An introduction to
Cellular Processes
Learning Objectives
 SWBAT: Explain why all biological
systems require constant energy input to
maintain organization, grow, and
reproduce.
 SWBAT: Predict how changes in free
energy availability affect organisms,
populations, and ecosystems.
Living systems require free
energy and matter to . . .
 Maintain order
 Grow
 Reproduce
Organisms use various
strategies to . . .
 Capture
 Use
 Store
. . . FREE ENERGY.
What is free energy?
 Free energy = available energy
Let’s talk about energy
What is it?
What is it?
Energy – the capacity to do work;
the capacity to cause change
Forms of energy
 Kinetic energy= the energy of motion
 Thermal energy = the kinetic energy of randomly moving
atoms or molecules
 Potential energy= the capacity to cause change as a
result of an object’s location or arrangement
 Chemical energy = a form of potential energy available
for release in chemical reactions; stored in chemical
bonds
Thermodynamics
The study of energy transformations in a
collection of matter
Laws of Thermodynamics
1st Law:
 Energy can be neither created nor
destroyed. It can, however, be
transformed or transferred.
2nd Law:
 Every energy transfer or
transformation results in increasing
disorder within the universe.
 Entropy = a measure of the disorder
or randomness.
In almost every chemical reaction
some energy is converted to thermal
energy and released as heat.
Heat is a very disordered form of
energy.
Given that:
1. Life requires a highly ordered system
2. Cellular processes often consist of a series of
chemical reactions that release heat, and
therefore energy, at each step.
Does life violate the second law of
thermodynamics?
In living organisms, increased disorder
and entropy are offset by biological
processes that maintain or increase
order.
 One way to do this is to couple cellular
reactions that increase entropy
(=decrease free energy,= exergonic) with
those that decrease entropy (=increase
free energy, = endergonic)
 Put another way. . . Combine
energetically favorable, spontaneous
reactions (those in which the products
have less available energy than the
reactants) with those that have an
increase in the free energy in their
products vs. their reactants
 One such reaction that is energetically
favorable, spontaneous is the reaction
that converts
ATP  ADP
Energy input must exceed (or at least
match) energy lost to entropy.
Where does that energy come from in
living organisms?
 If acquired free (available) energy > required free
energy (expendable) 
energy storage or growth.
 If acquired free (available) energy < required free
energy (expendable) 
loss of mass and ultimately death of the individual,
population, and/or ecosystem.
 The energy related, coupled pathways in
biological systems are sequential and may be
entered at multiple points in the pathway.
 Examples:
 Krebs Cycle
 Glycolysis
 Calvin Cycle
 Fermentation
Learning Objectives
 SWBAT: Explain why all biological
systems require constant energy input to
maintain organization, grow, and
reproduce.
 SWBAT: Predict how changes in free
energy availability affect organisms,
populations, and ecosystems.