Page 13 - 新思维科学学生用书7 样章

1 Cells

Parts of an animal cell

All animals are made of cells. You
are an animal, and your body cell membrane
is made of cells. No one knows cytoplasm

exactly how many cells there
are in a person. One estimate mitochondrion
is about 100 trillion. That is

100 000 000 000 000 cells. nucleus
Animal cells are similar to plant
cells in several ways. They have
a cell membrane, cytoplasm, An animal cell
mitochondria and a nucleus.

Think like a scientist

Looking at animal cells through a microscope

This task gives you more practice in using scientific equipment safely.

You will need:
• a microscope, a microscope slide, a cover slip, a cotton bud, some methylene
blue, a dropper pipette, safety glasses

Safety
Put on your safety glasses.
1 Very gently rub the cotton bud along the inside
of your cheek. This will collect some loose cells.

2 Rub the cotton bud on the surface of a clean
microscope slide. You will not be able to see
the cells yet, because they are so small.

3 Use a dropper pipette to add a drop of
methylene blue to the cells. Methylene
blue is a dye that will stain the cells blue,
making them easier to see.
4 Carefully lower a cover slip over the drop of blue stain.

5 Put the smallest objective lens over the stage.
6 Put the slide onto the stage, with the part you want to look at over the hole in
the stage.

7 Looking from the side, turn the focussing knob until the lens is close to the slide.

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