Bacteria Morphology Questions and Answers

Q: The other name for peptidoglycan is

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.

Q: The protein of which the hook and filament of a flagellum are composed is

Correct answer: flagellinThe 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.

Q: Surface area/volume ratio of bacteria is exceedingly low compared to the same ratio for larger organisms of similar shape.

Correct answer: FalseThe 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.

Q: The crosswalls constrict which of the following parts and then grow inwards to form septum?

Correct answer: plasmalemmaSeptum 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.

Q: Bacteria having no flagella are unable to

Correct answer: moveFlagella 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.)

Q: The common word for bacteria which are helically curved rods is

Correct answer: spirillaSpirilla 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.

Q: Peptidoglycan is also known as

Correct answer: murein mucopeptidePeptidoglycan 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.

Q: What is the approximate size of the bacterial cell?

Correct answer: 0.5 to 1.0 micrometer in diameterA 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.

Q: Polyisoprenoid branched-chain lipids are present in which of the following?

Correct answer: ArchaebacteriaArchaea have membranes quite unlike anyone else’s: branched polyisoprenoid chains linked to glycerol by ether bonds rather than the straight fatty acids and ester bonds of bacteria and eukaryotes. Ether bonds and branched chains are far more stable, which is part of how the extreme thermophiles and acidophiles among them survive.

101.

Porins are located in

A.the outer membrane of gram-negative bacteria
B.the peptidoglycan layer of gram-positive bacteria
C.the cytoplasmic membrane of both gram-negative and gram-positive bacteria
D.the periplasmic space of gram-negative bacteria

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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102.

The other name for peptidoglycan is

A.mucopeptide
B.murein
C.both (a) & (b)
D.none of these

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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103.

The protein of which the hook and filament of a flagellum are composed is

A.keratin
B.flagellin
C.gelatin
D.casein

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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104.

Surface area/volume ratio of bacteria is exceedingly low compared to the same ratio for larger organisms of similar shape.

A.True
B.False
C.May be
D.Can't say

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.

Discuss in Forum

105.

The crosswalls constrict which of the following parts and then grow inwards to form septum?

A.hyphae
B.lumen
C.protoplasm
D.plasmalemma

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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106.

Bacteria having no flagella are unable to

A.move
B.reproduce
C.stick to tissue surfaces
D.grow in nutrient agar

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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107.

The common word for bacteria which are helically curved rods is

A.cocci
B.pleomorphic
C.bacillus
D.spirilla

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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108.

Peptidoglycan is also known as

A.N-acetyl muramic acid
B.murein mucopeptide
C.N acetylglucosamine
D.meso-diaminopimelic acid

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.

Discuss in Forum

109.

What is the approximate size of the bacterial cell?

A.2mm in diameter
B.1mm in diameter
C.2 micrometer in diameter
D.0.5 to 1.0 micrometer in diameter

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.

Discuss in Forum

110.

Polyisoprenoid branched-chain lipids are present in which of the following?

A.Archaebacteria
B.Eubacteria
C.Archaebacteria and Eubacteria
D.Cannot be determined

Answer: A

Correct answer: Archaebacteria

Archaea have membranes quite unlike anyone else’s: branched polyisoprenoid chains linked to glycerol by ether bonds rather than the straight fatty acids and ester bonds of bacteria and eukaryotes. Ether bonds and branched chains are far more stable, which is part of how the extreme thermophiles and acidophiles among them survive.

Discuss in Forum

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