Why is high surface area to volume ratio important
Surface Area to Volume Ratio Explained
[Music]
some organisms are big and some are
small but they're all made up of cells
some tiny organisms like bacteria are
made up of a single cell and all the
materials they need must be supplied via
their cell membrane large organisms like
us humans are made up of millions of
cells to get the important stuff like
oxygen to all of the cells that make up
our bodies we have a transport system
that take things to where we need them
we rely on the blood to transport what
we need to where we need it but why are
larger organisms made of many cells
rather than a single giant cell and why
do we need such advanced transport
systems rather than simply allowing
materials like oxygen to diffuse from
the air through our skin to all of our
body cells the problem is surface area
consider two cubes of different sizes
the smallest cube is 1 centimeter by 1
centimeter by 1 centimeter and so has
faces each with an area of one
centimeter squared and there are six
faces so it has a total surface area of
six centimeters squared the larger cube
is 2 centimeters by 2 centimeters by 2
centimeters so each face is 4
centimeters squared with 6 faces it has
a total surface area of 24 centimeters
squared so the larger cube has a larger
surface area but the larger cube also
has a larger volume we need to compare
the surface area of each cube with its
own volume the small cube has a volume
of one by one by one which is one
centimeter cubed
it has 6 square centimeters of surface
area for every one cubic centimeter of
volume we can say that it has a surface
area to volume ratio of 6 to one if we
do the same for the larger cube we can
see that it has a volume of 2 times 2
times 2 which equals 8 centimeters cubed
this ratio of 24 square centimeters of
surface area to every 8 cubic
centimeters of volume can be simplified
to 3 to 1
six to one is bigger than three to one
it's obvious that the smaller cube has a
larger surface area to volume ratio
let's imagine that these cubes are
living cells that need oxygen to survive
for oxygen to spread throughout the
cells it must diffuse through the
surface as the small cell has more
surface area relative to its volume
every part of that volume can be
supplied with oxygen at a faster rate
compared with the larger cell it would
take too long for the center of the
larger cell to be supplied with what it
needs
if a large organism were made of a
single cell the exchange of materials
simply wouldn't happen fast enough this
is what limits the maximum size of a
cell since our bodies have to be made of
many tiny cells it's important that the
materials those cells need are
transported directly to them this is the
reason why we have a circulatory system
with a really strong pump that is the
heart constantly shifting nutrients in
the blood throughout our body
[Music]
you
