gram positive and gram negative bacteria
facilitate passage of small hydrophilic molecules into the cell
in gram-negative, allow entry of essential substances such as sugars, AA, vitamins, and metals and many antimicrobial drugs
what are acid-fast bacteria?
ones that can’t be gramstained
mycobacteria resist decoloratization with acid-alcohol after being stained with carbolfuchsindue to high concentration of lipids (mycolic acids) in the cell walls
what are mycolic acids? where are they found? how do they affect gram staining?
lipids found in high concentration in mycobacteria
prevent gramstaining
what are the three components of the bacterial cell wall (that they consider important)?
peptidoglycan
lipopolysaccharide
teichoic acid
what is peptidoglycan and where is it found?
complex, interwoven network that surrounds the entire cell and is composed of a single covalently linked macromolecule
found only in bacterial cell walls
what is the structural importance of peptidoglycan?
provides rigid support for the cell
maintains cell shape
allows cell to withstand media of low osmotic pressure (such as water)
what is peptidoglycan composed of (ie describe the carbohydrate backbone)?
alternating N-acetylmuramic acid and N-acetylglucosamine moleculestetrapeptide consisting of D- and L-amino acids is attached to each of the muramic acid molecules
what aspect of peptidoglycan varies between bacteria?
precise composition of tetrapeptide link attached to muramic acid
what is diaminopimelic acid a component of and what organism is it unique to?
unique to bacterial cell walls
component of carbohydrate backbone
what is D-alanine a component of and what does it do?
part of bacterial cell walls
involved in cross-links between the tetrapeptide and in the action of penicillin
what is different about the AA in the tetrapeptide in bacterial cell walls?
contain the D-isomers of AA
most proteins contain the L-isomers
what drugs target bacterial cell walls, and how?
penicillins, cephalosporins and vancomycininhibit the synthesis of peptidoglycan by inhibiting transpeptidase that makes the cross-links between two adjacent tetrapeptides
how would gram-negative and gram-positive bacteria appear after being stained?
gram-positive will stain blue
gram-negative will stain red
what are the steps in the gram stain procedure?
1: crystal violet dye stains all cells blue/purple
2: iodine solution is added - forms a crystal violet-iodine complex - all cells continue to appear blue
3: organic solvent (acetone or ethanol) extracts the blue dye complex from lipid-rich, thin-walled gram-negative bacteria to a greater degree than from thick-walled gram-positive bacteria
4: red dye safranin stains decolored gram-negative cells red/pink
how is the gram stain used clinically?
used to identify bacteria and choose antibacterial treatment
how do gram-negative bacteria versus gram-positive bacteria compare in terms of responsiveness to penicillin?
gram-positive are more susceptible
what is the sensitivity of the gram stain procedure?
very low because it requires about 100,000 bacteria/mL to see 1 bacterium per microscope field
therefore need to incubate patient’s blood
where is lysozyme found and what does it do to bacteria?
enzyme in human tears, mucus, saliva
cleaves peptidoglycan backbone by breaking glycosyl bonds
