Question

1. why must fresh cells be used when performing a gram stain? all of these are reasons why fresh cells must be used for gram staining. old cells may not gram - stain properly. as cells ages, they wont stick to the slide. fresh cells do not smell as badly as older cells. 2. after grams iodine is added, what color do the cells appear under a light microscope? all cells appear colorless all cells appear pink/red some cells may be purple and some may be pink/red all cells appear purple 3. when ethanol is applied correctly, gram - positive cells appear ____ and gram - negative cells appear ____. colorless; purple pink/red; purple purple; colorless purple; pink/red

Explanation:

1. Old cells may not retain the Gram - stain properly due to changes in their cell wall structure over time. This is the main reason fresh cells are used. The other options about smell and sticking to the slide are not the primary reasons.
2. After adding Gram's iodine, which acts as a mordant, all cells appear purple because it forms a complex with the crystal violet stain already present in the cells.
3. When ethanol is applied correctly, gram - positive cells retain the crystal violet - iodine complex and appear purple, while gram - negative cells lose the complex and are counter - stained pink/red by safranin.

Answer:

1. Old cells may not Gram - stain properly.
2. All cells appear purple.
3. purple; pink/red