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GBBE Final Exam With Complete Solution
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GBBE Final Exam With CompleteSolution
Gram-positive bacteria - ANSWER Bacteria with thick peptidoglycan cell wall,
with no outer membrane. Teichoic acid in the cell wall/ regulates the
movement of positive ions. They stain very dark / purple in Gram stain.
Gram-negative bacteria - ANSWER The bacteria that have complex cell walls
with less peptidoglycan but with lipopolysaccharides. They stain pink very
brightly in Gram stain.
Safranin stain - ANSWER Added as the counter/secondary stain in a Gram
Stain which color the gram negative bacteria pink-red and have no effect on
gram positive bacteria.
Endotoxin - ANSWER A toxic component of the outer membrane of certain
gram-negative bacteria that is released only when the bacteria die.
Exotoxin - ANSWER A poisonous protein produced and secreted by an
actively growing prokaryote or other pathogen and that elicits specific
symptoms even if the disease-causing agent has been eliminated.
What is a mordant? - ANSWER a substance, usually an inorganic oxide, that
,combines with a dye or stain and fixes it in a material.
(for ex. iodine)
Purpose of iodine - ANSWER binds to primary stain and allows for
substance to become trapped in the cell wall
Three primary shapes of bacteria - ANSWER cocci, bacillus, spiral
Capsule - ANSWER Protects cell, makes it more virulent
Pilus - ANSWER short hair-like structures on cell surface (help w/ adherence
to structures and movement)
peptidoglycan - ANSWER A protein-carbohydrate molecule that gives
rigidity to the cell walls of bacteria; two monosaccharide units-NAG and
NAM makeup
Plasma membrane - ANSWER A selectively-permeable phospholipid bilayer
constituting the boundary of the cells
Primary chromosome - ANSWER circular DNA molecules in bacteria
, Plasmid - ANSWER small, extrachromosomal DNA molecule within a cell
which is physically separated from chromosomal DNA
Fimbriae - long filamentous polymeric protein structures at the surface of
bacterial cells; allow the bacteria to adhere to specific receptor
structures/colonise surfaces
Slime layer - a glycocalyx unorganized and loosely attached to the cell wall
Starch hydrolysis test- ANSWER iodine is added to agar. if starch is present,
forms a dark brown color. Hydrolysis of starch will create a clear zone around
the bacterial growth.
Motility test- ANSWER Non-motile- sharp and defined line, motile- swim
away from stab line, is not concentrated to line of inoculation
MacConkey test-ANSWER gram positive cannot grow, when it ferments
lactose-rends acidic, red, when doesn't ferment lactose-stays colorless
Catalase test-ANSWER all bacteria that undergo aerobic respiration (produce
hydrogen peroxide) are catalase-positive bubbles are produced
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