Cheryl Is in a Lab Attempting to Prepare a Slide

question 29

Multiple Choice

Cheryl is in a lab attempting to prepare a slide of cow blood for observation in a wet mount.She places a small drop of the blood on a slide,adds a drop of strong saline (salt) solution,and then covers all of it with a coverslip.After returning to her desk,she observes the slide with her microscope and notices that all of the red blood cells (RBCs) do not look like the nice round donut-shaped cells in her lab manual.Instead,the RBCs look very shriveled up.Her lab partner,Derek,has also made a slide,but the RBCs on his slide do look like the ones in the lab manual.Derek used a more dilute solution of saline but the same vial of blood. The most plausible explanation for the appearance of the blood cells on Cheryl's slide is that the

• A) saline she used was hypotonic to the RBCs; this resulted in water osmosing through the RBC plasma membrane mostly into the cells.
• B) saline she used was isotonic to the RBCs; this resulted in water osmosing through the RBC plasma membrane into and out of the cells at an equal rate.
• C) saline she used was hypertonic to the RBCs; this resulted in water osmosing through the RBC plasma membrane mostly out of the cell.
• D) RBCs were hypertonic to the saline; this resulted in water osmosing through the RBC plasma membrane mostly into the cells.

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Definitions:

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