Download Document

Energy: the capacity to effect change
BCOR 011
Lecture 11
Two types of energy
Chapter 8
The Flow of Energy in a Cell
Sept 26, 2005
Potential Energy
Kinetic Energy
-stored in height
-energy of movement
-stored in battery (conc/charge)
-stored in BONDS
-molecules colliding, vibrating
-HEAT, light
1
2
Figure 8.1
1st Law of Thermodynamics
Potential Energy Stored in:
Figure 8.2
location
Energy is neither created nor destroyed in
chemical reactions
but only Transformed from one form to another
Figure 8.5
On the platform, a diver
Diving converts potential
has more potential energy. energy to kinetic energy.
Chemical
bonds
Potential
Potential
Kinetic
Kinetic
gradient
Climbing up converts kinetic
energy of muscle movement
to potential energy.
In the water, a diver has
less potential energy.
3
4
In a chemical reaction
products have a lower potential energy than reactants
a Chemical Reaction
Atoms bonded in
High Potential Energy
Configuration
Example
- -
Energy is Released
H
H-C-H
H
Atoms bonded in
Low Potential Energy
Configuration
Reorganization of Bonds of existing molecules
- an exchange
O=C=O
O=O
H
O=O
Same # of H’s
Same # of C’s
Same # of O’s
O
H
H
H
-
H-C-H
H
6
Energy that is released:
reduced
Has the capacity to DO WORK
O=O
Raise potential state of something else
O=C=O
H
O
H
ENERGY
RELEASED
Or effect movement – heat, motion
oxidized
Low Energy
7
H
All Start with filled outer shell of electrons
All End with outer shell of electrons
5
High Energy
O
8
Other Types of Work
Types of Work:
1
Biosynthetic: changes in chemical bonds
A + B
2. Chemical Concentration Gradient
C + D
products
reactants
A+B
G+H
E+F
C+D
Ainside + Boutside
even
even
even
low
high
9
3. Electrical work – movement of ions across
a membrane against an electrochemical gradient
Ainside + Boutside
even
Aoutside + Binside
10
Other Types of Work
Aoutside + Binside
+
-
11
4
Mechanical Work: Movement, Motility
12
• Some organisms
Another form of
MOVEMENT
Relaxed
Low Energy
Conformation
A
– Convert energy to light, as in bioluminescence
Conformation
B
Poised
13
High Energy
Figure 8.1
Change
In potential
Energy
Energy that is released:
State 1
Has the capacity to DO WORK
Raise potential state of something else
Or effect movement – heat, motion
But some is always lost to disorder
State 2
Gross Pay
15
14
Released Energy
Ability
To do + Randomness
work
Take
Home +
Pay
Taxes
16
Kinetic Energy can be dissipated:
Second law of Thermodynamics:
Randomized
Releases Energy
Kinetic Energy
Ch
an
ce
of
Sound
Floor Vibration
go
ing
in
RE
Requires
Energy Input
VE
RS
E?
