Question

observing human cheek cells
procedure:

1. put a drop of methylene blue on a slide. caution: it will stain clothes and skin.
2. gently scrape the inside of your cheek with the flat side of a toothpick. scrape lightly.
3. stir the end of the toothpick in the stain and throw the toothpick away.
4. place a coverslip onto the slide.
5. use the scanning objective first and use the coarse adjustment knob to bring the slide into focus. cells will appear very tiny at this magnification.
6. switch to the low power and use the coarse adjustment knob. cells should be visible, but they will be small and look like nearly clear purplish blobs. if you are looking at something very dark purple, it is probably not a cell.
7. once you think you have located a cell, switch to high power and focus using the fine - adjustment knob. (remember, do not use the coarse adjustment knob at this point.)

observations → sketch the cell at low and high power.
label the nucleus, cytoplasm, and cell membrane. draw your cells to scale (as they appear in your view).
scanning
low
high

1. why is methylene blue necessary?

to see the white cells.

1. the light microscope used is not powerful enough to view other organelles in the cheek cell. what parts of the cell were visible?

cells

1. list 2 organelles that were not visible using a light microscope, but can be found in most animal cells?
2. the mouth is the first site of chemical digestion in a human. your saliva starts the process of breaking down the food you eat. what organelle do you think would be numerous inside the cells of your mouth? explain your choice.

Explanation:

1. Methylene blue is a stain. It is necessary to stain the cells to make them more visible under the light - microscope as cells are transparent and difficult to see without staining. The answer "To see the white cells" is incorrect as it is used to see all cheek cells, not just white cells.
2. With a light - microscope, the nucleus, cytoplasm, and cell membrane are visible in cheek cells. The answer "Cells" is too general.
3. Organelles like ribosomes and endoplasmic reticulum are too small to be seen with a light - microscope but are present in most animal cells.
4. Salivary glands in the mouth secrete saliva which contains enzymes for chemical digestion. Enzyme production and secretion require energy. Mitochondria are the power - houses of the cell, responsible for producing ATP (energy). So, mitochondria would be numerous in mouth cells to provide energy for the production and secretion of digestive enzymes.

Answer:

1. Methylene blue stains cells to make them more visible under the light - microscope as cells are transparent.
2. Nucleus, cytoplasm, and cell membrane.
3. Ribosomes, endoplasmic reticulum.
4. Mitochondria, because the mouth is the first site of chemical digestion and saliva production requires energy which mitochondria provide.