Topic 5: Bioenergetics

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Topic 5 Bioenergetics
Protonmotive force
ATP
Electron transfer reactions
Respiration
Mitochondria chloroplasts
Other examples
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Reading for Topic 5

• Alberts Chapters 2, 11,14
• Nelson Chapters 11

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Photosynthesis
Respiration
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An overview of bioenergetics Free Energy flow in
living things
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Covered in this topic
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Protonmotive Force (pmf)
Vm is the electrical potential (defined as free
energy per unit charge) Dm is the chemical
potential (defined as free energy see topic 4)
Typically, pmf is in the range -150 mV to -200 mV
Usually both components are negative Inside
has lower voltage and lower H
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Light or Chemical reactions
H
Vm Dm /e protonmotive force
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Proton pumping
























H
H
H
H
H
H
H
H
H
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food eg) glucose
electrons
ATP
reproduction
ATP
pmf
photons
growth
transport
movement
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Respiration
food eg) glucose
electrons
reproduction
photons
ATP
pmf
growth
transport
movement
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pmf
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NAD(P) nicotinamide adenine dinucleotide
(Phosphate)
NADH
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Electron-transfer or REDOX reactions
Reduction (gain electrons)
Standard reduction potential (V)
Half reactions
1.
-0.315
-0.166
2.
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Measuring (biochemists) standard redox potentials
10-7 M H 1M NAD 1M NADH
10-7M H 1atm H2
NAD 2e- 2H NADH Standard potential
-0.315V reaction proceeds in reverse
2e- 2H H2 Standard potential 0V
(By definition, this is the reference reaction)
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Reduction of B
Oxidation of BH
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food eg) glucose
electrons
ATP-Synthase
reproduction
pmf
ATP
photons
growth
transport
movement
 
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Free Energy Accountancy
Approximate free energies DG(each) DG(total)
Glucose 1160 1160 NADH 25 250 H(pmf)
8 800 ATP 25 950 Standard free
energy. The actual value in mitochondria is
similar, as the concentrations of NADH and NAD
are the same to within an order of magnitude or
so, and the pH is close to 7.
1 glucose
38 ATP
8 ATP
30 ATP
10 NADH plus other high-energy molecules
100 H
(pmf)
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food eg) glucose
electrons
reproduction
pmf
ATP
photons
growth
transport
movement
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electrons
food eg) glucose
reproduction
pmf
ATP
photons
growth
transport
movement
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