BIOL 3201 LAB EXAM 1 QUESTIONS ANSWERED CORRECTLY LATEST UPDATE 2026
Primary stain - Answers Crystal violet
Mordant - Answers Gram's iodine
Decolorizer - Answers 95% ethanol
Counterstain - Answers Safranin
Gram-positive color - Answers Purple
Gram-negative color - Answers Pink/red
Gram-positive cell wall - Answers Thick peptidoglycan
Gram-negative cell wall - Answers Thin peptidoglycan + outer membrane
Function of mordant - Answers Forms CV-I complex
Function of decolorizer - Answers Removes stain from Gram-negative
Heat fixing purpose - Answers Kills cells and adheres cells to slide
Total magnification - Answers Ocular × objective
100× objective requires - Answers Immersion oil
Oil function - Answers Reduces refraction and increases resolution
Resolution - Answers Ability to distinguish two close objects
Parfocal - Answers Image stays in focus when switching objectives
Coarse focus use - Answers 4× and 10× only
Fine focus use - Answers 40× and 100×
Bacteria appear transparent because - Answers ~80% water
Phase contrast microscope - Answers Used to view internal structures without stain
Reagent for catalase test - Answers Hydrogen peroxide
Positive result for catalase test - Answers Bubbles
Negative result for catalase test - Answers No bubbles
Function of catalase - Answers Breaks down hydrogen peroxide
Detects in oxidase test - Answers Cytochrome c oxidase
Positive result for oxidase test - Answers Blue/purple within 30 seconds
Negative result for oxidase test - Answers No color change
Positive result for KOH test - Answers Strings form → Gram-negative
Negative result for KOH test - Answers No strings → Gram-positive
Purpose of KOH test - Answers Verify Gram stain
Red after reagents A & B in nitrate reduction - Answers Nitrate → nitrite (positive)
No color after A & B in nitrate reduction - Answers Add zinc
Clear zone in starch hydrolysis - Answers Positive (starch hydrolyzed)
Dark plate in starch hydrolysis - Answers Negative
Reagent for coagulase test - Answers Plasma
Clot formation in coagulase test - Answers Positive
No clot in coagulase test - Answers Negative
Used to identify in coagulase test - Answers Staphylococcus aureus
Yellow in phenol red carbohydrate broth - Answers Acid (fermentation)
Bubble in phenol red carbohydrate broth - Answers Gas production
Red in phenol red carbohydrate broth - Answers No fermentation
Bright pink in phenol red carbohydrate broth - Answers Protein utilization
TSA - Answers General purpose
SBA - Answers Differential (hemolysis)
MSA - Answers Selective (salt) and differential (mannitol)
Bile esculin - Answers Selective and differential
BHI + 6.5% NaCl - Answers Selective for salt tolerance
Phenol red broth - Answers Differential only
Selective media - Answers Contain inhibitors
Differential media - Answers Show metabolic differences
Growth in MSA interpretation - Answers Salt tolerant
No growth in MSA interpretation - Answers Not salt tolerant
Yellow in MSA interpretation - Answers Mannitol fermented
Red in MSA interpretation - Answers Mannitol not fermented
Black > half in bile esculin - Answers Positive
Primary stain - Answers Crystal violet
Mordant - Answers Gram's iodine
Decolorizer - Answers 95% ethanol
Counterstain - Answers Safranin
Gram-positive color - Answers Purple
Gram-negative color - Answers Pink/red
Gram-positive cell wall - Answers Thick peptidoglycan
Gram-negative cell wall - Answers Thin peptidoglycan + outer membrane
Function of mordant - Answers Forms CV-I complex
Function of decolorizer - Answers Removes stain from Gram-negative
Heat fixing purpose - Answers Kills cells and adheres cells to slide
Total magnification - Answers Ocular × objective
100× objective requires - Answers Immersion oil
Oil function - Answers Reduces refraction and increases resolution
Resolution - Answers Ability to distinguish two close objects
Parfocal - Answers Image stays in focus when switching objectives
Coarse focus use - Answers 4× and 10× only
Fine focus use - Answers 40× and 100×
Bacteria appear transparent because - Answers ~80% water
Phase contrast microscope - Answers Used to view internal structures without stain
Reagent for catalase test - Answers Hydrogen peroxide
Positive result for catalase test - Answers Bubbles
Negative result for catalase test - Answers No bubbles
Function of catalase - Answers Breaks down hydrogen peroxide
Detects in oxidase test - Answers Cytochrome c oxidase
Positive result for oxidase test - Answers Blue/purple within 30 seconds
Negative result for oxidase test - Answers No color change
Positive result for KOH test - Answers Strings form → Gram-negative
Negative result for KOH test - Answers No strings → Gram-positive
Purpose of KOH test - Answers Verify Gram stain
Red after reagents A & B in nitrate reduction - Answers Nitrate → nitrite (positive)
No color after A & B in nitrate reduction - Answers Add zinc
Clear zone in starch hydrolysis - Answers Positive (starch hydrolyzed)
Dark plate in starch hydrolysis - Answers Negative
Reagent for coagulase test - Answers Plasma
Clot formation in coagulase test - Answers Positive
No clot in coagulase test - Answers Negative
Used to identify in coagulase test - Answers Staphylococcus aureus
Yellow in phenol red carbohydrate broth - Answers Acid (fermentation)
Bubble in phenol red carbohydrate broth - Answers Gas production
Red in phenol red carbohydrate broth - Answers No fermentation
Bright pink in phenol red carbohydrate broth - Answers Protein utilization
TSA - Answers General purpose
SBA - Answers Differential (hemolysis)
MSA - Answers Selective (salt) and differential (mannitol)
Bile esculin - Answers Selective and differential
BHI + 6.5% NaCl - Answers Selective for salt tolerance
Phenol red broth - Answers Differential only
Selective media - Answers Contain inhibitors
Differential media - Answers Show metabolic differences
Growth in MSA interpretation - Answers Salt tolerant
No growth in MSA interpretation - Answers Not salt tolerant
Yellow in MSA interpretation - Answers Mannitol fermented
Red in MSA interpretation - Answers Mannitol not fermented
Black > half in bile esculin - Answers Positive
