BIOENERGETICS
Energy Flow
1
What is Bioenergetics?
The study of
energy in living
systems
(environments)
and the
organisms
(plants and
animals) that
utilize them
2
Energy


Required by
all organisms
May be
Kinetic or
Potential
energy
3
Kinetic Energy


Energy of
Motion
Heat and
light energy
are
examples
4
Potential Energy


Energy of
position
Includes
energy
stored in
chemical
bonds
5
Two Types of
Energy Reactions
6
Endergonic Reactions



Chemical reaction that requires
a net input of energy.
Absorbs free energy and stores
it
Photosynthesis
SUN
photons
Light
Energy
6CO2 + 6H2O  C6H12O6 + 6O2
(glucose)
7
Exergonic Reactions


Chemical reactions that
releases energy
Cellular Respiration
Energy
C6H12O6 + 6O2  6CO2 + 6H2O+ ATP
(glucose)
8
Metabolic Reactions
of Cells
9
What is Metabolism?


The sum total
of the chemical
activities of all
cells.
Managing the
material and
energy
resources of
the cell
10
Two Types of Metabolism


Catabolic
Pathways
Anabolic
Pathways
11
Catabolic Pathway



Metabolic reactions which release
energy (exergonic) by breaking down
complex molecules in simpler
compounds
Hydrolysis = add a water molecule to
break apart chemical bonds
energy
Cellular Respiration
C6H12O6 + 6O2  6CO2 + 6H2O +
(glucose)
ATP
12
Anabolic Pathway



Metabolic reactions, which consume
energy (endergonic), to build
complicated molecules from simpler
compounds.
Dehydration synthesis = removal of a water
molecule to bond compounds together
Photosynthesis
SU
N
light
energy
6CO2 + 6H2O  C6H12O6 + 6O2
(glucose)
13
Energy Coupling



The transfer of energy from
catabolism to anabolism
Energy from exergonic reactions drive
endergonic reactions and vice versa
EX. Photosynthesis – cellular respiration
cycle
14
Energy Transformation

Governed by the Laws of
Thermodynamics.
15
1st Law of Thermodynamics


Energy can be transferred and
transformed, but it cannot be
created or destroyed.
Also known as the law of
Conservation of Energy.
16
2nd Law of Thermodynamics

Each energy transfer or
transformation increases the
entropy of the universe.
Entropy = a measure of
disorder or randomness
HEAT is energy in its most random state.
17
Summary

The quantity of energy in the
universe is constant, but its quality is
not.
18
Free Energy
The portion of a system's energy
that can perform work.
G = H - TS
G = free energy of a system
H = total energy of a system
T = temperature in oK
S = entropy of a system

19
Free Energy of a System

If the system has:





more free energy
it is less stable
It has greater work capacity
Metabolic equilibrium = zero free energy so it can do no
work
DEAD CELL
Metabolic disequilibrium = produces free energy to do
work


More unstable produces more free energy
EX. Greater concentration/ temperature differences
20
Free Energy Changes
21
Spontaneous Process


If the system is unstable, it has a
greater tendency to change
spontaneously to a more stable state.
This change provides free energy for
work.
22
Chemical Reactions


Are the source of energy for living systems.
Are based on free energy changes.
Reaction Types
Exergonic: chemical reactions with a net
release of free energy.
Endergonic: chemical reactions that
absorb free energy from the
surroundings.
23
Exergonic/Endergonic
24
3 main kinds of cellular work



Mechanical - muscle contractions
Transport - pumping across
membranes
Chemical - making polymers
All cellular work is
powered by
ATP
25
Cell Energy


Couples an exergonic process to drive
an endergonic one.
ATP is used to couple the reactions
together.
26
Cellular Energy ATP
27
ATP

Components:
1. adenine: nitrogenous base
2. ribose: five carbon sugar
3.phosphate group: chain of 3
adenine
phosphate group
P
P
P
ribose
28
Adenosine Triphosphate



Three phosphate
groups-(two with
high energy bonds
Last phosphate
group (PO4) contains
the MOST energy
All three phosphate
groups are
negatively charged
(repel each other
making it very
unstable)
29
Breaking the Bonds of ATP


Occurs continually in cells
Enzyme ATP-ase can
weaken & break last PO4
bond releasing energy &
free PO4
Phosphorylated = a
phosphate group
attaches to other
molecules making them
more unstable and more
reactive (energy boost to
do work)
30
How does ATP work ?


Organisms use enzymes to
break down energy-rich
glucose to release its
potential energy
This energy is trapped and
stored in the form of
adenosine triphosphate(ATP)
31
How Much ATP Do Cells Use?

