ATP- Energy Stored in Chemical Bonds
Doug Foster/ CSUN
Principle(s) Illustrated
Energy stored in chemical bonds.
StandardsCA State Science Standard (1998/2007)
1. All living organisms are composed of cells, from just one to many trillions, whose details usually are visible only
through a microscope. As a basis for understanding this concept:
d. Students know that mitochondria
liberate energy for the work that cells Fig. 1 Top: Using poppers and ping pong balls to
do and that chloroplasts capture sun- model ADP, Pi, and ATP.
light energy for photosynthesis. Bottom: molecular models of the same.
Possible Script:
Teacher: Today I'm going to present a model for the action of ATP. What is a model?
Student(s): A representation of an object, system, or concept.
Teacher: This representation has some shortcomings, but the the basic concepts are
accurate...
Teacher: I am going to drop this popper/ping pong ball combination. BUT before I do...
Teacher: How high do you think it will bounce?
Student(s): Students give various estimates.
Teacher: What causes it to bounce at all?
Student(s): Students give various answers.
Teacher: What causes it to fall? What if I were to release it in the International Space Station?
Student(s): Gravity.
Teacher: What is gravity?
Student(s): Students give various responses. (Wait for "force.")
Teacher: What is a force?
Student(s): Something that causes movement
Teacher: Good. So a force is something that causes movement.
Teacher: Now we have to be precise. If we look more closely,what is happening when I release
a ball and allow gravity to affect the mass?
Student(s): The force causes the mass to accelerate.
(camera snaps an image every
3/100 sec- distance popper the
falls between frames
is increasing; it's accelerating)
Teacher: If the mass falls on something,
say a teeter totter with a mass
at the opposite end, what
happens to the mass at the opposite
end?
Student(s): Mass ascends
Teacher: What caused to ascend? Fig. 2 Popper accelerating
Student(s): ?
Teacher: Was something transferred from the falling mass to the mass at rest that caused it to
ascend?
Student(s): yes?
Teacher: What was that something?
Student(s): energy
Teacher: What' energy
Student(s): ? The ability to do work
Teacher: What's work?
Student(s): distance x force
Teacher: Lets stop for a moment and talk about these terms... we use them casually in
everyday life, but in science they have very precise meanings. So... (write)
mass- a property of matter measured by its resistance to a change in speed or
direction. (Adpated from Free Dictionary) (unit: kilogram (gram))
force- that property, which exerted on a mass, causes acceleration. (unit: newton)
work- force exerted over a distance (unit: joule)
energy- the capacity (≈ ability) to do work (unit: joule)
Teacher: All four of these terms are properties. Which 2 are measured with the same units?
work and energy
Teacher: Work and energy are very closely related.
(NOTE: A third property, HEAT, is also measured in joules... we'll return to this in a
latter lesson. )
Teacher: The properties of work and energy are so closely related that the same units are
used for their measurement...
Teacher: It leads to the idea that energy can be viewed 2 ways;
potential (≈ stored) energy
kinetic (≈ motion) energy
Teacher: So when the normal popper/ping pong ball combo is raised to a certain height, it has
potential energy. When it is dropped, it contains energy due to its motion (kinetic energy).
Teacher: So NOW I'll drop the popper/ping pongball...
(Drop and estimate the height)
Teacher: Teacher:Now I'm going to change the the poppers shape by inverting it with a ping
pong ball. What's taking place during the inversion?
Student(s): applying a force over a distance (albeit a short distanca), causing it to change
shape.
Teacher: What have I added to the popper?
Student(s): potential energy
Teacher: NOW I'll drop the popper/ping pong ball combination again.
(Teacher drops popper/ping pong ball (Ping pong ball will slam into ceiling... DON'T
SUB THE PING PONG BALL WITH ANYTHING HAVING A SIGNIFICANT MASS!)
Teacher: Why did the
popper/ping ball
bounce much higher
than they did before
inverting the
popper?
Student(s): The act of
inverting the ping
pong ball added
additional potential
energy.
Teacher:Can I get the same
effect by moving to
another part of the Fig. 3 Popper dropper
room?
(Move to another part of the room and repeat the drop).
Student(s): Yes.
Teacher: Absolutely... Here's the take home... It is also possible to store energy in the bonds
that hold atoms together. When an extra phosphorous is added to ADP, a molecule
with high potential energy is created. This molecule can be moved to other parts of
the cell to provide energy.
The energy required to attach a P to ADP can come from multiple sources. For
organisms near or at the Earth's surface, the most significant is light. Light provides
the energy to make ATP during the "light reactions" of photosynthesis.
How important is this molecule for providing energy throughout the cell?
The energy stored in ATP is used to force other chemical reactions to happen. These
chemical reactions can cause motion, release heat, and produce and/or destroy
other molecules.
Fig. 4. How important is ATP...?
Prior knowledge & experience:
Students know that something (energy) stored in batteries can cause cell phones to function, something in gasoline allows cars to move, something in food allows animals to move
Root question:
How do living things store energy?
Target response:
Energy is stored in the bonds between atoms. In living things, the bond between 2 phosphate atoms in ATP stores energy that can be usedin other parts of the cell. All chemical bonds store energy; ATP is significant because it can carry and release the energy held between the #2 and #3 phosphate atoms.
Common Misconceptions:
Idea that energy can be stored is not necessarily a misconception, but the details can be difficult to appreciate. There are some very precise terms.
The role of oxygen in the transfer of energy in aerobic organisms not always clear. Most students appreciate food is required for energy, but the role of oxygen in extracting energy from food is often not understood. Idea that respiration is combustion in slow motion sometimes helps make the connection more clear. Leads into the relationships between mitochondria, oxidative respiration, glucose, and ATP production in all eukaryotes.
Photographs and Movies
Fig. 5 Production of ATP by photosynthesis.
Fig. 6 Overview of ATP