Question

1. Select set of characteristics that are shared by every organism studied by microbiologists a) a prokaryote, a pathogen b) unicellular, eukaryote c) A and B d) neither A nor B is shared by every living organism studied by microbiologists 2. Gram positive and Gram negative bacteria are immersed in ocean water, You discover that minutes into these cells being immersed in ocean water the cells shrunk. You conclude thate ocean wate a) isotonic to the cytoplasms of each cell b) hypertonic to the cytoplasms of each cell c) hypotonic to the cytoplasms of each cell 3. The chemical analysis of envelopes isolated from cells revealed the presence of lipopolysaccharides. Select correct answer a) Envelopes of both cel types, A and B contain lipopolysaccharide b) Neither cell type A nor B contains lipopolysaccharide c) Cell A type contains lipopolysaccharide d) Cell B type contains lipopolysaccharide. 4. Red shapes, 1-7, circle either hydrophobic or a hydrophilic region of a macromolecule that is integral to (9 bacterial envelope. Choose a selection that lists jb88 hydrophobic regions a) 1, 2, 4, and 6 b) 3, 5, and 7 c) 2, 4, and 6 d) 3 and 5 Which of the following statements is the most accurate about Gram staining. a) Safranin differentially stains Gram negative cells b) Crystal violet difterentially stains Gram positive cells c) Acetone/alcohol differentially destains Gram negative cells d) Gram's iodine differentially stains Gram positive cells 5. 6. Every Gram negative bacterial cel a) has plasmids b) is the only type of bacteria with circular genomic DNA c) always has bacterial capsule d) A and C e) None of the answer choices apply to every Gram negative bacterial cell Bacterial flagellum is a) filamentous structure every bacterial cell has b) found only in Gram negative bacteria c) component of bacterial envelope d) Aand C e) B and C

Answer 1

1) The answer is (d)

This is because an organism may also be a eukaryote or a saprophyte or it may be multicellular or it may be a prokaryote. The possibilities of the microbe being of any category is limitless in Microbiology. Hence, neither A nor B will be common for every microorganism for a microbiologist.

2) The answer is (b)

The cells of both the bacteria shrunk. Hence, it indicates that the difference in the structure of their cell walls does not matter. And since the cells shrunk, it is clear that the components of the cytoplasm that are in the highest concentration pass to the water that has a lower concentration of solutes. Hypertonic or hypotonic is with respect to the water molecules. Hence, ocean water was hypertonic since it had more water molecules and less amount of salts than the inside of the cells.

3) The answer is (c)

Only cell type A contains the lipopolysaccharide layer. This is because the lipopolysaccharide is the outermost layer of the cell membrane in Gram negative bacteria and is absent in Gram positive bacteria. The figure demonstrated along side clearly shows the presence of 3 layers including the outermost layer only in the cell A and not in the cell B.

4) The answer is (c)

Only the regions marked as 2, 4 and 6 are hydrophobic. This is because these regions are present in or around the tail portion of the phospholipid bilayer. And it is known that the tail of such a layer is hydrophobic and not attracted towards water or extracellular fluid.

5) The answer is (b)

Crystal violet is the primary stain used in Gram staining procedures and hence the difference in the positive and negative bacteria is due to this stain. This stain contains iodine that gets trapped inside the large peptidoglycan layer of Gram positive bacteria and hence differentially stains only gram positive bacteria.

6) The answer is (d)

Every bacterial cell will possess a plasmid and a capsule as these are very essential for the survival of bacteria. Plasmid acts as the extra-chromosomal genetic material and the capsule helps the bacteria to survive the harsh unfavourable conditions.

7) The answer is (c)

This is because only the motile bacteria will posses a flagellum or a pilus and not all the bacteria. Moreover this is not a characteristic feature of Gram negative bacteria only. Hence, the right answer has to be that is a component of the envelope since it is used for the attachment of the bacteria to the substratum.