Which step in the gram stain is the critical step in differentiating gram-positive cells from gram-negative cells? a) safranin b) alcohol-acetone c) iodine d) crystal violet

The correct answer is: B) alcohol-acetone

Gram staining includes next steps:

•Fixation- usually  by heating or by using methanol

•Primary stain (crystal violet)- it stains all cells blue/purple  

•Mordant- added to form a crystal violet iodine

•Decolorization- distinguishes gram-positive from gram-negative cells. Acetone or ethanol are usually used. Acetone/ethanol extracts blue dye from Gram - bacteria (the lipid-rich, thin wall) more than from the, Gram + bacteria (lipid poor, thick walled).  The Gram -bacteria appear colorless and Gram + bacteria remain blue.

•Safranin-the red dye stains the decolorized Gram- bacteria.

1. a host loses nutrients to a parasite

2. a parasite only benefits when the host is alive (cause if the host dies the parasite dies with it )

3. producers to consumers

4. the tapeworm is a parasite

5. they convert energy from the sun (photosynthesis)

6. sunflower-robin (i think im 80% sure)

7. producer

8. consumer

9. prey

10. fresh water snails ( cause the green algea is the producer and the snails are the primary consumers and the small fish consumer so is the big fish)

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