Download Energy Ch6

Chapter 6
• Energy Flow in the Life of a Cell
Copyright © 2005 Pearson Prentice Hall, Inc.
Energy?
• ABILITY TO DO WORK
– potential (stored) kinetic (active)
(the diver illustration)
• “Acts” According to 2 “Rules”
– First Law of Thermodynamics
Energy Cannot be Created or Destroyed OR
Energy Can Only be Converted from 1 Form to Another
OR
“YOU CAN’T WIN”
– Second Law of Thermodynamics
Every Process Generates Some Unusable Energy (= Heat)
Every System “Wants” To Get To Its Lowest Energy State
OR
“YOU CAN’T BREAK EVEN”
OR
• Organisms Are Organized = High Energy State
– 2nd Law Constantly “Driving Them Down”
– Therefore Organisms Constanly Use Energy to Stay Organized
Copyright © 2005 Pearson Prentice Hall, Inc.
Energy?
• ABILITY TO DO WORK
– potential (stored) kinetic (active) Unnumbered
(diver)
• “Acts” According to 2 “Rules”
– First Law of Thermodynamics
Energy Cannot be Created or Destroyed
Energy Can Only be Converted from 1 Form to Another
“YOU CAN’T WIN”
– Second Law of Thermodynamics
Every Process Generates Unusable Energy (= Heat)
Every System “Wants” To Get To Its Lowest Energy State
“YOU CAN’T BREAK EVEN”
• Organisms Are Organized = High Energy State
– 2nd Law Constantly “Driving Them Down”
– Therefore Organisms Constanly Use Energy to Stay Organized
Copyright © 2005 Pearson Prentice Hall, Inc.
gas
100 units
chemical
energy
(concentrated)
75 units heat
energy
25 units kinetic energy
(motion)
How Do Organisms Constantly Use Energy
to Stay Organized?
• By Reaction Coupling
2 Types of Reactions:
– Exergonic – Release Energy
– Endergonic – Take In Energy
– Energy relations in exergonic and endergonic reactions
– Organisms Use the Energy of Sunlight to Maintain The
Highly Organized (=Low-Entropy) Condition Known as Life
• Carry Out Reaction Coupling By Energy Carriers:
Copyright © 2005 Pearson Prentice Hall, Inc.
Exergonic reaction
energy
released
reactants
products
Endergonic reaction
energy
used
products
reactants
Burning glucose
energy
released
6 O O
glucose
oxygen
6 O C O
carbon
dioxide
6 H
O
H
water
Photosynthesis
energy
6 O O
6 O C O
carbon
dioxide
6 H
glucose
O
H
water
oxygen
Burning glucose (sugar): an exergonic reaction
high
Photosynthesis: an endergonic reaction
high
activation energy needed
to ignite glucose
energy
content
of
molecules
glucose + O2
energy released
by burning glucose
energy
content
of
molecules
CO2 + H2O
low
activation
energy from
light captured
by photosynthesis
CO2 + H2O
low
progress of reaction
progress of reaction
glucose
net energy
captured by
synthesizing
glucose
Exergonic reaction:
ATP
100 units
ADP
energy released
P
80 units energy ADP
released as heat
P
Endergonic reaction:
20 units
energy
contracted
muscle
relaxed
muscle
Coupled reaction:
ATP
relaxed
muscle
contracted
muscle
Exergonic reaction:
+ ADP
100 units
energy released
ATP
+
P
ADP +
P
Endergonic reaction:
+
20 units
energy
contracted
muslce
relaxed
muscle
Coupled reaction:
+
relaxed
muscle
+ 80 units energy +
released as heat
ATP
contracted
muslce
6.3 How Is Cellular Energy
Carried Between Coupled
Reactions?
• 6.3.1 ATP Is the Principal Energy Carrier
in Cells
– Figure 6.4 ADP and ATP (p. 104)
– Unnumbered Figure 6 (Hide/Reveal) ATP
synthesis: Energy is stored in ATP (p. 104)
– Unnumbered Figure 7 (Hide/Reveal) ATP
breakdown: Energy of ATP is released (p. 104)
– Figure 6.5 Coupled reactions within living cells
(p. 105)
Copyright © 2005 Pearson Prentice Hall, Inc.
