LE 2 - MICRO

Question 1

11. The cocci which mostly occur in single or pairs are
    a. Tetracocci
    b. Diplococci
    c. Streptococci
    d. None of the choices are correct

Answer 1

b. Diplococci

Tetracocci - five cocci adjusted together
Diplococci - two cocci adjusted together
Streptococci - series of cocci

Question 2

12. Which of the following may contain fimbriae?
    a. Gram Negative Bacteria only
    b. Gram Positive Bacteria
    c. Both Gram Negative and Gram Positive Bacteria
    d. None of the choices are correct

Answer 2

a. Gram Negative Bacteria only

Fimbriae are hair-like structures found on the surface of many Gram-negative bacteria. They are involved in the process of adhesion to host cells and are particularly important for bacteria that

Question 3

13. Cluster of flagella at one pole
    a. Lophotrichous
    b. Ampitrichous
    c. Peritrichous
    d. Monotrichous

Answer 3

a. Lophotrichous

Monotrichous - Single flagella at the end of the cell
Lopotrichous - Numerous/Cluster of flagella at one pole of the cell
Amphitrichous - Flagella at both pole of the cell Peritrichous - Flagella all over the cell surface

Question 4

Flagella move the cell by
a. Spinning like a propeller
b. An individual flagellum beating in a whip-like motion
c. Many flagella beating in a synchronous whip-like motion
d. Attaching to nearby particles and contracting

Answer 4

a. Spinning like a propeller

Flagella in bacteria move the cell by rotating like a propeller.

Question 5

The protein from which a hook and filaments of flagella are composed of, is
a. Peptidoglycan
b. Gelatin
c. Flagellin
d. Casein

Answer 5

c. Flagellin

Flagellin is the protein from which the hook and filaments of bacterial flagella are composed.

Question 6

Which may contain fimbriae?
a. Gram Positive
b. Gram Negative
c. Both
d. NOTA

Answer 6

b. Gram Negative

Fimbriae are primarily found on Gram-negative bacteria and are involved in the process of adhesion to host cells.

Question 7

Bacteria without flagella are unable to
a. Move
b. Reproduce
c. Attach
d. NOTA

Answer 7

a. Move

Question 7

Peptidoglycan content of Gram positive bacteria?
a. 50%
b. 11+0.22%
c. About 20%
d. About 10%

Answer 7

a. 50%

Gram-positive bacteria typically have a thick peptidoglycan layer, which can constitute up to 50% of the wall material. The substantial peptidoglycan layer in Gram-positive bacteria is in contrast to Gram-negative bacteria, which have a thinner peptidoglycan layer located between the inner and outer membranes. This difference in peptidoglycan content and structure is a key factor in the Gram staining process, which distinguishes between the two types of bacterial cell walls.

Question 8

True about gram positive bacteria
a. Thicker wall than gram negative
b. Has many cell layers
c. Contains Teichoic Acid
d. AOTA

Answer 8

d. AOTA (All of the Above)

a. Thicker wall than gram negative - True. Gram-positive bacteria have a thicker peptidoglycan layer than gram-negative bacteria.

b. Has many cell layers - This can be misleading. Gram-positive bacteria have a thick layer of peptidoglycan, but it doesn’t mean they have “many cell layers” like in a eukaryotic context. However, the thick peptidoglycan layer might be referred to as “many layers” of peptidoglycan.

c. Contains Teichoic Acid - True. Teichoic acids are polymers of glycerol or ribitol joined by phosphate groups, and they are present in the cell walls of many gram-positive bacteria.

Question 9

Cell wall of gram negative bacteria can easily be destroyed by
a. Lysozyme
b. Lipase
c. Pectinase
d. Peroxidase

Answer 9

a. Lysozyme

Lysozyme is an enzyme that breaks down the peptidoglycan layer in bacterial cell walls. While it is more effective against Gram-positive bacteria because they have a thicker peptidoglycan layer, it can also affect the thinner peptidoglycan layer of Gram-negative bacteria. However, the outer membrane of Gram-negative bacteria provides some protection against lysozyme. Nonetheless, among the options provided, lysozyme is the enzyme most directly involved in damaging bacterial cell walls.

Question 10

Peptidoglycan provides structural strength to bacterial cell walls. This is made of polysaccharide and peptide chains and was formerly known as:
A. N-Acetylglucosamine
B. Murein
C. N- Acetylmuramic Acid
D. Dipropionic Acid

Answer 10

B. Murein
Peptidoglycan, which provides structural strength to bacterial cell walls, was formerly known as murein.

Question 11

What drug targets 30 S ribosomal subunits?
A. Chloramphenicol
B. Tetracycline
C. Clindamycin
D. None of the above

Answer 11

B. Tetracycline
Tetracycline targets the 30S ribosomal subunit in bacteria, inhibiting protein synthesis.

Question 12

31. The last step in synthesis of peptidoglycan
    a. Attaching to amino acids to form a cross-link
    b. Binding of Penicillin to a membrane protein
    c. Attachment of a peptide to muramic acid
    d. Attachment of a portion of peptidoglycan to amembrane protein

Answer 12

a. Attaching to amino acids to form a cross-link

This cross-linking of peptide chains provides the structural rigidity to the peptidoglycan layer. The enzyme that facilitates this reaction is transpeptidase. Penicillin and related antibiotics exert their effect by inhibiting this enzyme, preventing the formation of the cross-links and thus compromising the integrity of the bacterial cell wall.

Question 13

What is most likely to be exposed on the surface of gram negative bacterium?
a. Pore protein (porin)
b. Phospholipids
c. Protein involved in energy generation
d. Lipoteichoic Acid

Answer 13

a. Pore protein (porin)

Gram-negative bacteria have an outer membrane that contains specific channel-forming proteins known as porins. These porins allow the passive diffusion of small hydrophilic molecules. Lipoteichoic Acid, on the other hand, is associated with the cell walls of Gram-positive bacteria and not Gram-negative bacteria.

Question 14

The cell wall of:
a. Gram-positive bacteria is thicker than Gram-negative bacteria
b. Gram-negative bacteria is thicker than Gram-positive bacteria
c. Gram-positive and Gram-negative have the same thickness but difference composition
d. None of the above

Answer 14

a. Gram-positive bacteria is thicker than Gram-negative bacteria

Question 15

Structural difference of bacteria from archaea is on:
a. Ribosome
b. Nucleus
c. Cell wall
d. Cytoplasm

Answer 15

c. Cell wall

One of the key structural differences between bacteria and archaea is in the composition of their cell walls. Bacterial cell walls primarily contain peptidoglycan, whereas archaeal cell walls do not. Instead, archaea may have cell walls made up of pseudopeptidoglycan, glycoproteins, or other unique components. This difference in cell wall composition is one of the main distinguishing features between these two domains of prokaryotes.

Question 16

41. Microbial growth can be inhibited by:
    a. Temperature
    b. Moisture control
    c. Antimicrobial chemicals
    d. All of the above

Answer 16

d. All of the above

All the options listed can inhibit microbial growth:

a. Temperature: Both high and low temperatures can inhibit microbial growth. High temperatures (as in cooking or boiling) can kill many microbes, while refrigeration can slow down the growth of many bacteria.

b. Moisture control: Many bacteria require moisture to grow. Drying or desiccation can inhibit bacterial growth, which is why foods like jerky or dried fruits have a longer shelf life.

c. Antimicrobial chemicals: These can kill or inhibit the growth of bacteria. Examples include disinfectants, antiseptics, and antibiotics.