UNIT 1 Living organisms Natural Science 2. Secondary Education THE SIZE OF CELLS
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UNIT
1Living organisms
Natural Science 2. Secondary Education
THE SIZE OF CELLS
UNIT
1The size of cells
Natural Science 2. Secondary Education
How can we measure a cell?• Cells cannot be seen by the naked eye, so it is difficult to get an idea of their size or measure them. Because they are so small, cells must be measured in tiny units called micrometres (µm).
1cm 2 3 4 5 6 7 8 9 10
1mm 2 3 4 5 6 7 8 9 10
To get an idea of how big a micrometre is, think of one of the centimetres marked on a ruler: each centimetre contains 10 mm.
Now think of one of those millimetres. A single millimetre contains 1000 µ.
1000 µm
Comparing sizes• Imagine we measure an eukaryotic cell and see that it has a diameter of about 15.5 µm. This is an average-sized cell.
1cm 2 3 4 5 6 7 8 9 10
= 640 cells
15,55 µm
•How many of these cells would fit in a single millimetre?
• 1,000 divided by 15.5 equals to 64.5, so we could line up 64 of these cells in a row of one millimetre
• Therefore, 640 cells would fit in 1 centimetre.
UNIT
1The size of cells
Natural Science 2. Secondary Education
Magnifying images in order to see cells• Microscope lenses magnify what we see through them many times. Normally a microscope has several lenses of increasing magnification so that we can see cells or tissue specimens in great detail.
10x magnification
40x magnification
UNIT
1The size of cells
Natural Science 2. Secondary Education
100x magnification
Two different-sized cells
• Microscope lenses magnify what we see through them many times. Normally a microscope has several lenses of increasing magnification so that we can see cells or tissue specimens in great detail.
UNIT
1The size of cells
Natural Science 2. Secondary Education
Magnifying images in order to see cells
10x magnification
40x magnification
UNIT
1The size of cells
Natural Science 2. Secondary Education
Problem solving and investigating, page 18, question 7
•We observe the bacteria in the photo (10,000x magnifications) and we will find out the real length of one of them.
•To calculate the real size of the cell we have to divide the size of the cell in the photo ( in mm) by the number of magnifications.
•3 centimetres or 30 mm long divided by 10,000 magnifications equals to 0.003 mm or 3 micrometres is the real size of the cell.
•How many of these bacteria would fit in a millimetre?
•1000 divided by 3 equals to 333 would fit into 1 millimetre
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