Adenosine triphosphate (ATP)
Adenosine diphosphate (ADP)
NH2
adenine
N
C
C
NH22
"high-energy”
bond
N
N C C
N
N C
CH
"high-energy”
bonds
HC
HC
N
C
N
CH
O–
O
CH2
ribose
H
H
H
OH
OH
Shorthand
representations
A
Energy
content
O
P
H
O–
H
O
phosphate groups
low
P
or
ADP
A
H
H
OH
OH
P
O–
O–
O
P O–
O
O
P
N
O
CH2
H
P
O
O
P
O
O–
O
P O–
O
phosphate groups
P
P
high
or
ATP
Adenosine diphosphate (ADP)
NH2
adenine
N C C
N
N C
CH
"high-energy”
bond
HC
N
O–
O
CH2
H
ribose
H
Shorthand
representations
Energy
content
H
H
OH
OH
A
O
P
O–
P O–
O
O
O
phosphate groups
P
low
P
or
ADP
Adenosine triphosphate (ATP)
NH2
N C C
"high-energy”
bonds
N
HC
N C N CH
O
H
A
H
H
OH
OH
P
O–
O–
O
CH2
H
P
O
O
P
O
O–
O
P O–
O
phosphate groups
P
P
high
or
ATP
ATP synthesis: Energy is stored in ATP
energy
A
A
P
ADP
P
P
phosphate
P
ATP
P
P
ATP synthesis: Energy is stored in ATP
energy
A
A
P
ATP
P
ADP
P
P
phosphate
P
P
ATP breakdown: Energy of ATP is released
energy
A
P
P
P
ATP
A
P
ADP
P
P
phosphate
ATP breakdown: Energy of ATP is released
energy
A
P
P
P
ATP
A
P
ADP
P
P
phosphate
Coupled reaction: glucose breakdown and protein synthesis
glucose
A
exergonic
(glucose
breakdown)
P
P
P
protein
endergonic
(ATP synthesis)
exergonic
(ATP breakdown)
endergonic
(protein synthesis)
CO2 + H2O + heat
A
P
P
P
ADP
net exergonic
"downhill" reaction
heat
amino
acids
6.3 How Is Cellular Energy
Carried Between Coupled
Reactions?
• 6.3.2 Electron Carriers Also Transport
Energy Within Cells
– Figure 6.6 Electron carriers (p. 105)
Copyright © 2005 Pearson Prentice Hall, Inc.
Electron carrier molecules transport energy
NADH
exergonic
reaction
_
(energized
carrier)
e
_
e
(depleted
carrier)
NAD+
H
net exergonic
"downhill" reaction
endergonic
reaction
6.4 How Do Cells Control
Their Metabolic Reactions?
• Figure 6.7 Simplified view of metabolic
pathways (p. 106)
Copyright © 2005 Pearson Prentice Hall, Inc.
Initial reactant
PATHWAY 1
A
D
C
B
enzyme 1
Final products
Intermediates
enzyme 2
enzyme 3
PATHWAY 2
E
enzyme 4
F
enzyme 5
G
enzyme 6
6.4 How Do Cells Control
Their Metabolic Reactions?
• 6.4.1 At Body Temperatures,
Spontaneous Reactions Proceed Too
Slowly to Sustain Life
• 6.4.2 Catalysts Reduce Activation
Energy
– Figure 6.8 Catalysts lower activation
energy, increasing the rate of reactions
(p. 106)
Copyright © 2005 Pearson Prentice Hall, Inc.
high
activation energy
without
catalyst
energy
content
of
molecules
activation energy
with catalyst
reactants
products
low
progress of reaction
6.4 How Do Cells Control
Their Metabolic Reactions?
• 6.4.3 Enzymes Are Biological Catalysts
• 6.4.4 The Structure of Enzymes Allows
Them to Catalyze Specific Reactions
– Figure 6.9 The cycle of enzyme–substrate
interactions (p. 107)
Copyright © 2005 Pearson Prentice Hall, Inc.
substrates
active site
of enzyme
enzyme
substrates
active site
of enzyme
enzyme
6.4 How Do Cells Control
Their Metabolic Reactions?
• 6.4.5 Cells Regulate the Amount and
the Activity of Their Enzymes
– Figure 6.10 Enzyme regulation by
feedback inhibition (p. 108)
– Figure 6.11 Enzyme regulation by
allosteric regulation and competitive
inhibition (p. 109)
Copyright © 2005 Pearson Prentice Hall, Inc.
CH3
CH3
H
C OH
H
C NH3
CH2
A
B
enzyme 1 enzyme 2 enzyme 3
C
D
enzyme 4
COOH
threonine
(substrate amino acid)
enzyme 5
H C CH3
H C
NH3
COOH
Feedback inhibition:
Isoleucine inhibits enzyme 1
isoleucine
(end-product amino acid)
Enzyme
structure
substrate
active site
enzyme
allosteric
regulatory site
Allosteric
inhibition
Competitive
inhibition
allosteric
regulator
molecule
Enzyme
structure
substrate
active site
enzyme
allosteric
regulatory site
Allosteric
inhibition
Competitive
inhibition
allosteric
regulator
molecule
6.4 How Do Cells Control
Their Metabolic Reactions?
• 6.4.6 The Activity of Enzymes Is
Influenced by Their Environment
Copyright © 2005 Pearson Prentice Hall, Inc.