A. In the Gram stain, a dye called crystal violet is used to stain the cells pur

Question

A. In the Gram stain, a dye called crystal violet is used to stain the cells purple. ive cells have thinner cell walls than Gram positive bacteria. B. a Gram negative C. In the Gram stain, alcohol is used to kill the bacteria D. Gram positive cells end up being stained purple E: Gram negative cells end up being stained pink or red. 31. The Gram stain divides microorganisms into two groups, purple vs. red, on the basis of differences in the: A. presence of a capsule. B. presence of an outer membrane. C. thickness of the peptidoglycan layer of the cell wall. D. presence of waxy mycolic acids in the cell wall. E. presence of endospores. 32. What is the correct order in which these reagents are used in the Gram stain A. Crystal Violet, Ethanol, lodine, Safranin, B. Crystal Violet, Safranin, Ethanol, lodine C. Crystal Violet, Iodine, Ethanol, Safranin D. Safranin, lodine, Crystal Violet, Ethanol E. lodine, Safranin, Ethanol, Crystal Violet 33. Volvox belongs to which of the following Kingdoms? a. Animalia b. Protista c. All answers are correct d. Fungi algac. 34. The Phacophyta are the A) blue-green B) brown C) green D) red E) yellow-green 35. The poisonous "red tides" result from blooms of A) diatoms B) dinoflagellates C) red algae D) foraminifera E) euglenoid 36. Organisms that move by means of pseudopodia belong to the group A) algae B) Sarcodina C) diatoms

Explanation / Answer

Ans 31: C) thickness of the peptidoglycan layer of the cell wall

The gram positive bacterias have a mesh work like thick peptidoglycan layer , due to which they retain the purple colour of crystal violet. This layer is just 10% of the cell envelope in gram negative bacterias so they aren't able to hold the crystal violet stain and are counter stained by safranin , and hence appear pink.

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