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UNIT 2
Lecture 6
Metabolism
Unit 2:
Life’s Energy Sources and Conversions
• Metabolism
• Cellular Respiration: Sugar  ATP
• Photosynthesis: Light  Sugar
Key Themes
• Energy acquisition & conversions in metabolism
The Molecules of Life
Structure-Function Relationship
Life’s Energy Conversions
Metabolism
An organism’s metabolism is the total of the
organism’s chemical reactions
•Two types of reactions:
– Big molecule
Several small molecules
• Releases energy
– Small molecules
• Requires energy
Big molecule
Metabolism
An organism’s metabolism is total of the
organism’s chemical reactions
•Two types of reactions:
– Big molecule
Several small molecules
• Releases energy
• This sounds like:
a) Cellular respiration
b) Photosynthesis
c) Neither
Order and Chaos
Energy
Nature “wants” to be random/chaotic
Energy
Mydesigningsolutions.com; bedroomdisaster.blogspot.com; fritolay.com; slashfood.com
Order and Chaos
A complex,
ordered
molecule
Energy
Several small,
disordered
molecules
Nature “wants” to be random/chaotic
A complex,
ordered
molecule
Energy
Mydesigningsolutions.com; bedroomdisaster.blogspot.com; fritolay.com; slashfood.com
Several small,
disordered
molecules
CO2
Glucose
Requires
Energy
Releases
Newenergyandfuel.com; ualberta.ca; all-water.org
H2O
Fig. 8-6
Reactants
Energy
Amount of
energy
released
Energy
Products
Progress of the reaction
(a) Energy-releasing reactions
Products
Energy
Amount of
energy
required
Energy
Reactants
Progress of the reaction
(b) Energy-requiring reactions
Fig. 9.2
Light
Ecosystem
energy
energy flow ECOSYSTEM
ATP
Photosynthesis
in chloroplasts
Organic + O
CO2 + H2O
2
molecules
Cellular respiration
in mitochondria
ATP
ATP then powers cellular work
Heat
energy
1. Be able to
link
producers
and
consumers
via cycles of
energy and
carbon flow
Light
energy
ECOSYSTEM
ATP
Photosynthesis
in chloroplasts
Organic + O
CO2 + H2O
2
molecules
Cellular respiration
in mitochondria
ATP
Fig. 9.2
Energy flow
in ecosystems
ATP then powers cellular work
Heat
energy
1. Be able to
link
producers
and
consumers
via cycles of
energy and
carbon flow
Light
energy
ECOSYSTEM
ATP
Photosynthesis
in chloroplasts
Organic + O
CO2 + H2O
2
molecules
Cellular respiration
in mitochondria
ATP
Fig. 9.2
Energy flow
in ecosystems
ATP then powers cellular work
Heat
energy
Chaos = Entropy
CO2
Glucose
H2O
Requires
Energy
Releases
Low Entropy System
(less random, more ordered)
High Entropy System
(more random, less ordered)
Newenergyandfuel.com; ualberta.ca; all-water.org
CO2
Glucose
Requires
Energy
Releases
Potential energy is stored in
chemical bonds (C-H especially)
Newenergyandfuel.com; ualberta.ca; all-water.org
H2O
Heat
Chemical
energy
CO2
+
H2O
Cells’ ability to store energy in chemical bonds is
what makes organisms and ecosystems function
Heat
Chemical
energy
CO2
+
H2O
Cells’ ability to store energy in chemical bonds is
what makes organisms and ecosystems function
Without
photosynthesis…
There is no way
to convert light
energy into
chemical energy
Heat
Chemical
energy
CO2
+
H2O
What about cellular respiration?
Without cellular respiration:
A. Nothing could live
B. No animals could live
C. Nothing nonphotosynthetic could live
D. Everything could live
Where does energy go?
Where does energy go in an
ecosystem?
• Heat, growth, reproduction, etc.
Heat
Heat
Heat
Heat
Trophic levels: Energy Flow Through Ecosystem
http://www.britannica.com/EBchec
ked/media/15/Transfer-of-energythrough-an-ecosystem
5 minute break
A cell (in any organism) constantly
performs work that requires energy:
Energy for all cellular work is provided by the
same energy-rich compound:
ATP (adenosine triphosphate)
Fig. 8.8
ATP
ATP consists of three phosphate groups, a sugar, and a
nitrogenous base.
What does that sound like?
A) a triglyceride
B) a nucleotide
C) a phospholipid
D) a trisaccharide
Each nucleotide is composed of:
a monosaccharide sugar, a phosphate group,
and a (N-containing) nitrogenous base
Nitrogenous
base
A = adenine
A + Ribose = adenosine
adenosine mono-phosphate (AMP)
adenosine di-phosphate (ADP)
adenosine tri-phosphate (ATP)
Phosphate
Sugar
group
(b) Nucleotide
Fig. 5.27
Fig. 8.8
ATP takes the energy released from the
breakdown of energy-rich food molecules
and does cellular work
Energy loaded onto
ATP
Energy from
breakdown of
energy-rich
molecules
ATP + H2O
Fig. 8.12
Energy released from
ATP
Energy for cellular
work
ADP + P i
Fig. 8-9
P
P
P
Adenosine triphosphate (ATP)
H2O
Pi
+
Inorganic phosphate
P
P
+
Adenosine diphosphate (ADP)
Energy
ATP: Energy carrier
Higher
Energy
Fig. 8.8
“Phosphorylated”
(=energized!)
molecule
+
Lower
Energy
High-energy P transferred to motor proteins
for mechanical work
ADP
+
ATP
P
Vesicle
Cytoskeletal track
i
ATP
Motor protein
Protein moved
ATP transfers phosphate group to motor protein
(phosphorylated motor protein = energized)
Fig. 8.11 (b)
See Campbell Figures 50.27 & 50.29 for additional details on muscle contraction.
