How do I get a gumball
if I only have $1?
Change the form of the
money!
Food molecules are the
$1000 dollar bills of energy
storage!
They function as fuel molecules,
storing large quantities of energy
in a stable form over long periods
of time.
BUT our cells can’t directly use
that energy, so it needs to be
converted into ‘coins’
• $1000 bill
Coins
Glucose is then stored in the bonds
of the ATP molecule so the cell can
use the chemical energy!
Glucose
The Main Energy Source for Cells
Glucose contains WAY
too much energy for
the cell to use at one
time!
So…
what has to happen?
ATP
One Powerful
Molecule
ATP provides chemical
energy for cellular work!
ATP = adenosine triphosphate
1. adenosine molecule
2. ribose (5-carbon sugar)
3. triphosphate tail
ATP --> ADP + P + Energy
ADP + P + Energy ---> ATP
The ATP-ADP
Cycle. Energy
is needed for
the formation
of ATP and is
released as
the ATP is
converted
back to ADP
and
phosphate.
ATP/ADP Cycle
• Where is a phosphate added?
• Where is a phosphate removed?
ATP/ADP Cycle
1. Glucose enters a cell.
2. It is broken down releasing energy
from its bonds
3. This energy is stored in a bond
between a molecule of ADP and a
phosphate (P) molecule resulting in
an ATP molecule.
4. When this energy is needed, the
last phosphate molecule (P) is
broken off, releasing the stored
energy from the bond. ADP results.
• ATP  ADP + energy
(energy is released & used)
• ADP + energy  ATP
(energy is stored)
• SUMMARY: Our food is broken
down into glucose. Our cells
cannot use glucose as a source
of ENERGY so the energy from
glucose must be used to make
ATP for cells. ATP is made of an
adenosine molecule with 3
phosphates attached. ENERGY
is stored in the bonds of
phosphates.
• When a phosphate is broken
off the ATP molecule, ENERGY
is *released* & the molecule is
called ADP now. When energy is
available again (from the food
we eat) it will reattach a
phosphate to ADP to make ATP
again. The body will then be
storing energy for when it is
needed.