BI110 Study Guide - Midterm Guide: Atp Hydrolysis, Oxidative Phosphorylation, Acetyl-Coa

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Biology Review Part 3
Module 22- Metabolism
Chemical Reactions
aB + bB <---> cC +dD
A and B are reactants; C and D are products, and a, b, c, and d represent the number of moles
The reaction is reversible, but the actual direction and rate at any one time depends on the energy and on the
concentrations of A, B, C, and D
-Basic chemical reactions, reactions are reversible but the actual direction and rate at any one time depends on the
energy and on the concentrations of A,B,C and D
Energy-It is the capacity to do work (kinetic, potential, light, heat, mechanical, chemical, electrical/ion gradients)
Energy can be converted readily from one form to another
Thermodynamics
Study of energy and its transformations
Different types of thermodynamics systems
o Open systems exchange energy and matter with their surroundings, and are most important in biology
o Closed system does not exchange matter with its surrounding- energy is constant and does not change
First law of thermodynamics
Energy can be transferred and transformed but not
created or destroyed
o Conservation of energy
Total amount of energy in a system and its
surroundings remains constant
Second law of thermodynamics
Each time energy is transferred or transformed,
some is lost (i.e. becomes unavailable to do work)
Energy transfers and transformations are never
100% efficient
Energy most often lost as heat; this heat increases
the kinetic energy of molecules by increasing their
random motion, which increases the disorder (or
entropy) of a system and/or its surroundings
o Entropy (total disorder of a system and its
surroundings) always increasing
o Entropy of universe is always increasing
(measure of disorder)
Thermodynamics
1st (Law of conservation of energy): Energy
cannot be created or destroyed, it can only be
transferred or transformed
2nd Law of Thermodynamics: The transfer or
transformation of energy increases the entropy of
a system and its surroundings (entropy is always
increasing)
o Conversion of energy is not 100% efficient;
some energy becomes unavailable to do
work (i.e. is lost to entropy)
Life and the second law of thermodynamics
Life is highly ordered (keeps entropy low), which
suggests that it goes against the second law of
thermodynamics
Living things bring in energy and matter to
generate order out of disorder
o Local increase in order (decrease in
entropy)
o Entropy of surroundings (and universe as a
whole) increases
ORDER IS EVERYTHING
Entropy always increasing but an organism has a very low entropy
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We eat to maintain low entropy (heat is released when creating order in an organism by using energy)- Not all
entropy of all systems is always increasing
o The entropy of water would increase as it changes from ice to a liquid, and then to a gas
Metabolism and Energy
All metabolic reactions (an entire metabolic pathways)
involve in the input or release of energy
The energetics of a reaction/pathway defines the type
of metabolism
Catabolic (break down) or anabolic (build up)
o Energy flows through cellular processes (total
energy= usable energy+ unusable energy---
H=G+TS), Total energy is called enthalpy (H),
usable energy is called free energy (G),
Unusable Energy is Entropy (S)
The amount of Free Energy (G) changes when a system
changes
The change in free energy (delta G) can be calculated
for any reaction
Delta can be calculated for every thing involved in the
equation except temperature
Total potential energy (Enthalpy H)= usable energy
(G)+ unusable energy (Entropy S)
o H= G + TS (T- Temperature)
Free Energy (Delta G)
As a reaction goes to completion, it is influenced by two factors:
o Changes in energy content: Delta H (final- initial)
o Changes in entropy: Delta S (Final- initial)
For spontaneous reactions the delta G will be negative (does not mean fast, it is energetically favourable)
For reactions that are not spontaneous they will be positive
Gibbs Free Energy (will not be the same for different reactions)
Exergonic reactions- Spontaneous, energetically
favourable (net change is negative because energy
of reactants is higher than products)
o Some reactions will release more or less energy
(larger delta G proceeds more quickly)
o System gives up potential energy (H)
o Catabolic processes- increasing disorder
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Endergonic reactions- Not spontaneous, energy
needs to come form somewhere for the reaction to
occur (net change is positive)
o Some reactions will use more or less energy
(larger delta G proceeds faster)
o The system gives up order (entropy increases)
o Anabolic reactions (increasing order by creating
new bonds)
Delta G at zero refers to equilibrium so no
reaction occurs
Spontaneous Reactions (-Delta G)
"Spontaneous" doesn't necessarily imply quick;
it means "energetically favourable"
o Delta G= deltaH - TdeltaS
Two factors can give rise to -deltaG, and therefore spontaneous reactions:
o Negative deltaH (System gives up potential energy(H)
o Products are less ordered than reactants (Large positive deltaS- the system gives up order and entropy
increases)
Chemical Reactions, Free energy, stability and Equilibrium
Equilibrium does not mean equal concentration, it means that conversion of products to reactants and vice versa
will be equal
Biological organisms never reach equilibrium, they are open systems
o Constantly bringing in products, taking away products (concentrations are different)
o Metabolism never stops and constantly requires energy
Free Energy Summary
Free energy changes when the potential energy and entropy of substances changes
Chemical reactions run in the direction that lowers the free energy of the system
Exergonic reactions are spontaneous (release energy) while endergonic reactions are non-spontaneous (require
input of energy)
Equilibrium in Living Systems
Living systems are open
Organisms never reach equilibrium (DeltaG=0)
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