NOTES – Cell Energy Part 1
Adenosine Triphosphate (ATP)
Why do cells need energy?
In what ways are our cells like a tower?
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Are they organized? Do they have
structure?
There there forces in the environment that
act to destroy the cell’s structure
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Randomly moving molecules
Physical forces
Chemical attack
Disorder (entropy) is always on the
increase
How can cells maintain their highly
ordered structure?
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It takes energy, work, and information to
maintain order
Cells need energy just to stay the way
they are and not break down
What do cells use energy for?
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Repair themselves
Growth
Reproduction
Movement
Active transport
Protein synthesis
ATP – The “energy currency” of the cell
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ATP molecules are the basic energy source
for cells
ATP stands for adenosine triphosphate
ATP molecules carry just enough energy to
power a variety of cell activities
Structure of ATP
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ATP molecules have three parts:
1. Adenine (a nitrogen-containing compound)
2. Ribose (a 5-carbon sugar)
3. 3 Phosphate Groups
ATP Molecule
How does ATP store energy?
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Chemical energy is
stored in the bond
between an ATP
molecule’s second and
third phosphate group
Breaking the bond
releases energy for
cellular work
ATP becomes ADP
(adenosine diphosphate)
The ATP Cycle
1. Energy is used to
bond ADP to a free
phosphate creating a
high-energy ATP
molecule
2. ATP is broken down
into ADP, releasing
stored energy for
cell work
The ATP Cycle Continued
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ATP is a high-energy
molecule
ADP is a low-energy
molecule
When ATP is broken
down, ADP and the
extra phosphate can
be recycled into more
ATP
ATP Cycle Equations
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Cell storing energy (endergonic):
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ADP + P + energy  ATP
Cell releasing energy (exergonic):
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ATP  ADP + P + energy
ATP is like a rechargeable battery
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Batteries are used, giving up
their energy and can only be
reused after the input of
new energy
ATP is the recharged battery
while ADP is the used
battery
When the third phosphate is
cut loose, ATP becomes ADP,
and the stored energy is
released.
The input of additional
energy (plus a phosphate
group) "recharges" ADP into
ATP
How fast is the ATP cycle?
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A working muscle cell recycles all of its ATP
about once each minute
That’s about 10 million molecules of ATP
consumed & regenerated per second, per cell!
(600 million molecules per minute!)
If ATP was not continuously regenerated, you
would need to consume an amount roughly
equal to your bodyweight every day to meet the
energy needs of your cells!
How do cells make ATP?
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There are a variety of processes that different
types of cells use to produce ATP
Eukaryotic cells produce ATP during 2 main
processes:
1. Photosynthesis (plant cells only) – ATP is
made using energy from the sun, then
immediately used to help chloroplasts make
larger food molecules
2. Respiration (plant and animal cells) – ATP
is made using energy from food molecules
Cells use ATP molecules for their
energy needs
As ATP is used up, more is made
by the cell
Cells need a continuous input of
energy in order to keep making
ATP