Disorder
The Universe is proceeding to a
State of MAXIMUM DISORDER
Only time this is not true
is when no movement anymore
ie. at abosolute zero
17
18
Change
In potential
Energy
0o K - no motion, no “taxes”
State 1
A Progressive Scale:
Higher the temperature,
the more that disorder comes into play
higher proportion of energy lost to randomness
19
State 2
Enthalpy
∆H
Released Energy
Ability
To do + Randomness
work
Free
Energy +
∆G
Entropy
T ∆S
20
ENTROPY
∆S
(disorder)
ENTHALPY
∆H
Change in
Chemical Bond
Energy
Freedom of
Movement
or
Position
Time
21
Number of
possible states
that can be
present in:
Change in
Freedom
Roll of “2”
High
Potential
High
Potential
Randomness
ENTROPY
∆S
Change in
Chemical Bond
Energy
ENTHALPY
∆H
Low entropy
Only 1 possible
“state”
Low Potential
Glucose
+
6 O2
6 CO2
+
6 H2O
ENTROPY
∆S
Few
States
Low Potential
6 Glucose 6 CO2
+
+
6 O2
6 H2O
Change in
Freedom
Many
States
“Dispersed”
22
Number of
Possible States
That can be
Present in
Few
States
Many
States
“Dispersed”
time
Roll of “7”
High entropy
-∆H
6 possible
“states”
23
Na+ ClNaCl
crystal ions in water
Na+ ClNaCl
crystal ions in water
+∆S
24
Change in
Chemical
Bond
Energy
The Free Energy Change
∆G
Dictates whether a reaction will
Proceed spontaneously or not
Energy that
Goes to
Do Useful Work
Energy that
Goes to
Randomness
Dependent
On
Entropy
Temperature
Enthalpy
“free energy”
(Gibb’s Free Energy)
Kinetic Movement
Whether a Reaction is
∆H
Favorable or Unfavorable
=
T∆S
∆G
25
=
+
∆H -
If ∆G = negative #
reaction is energetically favorable
∆G
T∆ S
“spontaneous”
26
An exergonic reaction
– Proceeds with a net release of
free energy and is spontaneous
“will happen”
Reactants
Free energy
Amount of
energy
released
(∆G <0)
Energy
Products
∆G = ∆H – T∆S
- ∆G is favorable exergonic “spontaneous”
+ ∆G is NOT favorable, endergonic,
endergonic, nonspontaneous27
Progress of the reaction
28
Figure 8.6 (a) Exergonic reaction: free
energy released
An endergonic reaction
2 Factors Contribute to Whether a Reaction will Occur:
– Is one that absorbs free energy from its
surroundings and is nonspontaneous
change in Bond Energy
“doesn’t happen”
Reduced
change in Entropy
Complex
Free energy
Products
Amount of
energy
released
(∆G>0)
Energy
Oxidized
Reactants
The sum of these is the
Progress of the reaction
Figure 8.6
Complex
change in Entropy
Lower
8
fats
H
H-C-H
H
H
R-C-OH
H
alcohol
30
EXERGONIC REACTIONS
gasoline burns
iron rusts
hydrogen and oxygen form water (explosive!)
Either: go to bonding arrangement with lower potential energy
O
=
sugars
R-C-H
aldehyde
O
=
change in Bond Energy
hydrocarbon
net ENERGY RELEASED - EXERGONIC = FAVORABLE
If require net ENERGY INPUT - ENDERGONIC = UNFAVORABLE
Simple
Reduced (no oxygens)
H H HHH HH H
H-C-C-C-C-C-C-C-C-H
H HH HH HH H
Net Useful Energy (∆
(∆G)
If
(b) Endergonic reaction: energy required
29
High
Simple
R-C-OH
Final
product
acid
Or: go from a more complex state to a simpler state
1 molecule of 8 carbons
vs
8 molecules of 1 carbon
O=C=O
Low
Oxidized
Carbon
31 dioxide
Lowest
32
∆H=
∆S=
+
∆G= very -
favorable
favorable
favorable
2
Spontaneous
33
Favorable - it can happen
∆H=
∆S=
∆G=
Unfavorable
+
+ Very favorable
favorable
Entropy Driven Reaction
Spontaneous
Favorable - it can happen 35
Entropy overwhelms Enthalpy
∆H = Hproducts -Hreactants
− ∆H
exothermic
Heat released
+ ∆H
endothermic
Heat input
icepack
34
∆H=
∆S=
∆G=
-
very favorable
unfavorable
favorable
Enthalpy Driven Reaction
Spontaneous
Favorable - it can happen
36
Enthalpy overweighs Entropy
∆H=
∆S=
∆G=
∆G = ∆H – T∆S ∆G = ∆H – T∆S ∆G = ∆H – T∆S
(-) - (+) (- ) - (- ) (+) - (+)
Spontaneous
Enthalpically
Entropically
37
Favorable Rxn
Driven Rxn
Driven Rxn
A typical
ENDERGONIC/Unfavorable/NonSpontaneous REACTION
- building a polymer
Monomer + Monomer
+
+
unfavorable
unfavorable
unfavorable
Non-spontaneous
NOT Favorable - it can NOT happen
38
COUPLED Reactions
Tie a favorable rxn with
An otherwise unfavorable rxn
Polymer + Water
Requires 5.5 energy units
WILL NOT OCCUR
How could we make it occur?
