Swimming of a bacterium towards a chemical is termed
Answer: A
Correct answer: positive chemotaxis
Movement towards a chemical is positive chemotaxis; movement away from a repellent is negative chemotaxis. Phototaxis is a response to light and magnetotaxis to a magnetic field.
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Chemically the capsule may be
Answer: C
Correct answer: either (a) or (b)
Most capsules are polysaccharide, but some are polypeptide - Bacillus anthracis has a capsule of poly-D-glutamic acid, whose D-amino acids resist degradation. Either kind resists phagocytosis, which is what makes capsulated strains the virulent ones.
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Peptidoglycan is found only in the bacterial
Answer: C
Correct answer: cell wall
Peptidoglycan is a structural polymer found only in the bacterial cell wall, where its cross-linked mesh resists the cell’s internal turgor pressure. The membrane is lipid, the glycocalyx is capsule and slime material, and the spore has its own distinctive cortex - which does contain a modified peptidoglycan, but the wall is where the polymer belongs.
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The cell walls of Gram positive bacteria contain two modified sugars, N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM). They are covalently linked by
Answer: D
Correct answer: β- 1,4-glycosidic bond
NAG and NAM alternate along the glycan backbone, joined by β-1,4-glycosidic bonds - the same linkage as in cellulose and chitin, and the one lysozyme hydrolyses. An α linkage, as in starch, would give a quite different, non-structural polymer.
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Which of the following organisms has sterols in its cytoplasmic membrane?
Answer: C
Correct answer: Mycoplasma
Mycoplasma is the exception among bacteria: having no cell wall, it strengthens its membrane with sterols taken up from the host. That is why it needs a sterol-containing medium to grow, and why it is naturally resistant to penicillin.
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Name the component of flagellum.
Answer: D
Correct answer: All of these
A bacterial flagellum has three parts: the filament, the long helical propeller of flagellin; the hook, a short curved coupling; and the basal body, the set of rings anchoring the motor in the membrane and wall.
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The location where the bacterial chromosome concentrates is called
Answer: C
Correct answer: nucleoid
The bacterial chromosome is concentrated in an irregular region called the nucleoid. It is not a nucleus: there is no membrane around it, so transcription and translation can proceed together.
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Which of the following is analogous to mesosomes of bacteria?
Answer: A
Correct answer: Mitochondria of eukaryotes
The mesosome is an infolding of the plasma membrane, long taken to be the site of the respiratory enzymes - hence the analogy with the mitochondrion. (Electron microscopy with better fixation suggests mesosomes are largely artefacts, but the comparison is the one the syllabus expects.)
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Which of the following has Chinese letter arrangement?
Answer: D
Correct answer: Corynebacterium diphtheriae
Corynebacterium diphtheriae divides by snapping fission, so the daughter cells swing apart but stay joined at one end, producing the V and L shapes described as a Chinese-letter arrangement.
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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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