BIOL 1201 : Exam 3
Chapter 8: An Introduction to Metabolism10/9/2013 9:31:00 PM
Metabolism: the sum total of an organism’s chemical reactions
• 2 types
o Catabolic: pathways involved in degradation. Release energy
by breaking down complex molecules to simpler compounds
▪ Catastrophe: destroys/breaks down
▪ Energy is released
o Anabolic: pathways involved in synthesis. Consume energy to
build complicated molecules from simpler ones. Sometimes
called biosynthetic pathways
▪ Building (Anabolic steroids: building muscle)
▪ Requires energy
Organisms transform and transfer energy
• Energy: the capacity to do work
o Potential energy is the energy that an object possesses
because of its structure or position. Usually chemical bond
energy in biological systems
▪ Position: water bottle example: holding it in the air
(more potential energy) vs. setting it on the ground
(less potential energy)
o Kinetic energy is the relative motion of objects
• Energy transfers by organisms are subject to 2 laws of
thermodynamics
o First Law of Thermodynamics: energy can be transformed and
transferred. But it cannot be destroyed (i.e. the energy of the
universe is constant) [energy cannot be created or destroyed]
▪ Known as the principle of conservation of energy
o Second Law of Thermodynamics: states that every energy
transfer or transformation makes the universe more
disordered (i.e. every process increases entropy). In other
words, with every transfer of energy, some usable energy is
lost as “heat”
o Entropy (S) is the quantitative measure of disorder or
randomness
Free Energy and Spontaneous reactions
• Free energy (g) is the portion of energy available to do work
o ΔG = ΔH – TΔS
o It’s the difference between the total energy (ΔH, or enthalpy)
and the energy not available to do work (TΔS), where T is
the absolute temperature and S is entropy.
o In a chemical reaction, the energy change (ΔG) between
the reactants and the products is the amount of
useable energy that can be harvested to do work
▪ ΔG = ΔH – TΔS
▪ ΔG = G final products – G starting material
(reactants)
▪ IF delta g is a negative number, that means energy was
released
▪ If delta g is positive, that means that energy was used
(energy was required)
• As a chemical reaction approaches equilibrium the free energy
(delta G) of the system decreases
• When a reaction is pushed away from equilibrium, the free energy
(delta G) of the system increases
• At chemical equilibrium, delta G=0
• When delta G=0, no work can be done
o Farther away you get from equilibrium (0) the more work can
be done
• Delta G
o If delta G is negative, the forward reaction will occur
spontaneously, and energy will be released
o If delta G is positive, the forward reaction will not occur
spontaneously, energy will have to be added to the system in
order for the forward reaction to occur.
• Types of chemical reactions
o Based on their free-energy changes
▪ Exergonic – release energy when they occur
Negative delta G
Energy released
Products have less free energy than the reactants
Reaction is energetically downhill
Spontaneous reaction
Hydrolysis of ATP is an example
Document Summary
Chapter 8: an introduction to metabolism10/9/2013 9:31:00 pm. Metabolism: the sum total of an organism"s chemical reactions: 2 types, catabolic: pathways involved in degradation. Release energy by breaking down complex molecules to simpler compounds: catastrophe: destroys/breaks down, energy is released, anabolic: pathways involved in synthesis. Consume energy to build complicated molecules from simpler ones. Sometimes called biosynthetic pathways: building (anabolic steroids: building muscle, requires energy. Organisms transform and transfer energy: energy: the capacity to do work, potential energy is the energy that an object possesses because of its structure or position. In other words, with every transfer of energy, some usable energy is lost as heat : entropy (s) is the quantitative measure of disorder or randomness. Products have less free energy than the reactants. Hydrolysis of atp is an example: endergonic require input of energy to occur. Products have more free energy than reactants. Substrate a molecule that reacts with the help of an enzyme.
