What are the dimensions of the filaments that the thallus of a fungus consists of?
Answer: B
Correct answer: 5 to 10 micrometre
A hypha is typically 5-10 μm across, though it may be metres long. The thallus, or mycelium, is the whole mass of such filaments - a shape that gives an enormous surface area for absorbing nutrients.
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Which group of bacteria among the following have the largest area of contact?
Answer: B
Correct answer: Trichomes
A trichome is a chain in which the cells are in broad contact along their whole adjacent walls, so the filament behaves almost as a single organism - the arrangement in many cyanobacteria. In a streptobacillus or a palisade the cells touch only at their ends or along one face.
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The L Ring in a Gram-Negative bacterium flagella is associated with_________
Answer: B
Correct answer: Outer Membrane
The gram-negative basal body has four rings, and the letters name where each sits: L in the outer membrane (L for lipopolysaccharide), P in the peptidoglycan, and S and M at the cytoplasmic membrane. Gram-positive cells, having no outer membrane, have only the S and M rings.
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Which of these is a cocci occurring in single or pairs?
Answer: A
Correct answer: Diplococci
Diplococci divide in one plane and stay attached in pairs - Neisseria and Streptococcus pneumoniae are the familiar examples. Streptococci form chains, tetracocci groups of four, and staphylococci irregular clusters; the pattern follows from the planes of division and whether the cells separate.
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Which eukaryotic organelle is regarded as analogous to the mesosomes of bacteria?
Answer: C
Correct answer: Mitochondria of eukaryotes
The mesosome is an infolding of the bacterial plasma membrane, and it was long regarded as the site of respiratory enzymes - hence the analogy with the mitochondrion, which does that job in eukaryotes. (Modern work suggests mesosomes are largely artefacts of chemical fixation, but the comparison is the one textbooks and examinations use.)
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Flagella in bacteria enable them to
Answer: B
Correct answer: locomote
Flagella are organs of motility: the filament is turned like a propeller by a motor in the membrane, driven by the proton-motive force. Adhesion is the work of fimbriae and pili, and reproduction has nothing to do with flagella.
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Hyphal wall consists of microfibrils composed of ___________________
Answer: A
Correct answer: hemicellulose or chitin
A fungal wall is built of microfibrils in a matrix, and in most fungi the fibrillar material is chitin - a polymer of N-acetylglucosamine - with hemicellulosic glucans in the matrix. Cellulose walls occur only in the oomycetes. Note that this is quite unlike a bacterial wall, which is peptidoglycan, and is why antifungal drugs need different targets.
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What is a cluster of polar flagella called?
Answer: D
Correct answer: Lophotrichous
The prefixes describe the arrangement: lophotrichous is a tuft of several flagella at one pole; monotrichous a single one; amphitrichous flagella at both poles; peritrichous flagella all over the surface.
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The common word for bacteria which are straight rods is
Answer: B
Correct answer: bacilli
Bacilli are straight rods - note that the word is used both for the shape and for the genus Bacillus. Cocci are spherical, spirilla helical, and pleomorphic organisms have no fixed shape.
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The yeast cell or mould filament is surrounded by a true cell wall.
Answer: A
Correct answer: True
Both have a true, rigid cell wall, built mainly of chitin and glucans - not the peptidoglycan of bacteria, nor the cellulose of plants. It is what gives the yeast cell and the hypha their shape and resistance to osmotic pressure.
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