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BIOLOGY
A GUIDE TO THE NATURAL WORLD
FOURTH EDITION
DAVID KROGH
Life’s Mainspring:
An Introduction to Energy
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6.1 Energy is Central to Life
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Energy is Central to Life
• All living things require energy.
• Sunlight - ultimate source of energy for most
living things.
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Energy is Central to Life
• Sun’s energy is captured by photosynthesizing
organisms (such as plants and algae),
• Which then pass this energy on to other
organisms in the form of food.
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings.
6.4 The Energy Dispenser: ATP
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The Energy Dispenser: ATP
• Adenosine triphosphate (ATP) - most important
energy transfer molecule in living things.
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ATP
• Energy extracted from food is transferred to
ATP
• Energy in ATP is used to drive metabolic
processes.
• Examples: to power muscle contraction and
nerve signal transmission.
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings.
The ATP/ADP Cycle
phosphate groups
adenine
adenosine
H2O
+
ribose
ATP
endergonic
reaction
energy
in
exergonic
reaction
energy
out
ADP
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings.
Figure 6.6
Energy and Biology
PLAY
Animation 6.1: Energy and Biology
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6.5 Efficient Energy Use in Living Things:
Enzymes
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Efficient Energy Use in Living Things:
Enzymes
• Enzyme - type of protein that speeds up a
chemical reaction
• Nearly every chemical process in living things
is facilitated by an enzyme
• Example: hemoglobin – a protein in blood cells
– Transfers oxygen from lungs to body cells
– Transfers carbon dioxide from body cells to lungs
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Enzyme Action
enzyme
A
enzyme
B
enzyme
C
substrates
product
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Figure 6.8
Metabolism and Enzymes
• metabolism - sum of all chemical reactions that
a cell or organism carries out
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6.6 Lowering the Activation Barrier through
Enzymes
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Enzymes Accelerate Chemical
Reactions
(a) Without enzyme
lactose
glucose + galactose
activation energy
without enzyme
net energy released
from splitting of
lactose
(b) With enzyme
lactase
lactose
glucose + galactose
activation energy
with enzyme
net energy released
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Figure 6.9
Substrate Binding
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Figure 6.10
Enzymes Overview
PLAY
Animation 6.2: Enzymes
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings.
Ch. 7-Vital Harvest:
Deriving Energy from Food
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7.1 Energizing ATP: Adding a Phosphate
Group to ADP
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Storing and Releasing Energy
2. Energy from food is then
stored as a phosphate bond
in ATP.
3. Energy is then released when
the phosphate bond is
broken, and can be used to
fuel our everyday activities.
1. Energy from food is
required to push a third
phosphate group onto ADP.
energy
in
ATP
energy
out
energy hill
P +
ADP
P +
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ADP
Figure 7.1
The Electron Carrier NAD+
empty
loaded
empty
goes to pick
up more electrons
proton
(oxidized)
used in later
stage of respiration
(reduced)
used in later
stage of respiration
1. NAD+ within a cell,
along with two hydrogen
atoms that are part of the
food that is supplying
energy for the body.
2. NAD+ is reduced to NAD
by accepting an electron from
a hydrogen atom. It also picks
up another hydrogen atom to
become NADH.
3. NADH carries the electrons
to a later stage of respiration
then drops them off,
becoming oxidized to
its original form, NAD+.
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Figure 7.3
Oxidation and Reduction
PLAY
Animation 7.1: Oxidation and Reduction
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings.
7.3 The Three Stages of Cellular
Respiration: Glycolysis, the Krebs Cycle,
and the Electron Transport Chain
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The Three Stages of Cellular
Respiration: Glycolysis, the Krebs
Cycle, and the Electron Transport
Chain
• In most organisms, the harvesting of energy
from food takes place in three principal stages.
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Cellular Respiration
•
•
Cellular respiration is making energy (ATP)
from food (glucose).
It has three stages:
1. Glycolysis
2. Krebs Cycle (Citric Acid Cycle)
3. Electron Transport Chain (ETC)
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Cellular Respiration
• Glycolysis takes place in the cell’s cytosol,
• Krebs cycle and ETC take place in
mitochondria
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Cellular Respiration
• Glycolysis yields two net molecules of ATP per
molecule of glucose, as does the Krebs cycle.
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings.
Cellular Respiration
Suggested Media Enhancement:
Cellular Respiration
To access this animation go to folder C_Animations_and_Video_Files
and open the BioFlix folder.
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings.
Cellular Respiration
• The net yield in the ETC is a maximum of
about 32 ATP molecules per molecule of
glucose.
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings.
Cellular Respiration
• Glycolysis and the Krebs cycle are critical in
that they yield electrons that are carried to the
ETC for the final high-yield stage of energy
harvesting.
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings.
Energy Harvesting
(b) In schematic terms
reactants
glycolysis
(a) In metaphorical terms
2 ATP
insert 1 glucose
glycolysis
products
glucose
2 NADH
2 energy
tokens
2 energy
tokens
Krebs
cycle
cytosol
glucose derivatives
CO2
2 NADH
CO2
6 NADH
Krebs
cycle
2 ATP
2 FADH2
32 energy
tokens
electron
transport
chain
electron
transport
chain
O2
32 ATP
mitochondrion
H2O
36 ATP maximum per glucose molecule
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Figure 7.4
7.4 First Stage of Respiration: Glycolysis
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Glycolysis
molecules in
molecules out
glycolysis
glucose
glucose
Krebs
cycle
electron
transport
system
glucose-6-phosphate
Red balls are
carbons and
gold ovals are
phosphate groups
fructose-6-phosphate
fructose-1,6-diphosphate
glyceraldehyde-3-phosphate
1,3-diphosphoglyceric acid
3-phosphoglyceric acid
pyruvic acid
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Figure 7.5
7.5 Second Stage of Respiration: The
Krebs Cycle
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Transition Between Glycolysis
and the Krebs Cycle
glycolysis
glucose derivatives
2 NADH
Krebs
cycle
electron
transport
chain
glycolysis
mitochondrion
pyruvic acid
cytosol
NAD+
NADH
coenzyme
A
to electron
transport
chain
CoA
acetyl coenzyme A
CO2
inner
compartment
Krebs
cycle
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Figure 7.7
The Krebs Cycle
• The net energy yield of the Krebs cycle per
molecule of glucose is:
– six molecules of NADH
– two molecules of FADH2
– two molecules of ATP
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings.
The Krebs Cycle
glycolysis
acetyl coenzyme A
Krebs
cycle
oxaloacetic acid
electron
transport
chain
1.
citric acid
2.
6.
a-ketoglutaric acid
malic acid
3.
5.
succinic acid
4.
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a-ketoglutaric
acid derivative
Figure 7.8
7.6 Third Stage of Respiration: The
Electron Transport Chain
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The Electron Transport Chain
glycolysis
Krebs
cycle
Mitochondrion
inner membrane
outer compartment
electron
transport
chain
H2O
O2
inner compartment
Electron transport chain
ATP synthesis
outer compartment
inner
membrane
NAD+
1
2 H+ + —
O2
2
H2O
ATP
synthase
inner compartment
ADP + P
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Figure 7.9
7.7 Other Foods, Other Respiratory
Pathways
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Many Respiratory Pathways
food
proteins
carbohydrates
fats
amino acids
sugars
glycerol fatty acids
glucose
glycolysis
pyruvic acid
acetyl CoA
Krebs
cycle
NH3
(ammonia)
electron
transport
chain
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings.
Figure 7.10