Biological Energy
Generating biological free energy
by Richard Berry
http://www.mrc-mbu.cam.ac.uk/category/slideshows/atpmovies
Slide 1: The mechanism by which cells convert energy from light and food into
energy stored in ATP is based on membranes; most ATP is made using the free
energy of pmf by ATP-synthase. (Movie © Medical Research Council, used by
kind permission of John Walker.)
“food”
e.g. glucose
electrons
reproduction
photons
pmf
ATP
growth
transport
movement
Slide 2: Generating ATP by charging and discharging a membrane capacitor.
(Images bottom left and bottom right copyright © 2002 from Molecular Biology of
the Cell by Alberts et al. Reproduced by permission of Garland Science/Taylor &
Francis Books, Inc.)
The mitochondrion
Slide 3: Mitochondria. (Images courtesy of Daniel S Friend, taken from
Molecular Biology of the Cell by Alberts et al. copyright 2002 Garland
Science/Taylor & Francis Books, Inc.)
Respiration
“food”
eg) glucose
electrons
reproduction
photons
pmf
ATP
growth
transport
movement
Burning glucose:
ΔG0’ = –1160 kBT
Slide 4: “Burning” glucose in respiration. (Image bottom right copyright © 2002
from Molecular Biology of the Cell by Alberts et al. Reproduced by permission of
Garland Science/Taylor & Francis Books, Inc.)
oxidation of carbohydrate in the citric acid
cycle
(this
fragment
of is just a part) provides electrons
carbohydrate
two high-energy electrons
from oxidation of sugar
NAD+
H+ + 2e-
NAD+
NADH
NADHH
NAD+ stores energetic electrons
(with the help of a proton)
to electron
transport chain
NAD+
H+ + 2eH
hydride
ion
NADH
H
Slide 5: Key electron transport reactions within the citric acid cycle. (Images
adapted from Molecular Biology of the Cell by Alberts et al copyright © 2002.
Reproduced by permission of Garland Science/Taylor & Francis Books, Inc.)
-
10-7 M H+
1M NAD+
1M NADH
NAD+ + 2e- + H+
+
10-7M H+
1atm H2
NADH
Standard potential = –0.315 V: reaction proceeds in reverse
2e- + 2H+
H2
Standard potential = 0 V (by definition,
this is the reference reaction)
Slide 6: Measuring standard redox potentials. (Image copyright © 2002 from
Molecular Biology of the Cell by Alberts et al. Reproduced by permission of
Garland Science/Taylor & Francis Books, Inc.)
overall: 2e- + 2H+ + ½O2 → H2O
Slide 7: Electron transport chain – pumping protons. (Image copyright © 2002
from Molecular Biology of the Cell by Alberts et al. Reproduced by permission of
Garland Science/Taylor & Francis Books, Inc.)
protons move freely
through water by hopping
through the network of
hydrogen bonds
protons are readily donated to or
accepted from water – electron
transfer can be associated with the
formation and breakage of a
covalent bond to a hydrogen atom
transfer of electron through a
carrier can be coupled to the
pumping of a proton across the
membrane
Slide 8: Coupling proton pumping to electron transport. (Images copyright ©
2002 from Molecular Biology of the Cell by Alberts et al. Reproduced by
permission of Garland Science/Taylor & Francis Books, Inc.)
“food”
e.g. glucose
electrons
reproduction
photons
pmf
ATP
growth
transport
movement
FO
H+ or Na+
F1
ATP
ADP+ Pi
Slide 9: Structure and function of ATP synthase. (Left-hand image reproduced
from J.P. Abrahams et al. 1994 Nature 370 621–638 by permission from
Macmillan Publishers Ltd, © 1994.)
http://www.mrc-mbu.cam.ac.uk/category/slideshows/atpmovies
Slide 10: ATP synthase in action. (Movie © Medical Research Council,
reproduced by kind permission of John Walker.)
http://www.mrc-mbu.cam.ac.uk/category/slideshows/atpmovies
Slide 11: Catalytic cycle: ATP synthesis in F1. (Movie © Medical Research
Council, reproduced by kind permission of John Walker.)
Slide 12: Direct observation of rotation of F1 ATPase. (Image top-left from H Noji
et al. 1997 Nature 386 299–302, reproduced by permission of Macmillan, © 1997.
Movie bottom-left used by permission of Wolfgang Junge. Image right reproduced
from Yasuda, R et al. Cell 93 1117–1124 © 1998 by permission of Elsevier.)
Slide 13: Free energy accountancy: overall efficiency of conversion of glucose
into ATP.
“food”
e.g. glucose
electrons
reproduction
photons
pmf
ATP
growth
transport
movement
Slide 14: Light harvesting.
Membrane structure of chloroplast
Slide 15: Chloroplasts and mitochondria. (Left-hand image courtesy of K.
Plaskitt, both images from Alberts et al. Molecular Biology of the Cell,
reproduced by permission of Garland Science/Taylor & Francis Books, Inc. ©
2002.)
Slide 16: Electron transport and proton pumping in chloroplasts. (Image
copyright © 2002 from Molecular Biology of the Cell by Alberts et al. Reproduced
by permission of Garland Science/Taylor & Francis Books, Inc.)
Photosynthetic
Respiratory
Slide 17: Comparison between respiratory and photosynthetic electron
transport. (Left-hand image courtesy of K.N. Ferreira, both images from Alberts
et al. 2008 Molecular Biology of the Cell, reproduced by permission of Garland
Science/Taylor & Francis Books, Inc. © 2008.)