HOW MANY CELLS MAKE UP MY BODY?

HYPOTHESIS

Of course you know that there are a lot of cells in the human body. Guess how many they are.

INTRODUCTION

It is impossible to count the cells, but you can estimate their number. Follow the instructions.

MATERIALS

Cubes of 1 cm3, salt crystals, calculator

PROCEDURE

1. Pretend  that a bee is made of a single cell. Represent this cell with a cube of 1 cm3.

2. With the help of the cubes at your disposal, estimate the number of cubes needed to make an earthworm.

3. Repeat the esteem for any organisms in the following table n. 1 and complete the second column.

4. Fill in the third column of the table n.1 with the order of magnitude corresponding to the number of cm3 in each organism.

Table n. 1

• Since a bee  is actually made of more than one cell, you have to repeat the calculation  starting with a multi-celled bee. Compare the size of a salt crystal with the size of a cube. Let's say that you need 100000 (105) salt crystals to fill  1 cm3.
  Calculate how many salt crystals correspond to each organism in the following table n. 2 and complete it (indicate the order of magnitude).

Table n.2

• The average size for an animal cell is 10 microns or 10 millionths of a meter (10-5 m). That means that there are approximately 10-4 cells in one salt crystal. Eventually you now are able to estimate how many cells are in each organism and to complete the following table n.3.

Table n.3

QUESTION

Write down  at least one way in which our calculation is inaccurate.

Table n. 1

Table n.2

Table n.3

CONSIDERATIONS

It is impossible to estimate with accuracy the number of cells in a human body. Web sources report esteems between 1013 and 1014.  

There is really no way to know the exact number of cells in a human body, because the number varies from person to person, depending on their size.

Besides, the number of cells in an organism is constantly changing, as cells die or are destroyed and new ones are formed.