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Energy 1: Cellular Energetic Theory

1 of 5 of my Energy Domain. Image Credits: Biology (Campbell) 9th edition, copyright Pearson 2011, & The Internet Provided under the terms of a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. By David Knuffke.
by

Eric Tucker

on 29 October 2014

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Transcript of Energy 1: Cellular Energetic Theory

Cellular Energetics
Theory
2 Relevant Laws:
First:
Second:
Matter, and energy can not* be created or destroyed.
Transformations ARE ALLOWED!
Any closed system will tend toward a state of maximum
entropy
.
True for the Universe as a whole.
Portions of the Universe can still function as "open" systems.
Energy (and the matter that accompanies it) can be used to decrease an open system's entropy.
Cellular Energy Theory:
Gibbs Free Energy:
Kinetic & Potential Energy
Organisms are energy processing systems.
Energy from the Sun, or from Chemical Bonds is used to undertake cellular/organismal work

Work
: Anything that requires atoms to be moved around through cellular actions (aka: "everything you do")
Both are useful to organisms for different purposes.
Both contribute to phenomena at all levels of organization in the Universe.
A Measurement of the amount of "useful" energy that a system (like a cell) can use for performing work.

At the cellular level, the major biological source of energy is from the rearranging of atoms to from higher energy compounds to lower energy compounds.
Exergonic Reactions:
Endergonic Reactions:
Release energy (matter is converted from higher energy arrangements to lower energy arrangements) .
Will happen spontaneously, once they are initiated.
Change in free energy is NEGATIVE.
Require energy input to occur (matter is converted from lower energy arrangements to higher energy arrangements) .
Can not occur spontaneously.
Change in free energy is POSITIVE.
G
=
H
-
T S
G = Free Energy
H = Enthalpy (energy stored in a substance)
T = Temperature
S = Entropy
Biological Systems use Exergonic Reactions to provide the free energy necessary for endergonic reactions.
Living systems are not the only systems in the universe that require energy conversion to function.
Life is Highly Ordered
Life Requires Energy Input
Organisms use the energy they convert to power cellular/organismal processes that decrease their overall entropy (or at least delay its increase). This process increases the entropy of their surroundings.
A highly ordered living system uses energy input to maintain/increase order
Open & Closed Systems
Closed systems inexorably tend toward an absence of free energy.

They reach at a state of equilibrium between inputs and outputs.
Closed
Inevitably Dull
Open
Open systems will not reach equilibrium as long as the processes of the system recieve inputs and produce outputs.

There is no inherent limit to the complexity of an open system, provided there is enough input to allow for that complexity
Usually Interesting
ATP!
The Return of Kinetics
Adenosine Tri-Phosphate
The short term energy storage/release molecule of choice in cells.
Tens of millions made and used per second per cell
The bonds between phosphate groups in nucleoside tri-phosphates (like ATP) are relatively unstable.
Much more free energy is released when the bonds between them are broken than is required by the cell to initiate their cleavage.
Energy!
ATP
ADP
Much of the work done by cellular proteins is mediated by the addition and removal of phosphate groups from ATP by proteins to other proteins (kinases and phosphatases).
Metabolism
Refers to the sum total of all chemical reactions that take place in an organism.

Energy from
catabolic
reactions (ex: respiration) is used to power the synthesis of ATP from ADP and Phosphate groups.

ATP (and other NTP's) is used to power the
anabolic
Reactions that require chemical energy.
Reaction Coupling
Refers to linking an exergonic process with a cellular process.


If an endergonic process requires less free energy than an exergonic process produces, coupling those two reactions allows for maximum efficiency, and an overall negative delta G.
The Reaction Profile
All reactions require an input of energy (the "
activation energy
") to make the breaking of current chemical bonds energetically favorable (the "
transition state
").

The relationship between the energy of the products and the energy of the reactants is what determines if a reaction is exergonic or endergonic.
Catalysts!
effect of catalyst
Any substance that increases the rate of a chemical reaction while not participating in the reaction.

Lowers the activation energy of a reaction.

Reusable (since they don't participate).
Big Questions:
Make Sure You Can:
How do living systems adhere to the constraints of the Universe?

How can a living system maintain order in a Universe of increasing entropy?
Explain how living systems adhere to the first and second laws of thermodynamics.

Explain how living systems can increase in order even though the Universe is moving toward a state of maximum entropy.

Compare endergonic and exergonic reactions.

Compare open and closed systems.

Explain how ATP allows for cellular work.

Explain the effect of a catalyst on a reaction profile.
* there are a few exceptions (e.g. stellar fusion), which don't matter for us
More PE, Less KE
Less PE, More KE
Life is an open system!
Equilibrium = Death
Full transcript