Chapter 5: Bioenergetics I. The Importance of Energy A. Definition of ...

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BIO 330 Cell Biology



Lecture
Outline

Spring 2011

Chapter
5
:

Bioenergetics

I.
The Importance of Energy


A.
Definition of energy



Capacity to cause specific physical or chemical changes


B.
Types of work in the cell



Synthetic




Mechanical



Concentration




Electrical



Heat





Biolumine
scence


C.
Sources of energy



Photoautotrophs



Chemoheterotrophs


D. Energy flow through the biosphere



Oxidation

vs.

reduction



Energy flow is unidirectional



Flow of matter is cyclical

II.
Bioenergetics = applied thermodynamics


A.
System definition



System
v
s.

surroundings



Closed
vs.

open system


B.
1
st

Law of Thermodynamics
:
Law of conservation of energy



For open systems: total amount of energy leaving a system equals the amount of energy



entering the system minus the energy remaining (stored) in the
system



Internal energy, E



Enthalpy (heat content), H



Exothermic
vs.

endothermic


C.
2
nd

Law of Thermodynamics



Entropy


spontaneous

reactions tend toward greater entropy



Free energy (G)


a measure of spontaneity for a
system



Exergonic
vs.

endergonic



Equilibrium constant, K
eq




Standard free energy change,

G°’




G’ is the most useful measure of thermodynamic spontaneity

III.
Steady State


Equilibrium is never reached


Cells exist at a steady state AWAY from equilibrium