This document discusses metabolic heat production in cells and the thermodynamics of biological processes. It explains that cells are open systems that exchange matter and energy with their surroundings. The spontaneity of biological reactions depends on the change in free energy, enthalpy, and entropy. Exothermic reactions driven by a decrease in enthalpy can proceed spontaneously even if the change in entropy is negative. Temperature also influences spontaneity, as reactions with negative entropy changes can be spontaneous at low temperatures but not at higher temperatures.

1. Metabolic Heat Production
Cellular Engineering
UPIIG-IPN
Author: Guillermo Garibay Benítez University: Instituto Politécnico Nacional
Mexico

2. Changes in free energy and enthalpy
• A system is said to be open and closed
according wether it can exchange matter and
energy with its surroundings.
• Because cells take up nutrientes, release
metabolites, and generate work and heat,
they are open systems

3. • The state of a system is defined by a set of
state functions which besides the free energy
G include enthalpy H, equal to the heat
absorbed at constant pressure and entropy S,
a measure of degree of order in the system

4. • Spontaneous processes generally occur in a
direction that increases the overall disorder
(entropy) of the system.
• The total entropy contained in the products is
greater than the entropy contained in the
reactants.
• Thus, one might say The process is “entropy
driven”.

5. • The spontaneity of a process is not be decided
by the entropy change, and some reactions
with ΔSR < 0 proceed very well.
• These exothermic reactions are accompanied
by a large release of heat Q to the
surroundings.
• These reactions have a large, negative increase
in the enthalpy H of the system:
• One might say the reaction is “enthaply driven”

6. • Most endothermic reactions (ΔHR > 0) will not
proceed spontaneously, even when ΔSR > 0,
since the change in enthalpy has a much
greater influence on ΔGR than has ΔSR.
• The process has a positive affinity, it proceeds
spontaneously when AGR<0
• ΔSR contribution to ΔGR is proportional to the
absolute temperature T.

7. • Since ΔHR and ΔSR are weak functions of T, a
process with negative ΔSR can have a positive
affinity at low temperature, but a negative
affinity at higher T.
• An example is the folding of proteins to their native,
active form. Both AHR and AHR are negative (the
process is exothermic, but the folding increases the
“order” of the system).
• At low temperature the folded protein is stable,
while the unfolded, denatured protein is stable at
higher temperatures.

8. • How does an DSC works? And what kind of information do we obtain? Explain
main principles.
• How does a thermodynamic analysis of proteins explains protein
denaturation?
•How do we obtain heat capacity of a protein? What other parameters do we
need to obtain heat capacity?
• Why does a DSC study is better for denaturation studies rather than
spectroscopic studies?

9. • For the reaction:
ΔG° = Free energy of reaction at standard conditions.
• At equilibrium:

10. • Reordering:
• Equilibrium constant:
•

12. Determine ΔGR

14. Temperature influence on specific growth rate
• The influence of temperature on the maximum specific growth
rate or a microorganism is an increase with increasing
temperature up to a certain point where protein denaturation
starts, and a rapid decrease beyond this temperature.
• For temperatures below the onset of the protein denaturation,
the maximum specific growth rate increases in much the same
way as for normal chemical rate constant:
• A is a constant and Eg is activation energy of the growth
process

15. • Assuming that the proteins are temperature-
denatured by a reversible chemical reaction
with free energy change ΔGd and that
denatured proteins are inactive an expression
for µmax is proposed: