cells can be seen with a light microscope. The chart shows a huge
range of sizes, from fractions of a nanometer of atoms to the meter
sizes of humans.
First, let us step back and get the big picture on the size of cells. We know cells are small, but how small? The chart
below shows the relative sizes (on a logarithmic scale) of a typical
cell, compared with the sizes of other things in nature.
Structure and Function
Now let's learn
the different parts and functions of cells. Here we want to think
about how the organization inside each cell keeps them alive and
below gives some examples of how living things assign and divide
up jobs that are needed for breathing to occur.
- control of breathing
exchange in lungs
Cells are organized
by the jobs they perform in living things. The main jobs of cells
are as follows:
|Hold cell materials together
||Regulate which molecules can go in and out of
cells. Detect chemical signals outside of cells and translate
"message" to inside.
|Capture and use energy
||Plant cells - trap energy of sunlight. Animal
cells - convert energy of food.
||Repair, provide building materials for growth
and for new cells.
|Make new cells
||Control division to make new cells. Sex cells:
reduce the genetic material by half.
Performs the Work of Cells
|Cells contain certain smaller
structures, known as organelles. They perform the work of cells.
Organelles are thus one level of organization for life functions.
Details on what these organelles do are
given in the other units of "Cells Are Us."
For a 3-dimensional drawing of a
cell and its organelles,
For animated illustrations of each
organelle and its functions,
click here. (At this site, click on the
name of each organelle to see animation and explanation).