BIOD171 LAB MICROBIOLOGY Module 3 Final Exam Review Q & A 2026 (Complete And Verified Study material) (22pages) LEARNEXAMS

1. What is the primary purpose of Gram staining in microbiology? A. To identify bacteria based on cell wall composition B. To assess the size of bacterial colonies C. To determine the virulence of a bacterium D. To count the number of bacterial cells Answer: A. The primary purpose of Gram staining is to differentiate bacterial species into two large groups (Gram-positive and Gramnegative) based on the chemical and physical properties of their cell walls. 2. Which of the following is a characteristic of Gram-positive bacteria after Gram staining? A. Pink coloration B. Purple coloration C. Colorless appearance D. Green coloration Answer: B. Gram-positive bacteria retain the crystal violet stain used in the process, resulting in a purple coloration. 3. During the Gram staining procedure, what is the role of iodine? A. It acts as a decolorizer B. It serves as a counterstain C. It functions as a mordant D. It is used as a primary stain Answer: C. Iodine acts as a mordant, forming a complex with the crystal violet stain, which helps the stain to adhere better to the bacterial cell wall. 4. What is the consequence of over-decolorization during the Gram staining process? A. Gram-positive cells may appear Gram-negative B. Gram-negative cells may appear Gram-positive C. Bacterial cells may be destroyed D. No staining will occur Answer: A. Over-decolorization can remove the crystal violet-iodine complex from Gram-positive cells, causing them to appear Gramnegative. 5. Which component of the bacterial cell wall primarily determines the