3) A large cluster (more than 8) of bacillus bacteria is called: a) coccus b) streptococcus c) staphylococcus d) octa bacillus e) none of the above 14) A streptobacillus shaped bacteria have the following shape/sructure: a) long chain of capsule/rodshaped cells b) long chain of spherical-shaped cells c) a single spherical-shaped cell d) a single capsule/rod-shaped cell e) none of the above. 15) If you are a passenger on the “Magic School Bus” and you want to “explore” the cytoplasmic component of a Gram -ve bacteria, you will have to go through: a) two membranes separated by periplasm and thick peptidoglycan region b) two membranes separated by periplasm and thin peptidoglycan region c) A glycocalyx and a membrane separated by a thin peptidoglycan region d) a thin peptidoglycan region & one membrane e) a thick peptidoglycan region & one membrane 16) If you are a passenger on the “Magic School Bus” and you want to “explore” the cytoplasmic component of a Gram +ve bacteria, you will have to go through: a) two membranes separated by periplasm and thick peptidoglycan region b) two membranes separated by periplasm and thin peptidoglycan region c) A glycocalyx and a membrane separated by a thin peptidoglycan region d) a thin peptidoglycan region & one membrane e) a thick peptidoglycan region & one membrane 17) The peptidoglycan layers are anchored to the cell membrane by: a) tetrapeptide chain b) dipeptide molecule c) teichoic acid d) lipoteichoic acid e) c & d 18) The peptidoglycan region in Gram +Ve bacteria is strengthened with ___ cross bridges of: a) Lipopolysaccahride b) Archaeol c) Hopanoids d) Polypeptides e) FtsZ 19) The fluid or region present between the inner membrane and the outer membrane of some bacteria is called: a) periplasm b) ectoplasm c) circumplasm d) lophoplasm e) amphiplasm
Added by Khalif P.
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Step 1: "Strepto-/staphylo-" describe arrangements of spherical cells (cocci); bacillus = rod-shaped and doesn't form a standard "large cluster" name among the options. Show more…
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The food poisoning bacterium Clostridium perfrin gens makes a toxin that binds to members of the claudin family of proteins, which are the main constituents of tight junctions. When bound to a claudin, the C-terminus of the toxin allows the N-terminus to insert into the adjacent cell membrane, forming holes that kill the cell. The portion of the toxin that binds to the claudins has proven to be a valuable reagent for investigating the properties of tight junctions. MDCK cells are a common choice for studies of tight junctions because they can form an intact epithelial sheet with high transepithelial resistance. MDCK cells express two claudins: claudin-1, which is not bound by the toxin, and claudin-4, which is. When an intact MDCK epithelial sheet is incubated with the C-terminal toxin fragment, claudin-4 disappears. becoming undetectable within 24 hours, In the absence of claudin- 4 , the cells remain healthy and the epithelial sheet appears intact. The mean number of strands in the tight junctions that link the cells also decreases over 24 hours from about four to about two, and they are less highly branched. A functional assay for the integrity of the tight junctions shows that transepithelial resistance decreases dramatically in the presence of the toxin, but the resistance can be restored by washing it out (Figure $Q 19-2 A$ ). Curiousily, the toxin produces these effects only when it is added to the basolateral side of the sheet; it has no effect when added to the apical surface (Figure $Q 19-2 B$ ). A. How can it be that two tight junction strands remain, even though all of the claudin-4 has disappeared? B. How do you suppose the toxin fragment causes the tight junction strands to disintegrate? C. Why do you suppose the toxin works when it is added to the basolateral side of the epithelial sheet, but not when added to the apical side?
The food-poisoning bacterium Clostridium perfringens makes a toxin that binds to members of the clau-din family of proteins, which are the main constituents of tight junctions. When the C-terminus of the toxin is bound to a claudin, the N-terminus can insert into the adjacent cell membrane, forming holes that kill the cell. The portion of the toxin that binds to the claudins has proven to be a valuable reagent for investigating the properties of tight junctions. MDCK cells are a common choice for studies of tight junctions because they can form an intact epithelial sheet with high transepithelial resistance. MDCK cells express two claudins: claudin-1, which is not bound by the toxin, and claudin-4, which is. When an intact MDCK epithelial sheet is incubated with the C-terminal toxin fragment, claudin-4 disappears, becoming undetectable within 24 hours. In the absence of claudin-4, the cells remain healthy and the epithelial sheet appears intact. The mean number of strands in the tight junctions that link the cells also decreases over 24 hours from about four to about two, and they are less highly branched. A functional assay for the integrity of the tight junctions shows that transepithelial resistance decreases dramatically in the presence of the toxin, but the resistance can be restored by washing out the toxin (Figure $Q 19-2 A$ ). Curiously, the toxin produces these effects only when it is added to the basolateral side of the sheet; it has no effect when added to the apical surface (Figure $Q 19-2 B$ ). A. How can it be that two tight-junction strands remain, even though all of the claudin-4 has disappeared? B. Why do you suppose the toxin works when it is added to the basolateral side of the epithelial sheet, but not when added to the apical side?
Three basic prokaryotic categories are cocci, spirilli, and bacilli. Describe the basic structural features of each category. a. These three prokaryote groups have similar basic structural features. They typically have cell walls enclosing nuclear membranes, cytoplasm, ribosomes, mitochondria and nucleoid region with genetic material. They may have a protective capsule, flagellum, pili and plasmids. b. Cocci and spirilli have similar basic structural features. They typically have cell walls enclosing cell membranes, a flagellum for locomotion and pili for attachment. Bacilli are rod shaped which contain ribosomes and a nucleoid region with genetic material. c. These three prokaryote groups have similar basic structural features. They typically have cell walls enclosing cell membranes, cytoplasm, ribosomes and a nucleoid region with chromosomes. They may have a protective capsule, flagellum, pili and plasmids. d. Bacilli and spirilli have similar basic structural features. They typically have cell walls enclosing nuclear membranes, a flagellum for locomotion and pili for attachment. Cocci are spherical containing ribosomes and a nucleoid region with genetic material.
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