High-energy P transferred to transport proteins
for transport work
Membrane protein (Na+/K+ pump)
P
Na+
P
i
Na+ moved uphill
ADP
ATP
Fig. 8.11 (a); see also Fig. 7.16 for more detail
+
P
i
Na+/K+ Pump
Na+
ATP
K+
• Cells want to pump Na+ out
• Cells want to pump K+ in
8. Be able to apply the principal features and functions
of an ATP-fueled ion pump to the Na+/K+ pump
Active transport and
the sodium-potassium pump
Both Na+ and K+ are moved
AGAINST their concentration gradient
See Fig. 7.16 for a six panel, blow-by-blow
description of the sodium-potassium pump.
http://www.colorado.edu/ebio/genbio/07_16ActiveTransport_A.html
http://onlinephys.com/circuit1.html
Fig.8.7
http://onlinephys.com/circuit1.html
Cotransport: Using potential energy
Na+
ATP fuels the Na+/K+ pump
Na+ accumulates “on top of the hill”
(against its concentration gradient)
Na+ flows downhill again
ATP
Releasing useful energy
Cotransport: Using potential energy
Na+
ATP fuels the Na+/K+ pump
Na+ accumulates “on top of the hill”
(against its concentration gradient)
POTENTIAL ENERGY
Na+ flows downhill again
ATP
Releasing useful energy
35
Cotransport: Using potential energy
This potential energy
can be used…
To transport other molecules
AGAINST their concentration
gradient
The Na+ gradient built up by the Na+/K+ pump
also fuels the secondary active transport
of glucose (& other substances)
AGAINST their concentration gradient
In Na+/glucose co-transport, Na+
flows back downhill & drags glucose
uphill AGAINST its concentration
gradient
What provides the energy for the uphill
transport of Na+ against its concentration
gradient?
A)No energy is needed.
B)the Na+/K+ transport protein itself
C)ADP and Pi
D)ATP
What provides the energy for the
Na+/glucose cotransporter?
A)No energy is needed.
B)the Na+ gradient
C)ATP as a direct energy source
D)ATP as an indirect energy source
E)B and D
High-energy P transferred to transport proteins
for transport work
Membrane protein (Na+/K+ pump)
P
Na+
P
i
Na+ moved uphill
ADP
ATP
+
Fig. 8.11 (a); see also Fig. 7.16 for more detail
41
P
i
High-energy P transferred to reactant
molecules for chemical work
(ATP adds phosphate
group to glutamic acid,
making it less stable.)
P
+
Glu
ATP
Glu
+ ADP
NH2
(Ammonia displaces
phosphate group,
forming the amino acid
glutamine.)
Fig. 8.10 (b)
P
Glu
+
NH3
+ P
Glu
i
Summary: To stay alive, living cell performs 3
kinds of work that require energy:
1. Mechanical work
2. Transport work
3. Chemical work
Energy for all 3 types of work provided by:
ATP (adenosine triphosphate)
• ATP is too unstable to serve as an actual
storage form of energy.
• Therefore, C-H bonds in macromolecules (e.g.
sugars) are instead used for energy storage.
Since ATP is too unstable,
C-H bonds in sugars are used for energy storage.
Converts solar energy
to ATP and uses ATP to
make sugars
Photosynthesis:
Light (energy)
CO2 + H20
ATP
Sugar [CH2O]x +
O2
ATP
Respiration:
Converts the energy of sugars back to ATP
as needed.
Hank’s crash course in ATP
0-3:30
http://www.youtube.com/watch?v=00jbG_cfGuQ&feature=relmfu
Key Themes
(2) “Think Like a Biologist”: Understand What Life Is.
“Unity” of life: What are common features of eukaryotes?
Energy conversions:
Sugar breakdown & mitochondrial ATP formation
Fig. 9.1
Respiration
Food-to-Energy
Fig. 8.3
Cellular respiration breaks down energy-rich
molecules to CO2 & water, extracting their energy.
Light
energy
ECOSYSTEM
Low
energy
Photosynthesis
in chloroplasts
CO2 + H2O
Cellular respiration
in mitochondria
Organic+ O
molecules 2
High
energy
C-H bond!
ATP
ATP powers most cellular work
Heat
energy
“burned” with
O2 to form
H2O + CO2
Fig. 9.2
Since ATP is too unstable,
C-H bonds in sugars are used for energy storage.
Converts solar energy
to ATP and uses ATP to
make sugars
Photosynthesis:
Light (energy)
CO2 + H20
ATP
Sugar [CH2O]x +
O2
ATP
Respiration:
Converts the energy of sugars back to ATP
as needed.
Today’s Exit Ticket
• In a few sentences:
– Describe energy-releasing and energyrequiring reactions.
– Use the creation and use of ATP for cellular
work as examples of these reactions.
– Be sure to use the word “entropy.”