It is estimated
that each cell
will generate
and consume
approximately
10,000,000
molecules of
ATP per second
32
Coupled Reaction - ATP

The exergonic
hydrolysis of ATP
is coupled with
the endergonic
dehydration
H2O
process by
transferring a
phosphate group
to another
H 2O
molecule.
33
Hydrolysis of ATP
ATP + H2O 
ADP + P
(exergonic)
Adenosine triphosphate (ATP)
P
P
P
Hydrolysis
(add water)
P
P
+
P
Adenosine diphosphate (ADP)
34
Hyrolysis is Exergonic
Energy
Used
by
Cells
35
Dehydration of ATP
ADP + P

(endergonic)
ATP + H2O
Dehydration
(Remove H2O
P
P
+
P
Adenosine diphosphate (ADP)
Adenosine triphosphate (ATP)
P
P
P
36
Dehydration is Endergonic
Energy
is
restored
in
Chemical
Bonds
37
ATP in Cells



A cell's ATP content is recycled
every minute.
Humans use close to their body
weight in ATP daily.
No ATP production equals quick
death.
38
What Are Enzymes?



Most enzymes are
Proteins (tertiary
and quaternary
structures)
Act as Catalyst to
accelerates a
reaction
Not permanently
changed in the
process
39
Enzymes



Are specific for
what they will
catalyze
Are Reusable
End in –ase
-Sucrase
-Lactase
-Maltase
40
How do enzymes Work?
Enzymes work by
weakening bonds
which lowers
activation energy
41
Activation Energy

Energy needed to convert potential
energy into kinetic energy.
Activation Energy
Potential Energy
42
Enzymes
Free
Energy
Without Enzyme
With Enzyme
Free energy of activation
Reactants
Products
Progress of the reaction
43
44
45
Enzyme-Substrate Complex
The substance (reactant) an
enzyme acts on is the
substrate
Substrate
Joins
Enzyme
46
Active Site
Active
Site
Substrate

Enzym
e
A restricted region of an enzyme molecule
which binds to the substrate.
47
48
Models of How Enzymes Work
1. Lock and Key model
2. Induced Fit model
49
Lock and Key Model

Substrate (key) fits to the active
site (lock) which provides a
microenvironment for the specific
reaction.
50
Induced Fit


A change in
the shape of
an enzyme’s
active site
Induced by
the substrate
51
Induced Fit Model

Substrate “almost” fits into the
active site, causing a strain on the
chemical bonds, allowing the reaction.
52
Enzymes


Usually specific to one substrate.
Each chemical reaction in a cell
requires its own enzyme.
53
Factors that Affect Enzymes





Environment (Temperature & pH)
Cofactors
Coenzymes
Inhibitors
Allosteric Sites
54
Environment


Factors that change protein
structure will affect an enzyme.
Examples:



pH shifts
temperature
salt concentrations
55
Temperature & pH
 High
temperatures denature
enzymes (Most enzymes like
normal body temperatures)
 Most enzymes function near
neutral pH (6 to 8)
 Denatured (unfolded) by
ionic salts
56
57
Cofactors



Inorganic substances (zinc, iron, copper)
are sometimes need for proper enzymatic
activity.
Non-protein helpers can bond to the
active site of enzymes to help in reactions
Example:
Iron must be present in the quaternary
structure of hemoglobin in order for it
to pick up oxygen.
58
Coenzymes


Organic molecules that act as
cofactors which help enzymes.
Examples:

vitamins
59
Two examples of Enzyme
Inhibitors
a. Competitive inhibitors: are
chemicals that resemble an
enzyme’s normal substrate and
compete with it for the active
site.
Substrate
Competitive inhibitor
Enzyme
60
Inhibitors
b. Noncompetitive inhibitors:
Inhibitors that do not enter the active
site, but bind to another part of the
enzyme causing the enzyme to change
its shape, which in turn alters the
active site.
Substrate
active site
altered
Enzyme
Noncompetitive
Inhibitor
61
62
Control of Metabolism


Is necessary if life is to function.
Controlled by switching enzyme activity
"off" or "on” or separating the enzymes in
time or space.
Types of Control
1. Switching on or off the genes that
encode for specific enzyme
production
2. Allosteric sites
3. Feedback inhibition
4. cooperativity
63
Allosteric Regulation




The control of an enzyme complex by the binding
of a regulatory molecule.
Regulatory molecule may stimulate or inhibit the
enzyme complex.
Allosteric site is a specific receptor site on some
part of the enzyme molecule away from the active
site
When activated, this site changes the shape of
the enzyme to inhibit it or to stimulate it
64
Allosteric Regulation
65
Feedback Inhibition



When a metabolic pathway is
switched off by its end-product.
End-product usually inhibits an
enzyme earlier in the pathway.
Prevents the cell from wasting
chemical resources
66
67
Cooperativity


One substrate molecule can trigger
the same favorable shape-change in
all the other subunits of the enzyme
Amplifies the response of the
enzymes to substrate
68
Review
69
How many high energy phosphate
bonds does ATP have?
70
Which is true of photosyntheis?
Anabolic
or
Catabolic
Exergonic
Or
Endergonic
71
The breakdown of ATP is
due to:
Dehydration
or
Hydrolysis
H2O added
or
H2O removed
72
Which Reactions are often
Coupled in Organisms
Hydrolysis
Anabolism
Endergonic
or
BOTH
Dehydration
or
Catabolism
or
Exergonic
BOTH
BOTH
73