Biology 1002B Lecture Notes - Lecture 5: Enthalpy, Glutamine, Thermodynamics

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18 Apr 2012
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Lecture 5: Energy & Thermodynamics
(4.1-4.3)
Energy
Defined as the capacity to do work
All energy can be grouped into one of two different states: Kinetic and Potential
Kinetic
o Energy possessed by an
object because it is in
motion
o Waves in the ocean, a
falling rock, kinetic energy
of electricity (flow of
electrons), motion of
planets
Potential/Chemical Potential
o Stored energy: the energy
an object has because of its location or chemical structure
o A boulder at the top of a cliff has potential energy because of its position
in the gravitational field of Earth. The arrangement of atoms in a molecule
of glucose has potential energy stored in the specific arrangement of
atoms.
o Chemical potential: Energy associated with chemical bonds
Thermodynamics
Study of energy and its transformations
System
o Object being studied
o Three Types
Isolated System
Does not exchanged matter or energy with surroundings
Ex. Insulated thermos bottle
Closed System
Can exchange energy but not matter with surroundings
Ex. Earth
Open System
Both matter and energy can move freely between system
and surroundings
Ex. Anything living
Surroundings
o Everything outside the system
First Law of Thermodynamics
Energy can be transformed from one form into another or transferred from one
place to another, but it cannot be created or destroyed (Total energy is constant)
Also called principle of the conservation of energy
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Ex. Niagara Falls (as water moves, its potential
energy is converted to kinetic energy. The higher
the waterfall, the more kinetic energy the water
possesses. When it reaches the bottom of the
waterfall, the kinetic energy is dissipated into
various forms of potential and kinetic energy.
Similarly, the water flows into dam, and the
energy associated with the gravitational drop
spins the turbine which converts that energy into
electricity
Second Law of Thermodynamics
Energy transformations are not 100% efficient
o Each time energy is transformed from one
form into another, energy is lost and unable to
do work
o Lost in the form of heat (random molecular
motion)
Every energy transformation increases the
disorder/randomness (Entropy) of the universe
Disorder (entropy) of an isolated (isolated and close
mean pretty much the same thing in biology) system always increases
Physical objects always break down (This is why machines are never 100%
efficient, coffee gets cold, car engine gets hot, new car gets old and requires
repairs, etc)
The physical disintegration of an organized system is the second law in action.
Systems will move spontaneously to a more disordered, higher entropy state.
You can reverse, but this requires work. It takes energy to maintain low entropy.
Through the process of cellular respiration cells are able to convert only about
40% of the potential energy in glucose into a form usable for metabolism
Proteins always break down
The total disorder (entropy) of a system and its surroundings always increases
Life & Second Law of Thermodynamics
Quality of all life: highly ordered
o Ex. DNA helix, protein, ribosome
Proteins constantly breaking down (refer back to kleptoplasty and lecture 1).
Looking at chloroplast and mitochondria, it requires a lot of proteins to maintain
these organelles. The proteins needed to maintain these organelles are encoded
in the nucleus. If you isolate these organelle, they no longer have the protein
supply and break down much faster
Living cells = open systems
o Exchanging energy and matter with surroundings and
use that to generate order
Eat food to maintain low entropy (basically to maintain the
cells)
Second law states the entropy of a system and the
surroundings is supposed to increase?? Does life contradict
that? No.
o Living things give off heat and carbon dioxide which
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