If have a captured packet of energy of 7.3 energy units
Integrate
an exergonic reaction with an endergonic reaction
39
Drive otherwise unfavorable
reactions
40
∆G = +5.5
kcal/mole
1.
2. ATP+ H2O
ADP + Pi
ATP
∆G = -7.3
kcal/mole
ADP + Pi
Favorable or unfavorable41 ?
Coupled Reaction
ADP -P
(ATP)
Note:
Each step is
favorable
∆G = -7.3 kcal/mole
+∆G = +5.5 kcal/mole
Net rxn ∆G = -1.8 kcal/mole
42
Another Example of a Coupled Reaction
+ monomer1
ADP-monomer1
+ P
Endergonic reaction: ∆G is positive, reaction
is not spontaneous
I’m free!
∆G = -1.0
ADP-monomer1 + monomer 2
NH2
Now tied together
Glu
ADP
+
Glutamic
acid
monomer1-monomer 2
Now I’m free too!
∆G = -0.8
7.3 units released
Net: ATP +H2O
monomer1 + monomer2
5.5 units needed
+
NH3
Glu
Ammonia
Glutamine
∆G = +3.4 kcal/mol
Exergonic reaction: ∆ G is negative, reaction
is spontaneous
ATP
ADP + P
monomer1-monomer2 + H2O
DO NOT LET ATP FALL APART IN 1 STEP,
use energy in its bond to MAKE the polymer linkage
43
Figure 8.10
+ H2 O
ADP +
Coupled reactions: Overall ∆G is negative;
together, reactions are spontaneous
P
∆G = + 7.3 kcal/mol
∆G = –3.9 kcal/mol
44
Three types of cellular work powered by
ATP hydrolysis
Physical
movement
P
Equilibrium
Reactions in a closed system
i
P
Motor protein
Driving
Conformational
Changes
ADP
Of
+
P
Proteins
Protein moved
(a) Mechanical work: ATP phosphorylates motor proteins
Membrane
protein
ActiveATP
Transport
Pumps
– Eventually reach equilibrium
∆G < 0
∆G = 0
i
P
Solute
P
i
Solute transported
(b) Transport work: ATP phosphorylates transport proteins
P
Glu +
NH2
NH3
Reactants: Glutamic acid
and ammonia
Figure 8.11
+
P
Glu
i
Product (glutamine)
made
Biosynthetic
Coupled
Rxn45
Figure 8.7 A
(a) A closed hydroelectric system. Water flowing downhill turns a turbine
that drives a generator providing electricity to a light bulb, but only until
the system reaches equilibrium.
46
(c) Chemical work: ATP phosphorylates key reactants
In living systems
cellular respiration is a series of favorable reactions
– Experience a constant flow of materials in
– Constant Energy Input
∆G < 0
∆G < 0
∆G < 0
∆G < 0
(b) An open hydroelectric
system. Flowing water
keeps driving the generator
because intake and outflow
of water keep the system
from reaching equlibrium.
Figure 8.7
Figure 8.7
47
(c) A multistep open hydroelectric system. Cellular respiration is
analogous to this system: Glucoce is brocken down in a series
of exergonic reactions that power the work of the cell. The product
of each reaction becomes the reactant for the next, so no reaction
reaches equilibrium.
48
Summary:
For example, oxidation of glucose:
C6H12O6 (glucose) + 6O2
6CO2 + 6H2O
-matter is neither created nor destroyed
-the universe is proceeding toward disorder
∆G= -686 kcal/mol
∆H = -673 kcal/mol
∆H = enthalpy (heat content,bond energy)
T∆S= -13 kcal/mol
∆S = entropy (randomness)
in the cell, this is done in >21 steps!
∆G = free energy (available to do work)
Capture the energy in small packets
∆G = ∆H - T∆S
ie, 36 ATP units of 7.3 kcal
- coupled reactions
49
-biological systems always need
constant energy input
50