LEQ: What is the role of ATP in
cellular activities?
Cellular Energy
Pages 72 to 75
Energy

What is energy?
◦ The capacity to do work

What is Kinetic energy?
◦ Energy of motion
◦ Heat (thermal energy) is kinetic energy given off
due the the movement of molecules

What is Potential energy?
◦ Stored energy that an object possess as a result
of its location or structure
◦ Chemical energy is potential energy available for
release in a chemical reaction
A diver has more potential
energy on the platform
than in the water.
Diving converts
potential energy to
kinetic energy.
Climbing up converts the kinetic A diver has less potential
energy of muscle movement
energy in the water
than on the platform.
to potential energy.
Thermodynamics

What is thermodynamics?
◦ The study of energy transformation
◦ Organisms are open systems
◦ In an open system, energy and matter can be
transferred between the system and its
environment
The First Law of Thermodynamics

According to the first law of
thermodynamics, the energy of the
universe is constant:
– Energy can be transferred and transformed, but
it cannot be created or destroyed

The first law is also called the principle of
conservation of energy
The Second Law of Thermodynamics
During every energy transfer or
transformation, some energy is unusable,
and is often lost as heat
 According to the second law of
thermodynamics:

– Every energy transfer or transformation
increases the entropy (disorder) of the
universe
Heat
Chemical
energy
(a) First law of thermodynamics
CO2
+
H2O
(b) Second law of thermodynamics
Biological Order and Disorder

Living things are ordered, decreasing
entropy - this requires an input of energy,
increasing entropy….
◦ Building macromolecules (dehydration
synthesis) decreases entropy by organizing
atoms into molecules, molecules into cells,
etc…
◦ In order to build / maintain organization
requires an input of energy which increases
entropy
Chemical Reactions

Endergonic Reactions
◦
◦
◦
◦
“Energy In”
Require a net input of energy
Rich in potential energy
Photosynthesis – takes in energy to produce
sugar; energy stored in bonds
Fig. 8-6b
Free energy
Products
Amount of
energy
required
(∆G > 0)
Energy
Reactants
Progress of the reaction
(b) Endergonic reaction: energy required
Chemical Reactions

Exergonic Reactions
◦ “Energy Out”
◦ Chemical reactions that release energy
◦ Cellular respiration – breaking bonds of sugar
to release energy
Fig. 8-6a
Free energy
Reactants
Amount of
energy
released
(∆G < 0)
Energy
Products
Progress of the reaction
(a) Exergonic reaction: energy released
Chemical Reactions

Cellular Metabolism
◦ Sum of all exergonic and endergonic reactions
in a cell
◦ Anabolic Pathways – consume energy to build
complex molecules from simple ones
(endergonic)
◦ Catabolic Pathways – release energy by
breaking down complex molecules into simple
ones (exergonic)
Chemical Reactions

Energy Coupling
◦ The use of energy released from exergonic
reactions to drive essential endergonic
reactions
Adenosine Triphosphate
Energy currency of the cell
 Powers nearly all cellular work through
energy coupling reactions

Adenine
Phosphate groups
Ribose
Fig. 8-9
P
P
P
Adenosine triphosphate (ATP)
H2O
Pi
+
Inorganic phosphate
P
P
+
Adenosine diphosphate (ADP)
Energy
ATP – ADP Cycle
ATP + H2O
Energy from
catabolism (exergonic,
energy-releasing
processes)
Phosphorylation - adding a phosphate
ADP + P i
Energy for cellular
work (endergonic,
energy-consuming
processes)
Cells use ATP

Three types of cellular work that are
powered by hydrolysis of ATP
◦ Cell Transport – Bringing materials into cells
◦ Mechanical Work – muscle contractions
◦ Chemical Work – macromolecule synthesis
Fig. 8-11
Membrane protein
P
Solute
Pi
Solute transported
(a) Transport work: ATP phosphorylates
transport proteins
ADP
+
ATP
P
Vesicle
Cytoskeletal track
ATP
Motor protein
Protein moved
(b) Mechanical work: ATP binds noncovalently
to motor proteins, then is hydrolyzed
i