This set of Cell Biology Multiple Choice Questions & Answers (MCQs) focuses on “Extracellular Matrix and Cell Interactions – Cell Walls”.
1. Who discovered cell wall?
a) Karl Rudolphi
b) Boveri
c) J Rhodin
d) Van Beneden
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Explanation: Robert Hooke in the year 1665 observed a component of cell called the “wall” which surrounds the cell. Karl Rudolphi and JHF Link found the component independent cell wall in the year 1804.
2. What organism lacks cell wall?
a) Plant cells
b) Protozoa
c) Bacterial cells
d) Algae
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Explanation: The animal cells and the protozoa lacks cell wall. They only contain cell membrane followed by the cytoplasm. Because of this they do not have a rigid shape.
3. Bacteria can be divided into classes namely gram-positive bacteria and gram-negative bacteria based on their cell wall.
a) True
b) False
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Explanation: The bacteria are divided into gram positive and negative bacteria based on the thickness of the peptidoglycan present in their cell wall. The thick peptidoglycan layer is gram-positive cell wall and thin layer of peptidoglycan is gram-negative cell wall.
4. Which component is present in the cell wall of fungi?
a) Cellulose
b) Hemicellulose
c) Chitin
d) Pectin
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Explanation: The fungi have a cell wall made of chitin, which is a glycosamine polymer. Chitin has similar functions with the protein keratin. It is structurally similar to the polysaccharide cellulose.
5. What is S- layer?
a) Solid layer
b) Surface layer
c) Secondary layer
d) Soluble layer
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Explanation: The S-layer is otherwise known as a surface layer. It is present in the cell wall of most of the archaea bacteria. This layer is composed of proteins and glycoproteins. They are about a thickness of 5 to 25nm.
6. The cell wall of diatoms composed of __________
a) Biogenic alumina
b) Biogenic ammonia
c) Biogenic silica
d) Biogenic magnesia
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Explanation: The cell walls of marine diatoms have biogenic silica which is otherwise known as biogenic opal. This is found as small scales, granules or other geometric structures on the cell wall. This biogenic silica is a major contribution to the global carbon cycle.
7. Which of the following bacteria lacks cell wall?
a) Mycoplasma pneumoniae
b) Bacillus subtilis
c) Staphylococcus aureus
d) Helicobacter pylori
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Explanation: Mycoplasma is a genus of bacteria that does not have a distinct cell wall over their cell membrane. Even though these bacteria lack cell wall, they can effectively protect themselves against antibiotics which have a mode of action of inhibiting cell wall synthesis.
8. What is present in the cell wall of Mycobacterium tuberculosis?
a) Cellulose
b) Nitric acid
c) Acetone
d) Mycolic acid
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Explanation: Mycolic acid is present in the cell wall of Mycobacterium tuberculosis. It was first isolated from this species in the year 1938 by Stodola et al. Mycolic acid helps this organism to prevent itself from chemical attacks and dehydration.
9. Which of the following antibiotics have their mode of action of inhibition of cell wall synthesis?
a) Nalidixic acid
b) Ciprofloxacin
c) β-lactams
d) Norfloxacin
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Explanation: β-lactams is one of the antibiotics, which helps in destroying the bacteria by the inhibition of cell wall synthesis. This helps in the prevention of peptidoglycan synthesis.
10. Which of the following cell wall component can effectively defend against lysozyme?
a) Peptidoglycan
b) Pseudomurein
c) Chitin
d) Biogenic opal
View Answer
Explanation: Pseudomurein otherwise known as pseudopeptidoglycan is one of the cell wall components of archaea bacteria. They resemble peptidoglycan layer in function and structure but differ in chemical composition. Lysozyme is a defense mechanism in higher animals and they cannot defend against bacteria containing pseudomurein cell wall.
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