Which of the following may contain fimbriae?
Answer: B
Correct answer: Gram-negative bacteria
Fimbriae are short hair-like appendages used for attachment, and they are characteristic of gram-negative bacteria, where they are anchored in the outer membrane. They are not organs of motility - that is the flagellum - but they are important in colonisation and virulence.
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Porins are located in
Answer: A
Correct answer: the outer membrane of gram-negative bacteria
Porins are trimeric barrel proteins spanning the outer membrane, forming water-filled channels through which small hydrophilic molecules diffuse. They are the reason the outer membrane is a selective barrier rather than an impermeable one - and why large antibiotics, which cannot pass the pores, are so often ineffective against gram-negative bacteria.
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The other name for peptidoglycan is
Answer: C
Correct answer: both (a) & (b)
Peptidoglycan is called murein, from the Latin for a wall, and also mucopeptide - both names for the same cross-linked polymer of sugars and short peptides.
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The protein of which the hook and filament of a flagellum are composed is
Answer: B
Correct answer: flagellin
The filament and hook are built from flagellin, a globular protein that self-assembles into a hollow helical tube. Subunits travel up the hollow core and add themselves at the tip, so the flagellum grows from its far end.
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Surface area/volume ratio of bacteria is exceedingly low compared to the same ratio for larger organisms of similar shape.
Answer: B
Correct answer: False
The opposite is true: because surface area falls with the square of the linear dimension and volume with the cube, a very small cell has an exceedingly high surface-to-volume ratio. That is the central advantage of being small - a large membrane area serving a small cytoplasm allows rapid uptake of nutrients and rapid growth.
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The crosswalls constrict which of the following parts and then grow inwards to form septum?
Answer: D
Correct answer: plasmalemma
Septum formation begins with a ring of new wall material growing inwards from the existing wall. As it advances it constricts the plasmalemma, drawing the membrane in with it until the cross-wall is complete - usually leaving a central pore.
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Bacteria having no flagella are unable to
Answer: A
Correct answer: move
Flagella are the organelles of motility, so a bacterium without them cannot swim. It can still reproduce, grow on agar, and adhere - adhesion being the work of fimbriae. (Some non-flagellated bacteria do move by gliding or twitching, but not by swimming.)
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The common word for bacteria which are helically curved rods is
Answer: D
Correct answer: spirilla
Spirilla are rigid helically curved rods, moved by polar flagella. Spirochaetes are the flexible helical forms, driven by internal axial filaments; cocci are spherical and bacilli straight rods.
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Peptidoglycan is also known as
Answer: B
Correct answer: murein mucopeptide
Peptidoglycan is also called murein (from murus, a wall) or murein mucopeptide. NAM and NAG are its two sugars, and diaminopimelic acid one of the amino acids of its peptide side chains - components rather than alternative names for the polymer.
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What is the approximate size of the bacterial cell?
Answer: D
Correct answer: 0.5 to 1.0 micrometer in diameter
A typical bacterium is about 0.5-1.0 μm across and a few micrometres long - small enough to need a light microscope at its limit, or an electron microscope for detail. The small size gives a very high surface-to-volume ratio, which is what allows such rapid exchange with the environment and such fast growth.
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