Question

required information
gram positive cell

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.

1. 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

1. 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 can have changes in cell - wall properties that affect Gram - staining results, making fresh cells necessary.
2. Gram's iodine forms a complex with crystal violet, and all cells appear purple at this stage.
3. Gram - positive cells retain the crystal violet - iodine complex and remain purple, while gram - negative cells lose the complex and take up the counter - stain (safranin) to appear pink/red.

Answer:

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