Something Cool

1
Something Cool

• CH339K

2
Wooly Mammoth Mammuthus primigenius

• Disappeared about 10,000 BC
• Frozen remains found periodically
• Wooly mammoth hemoglobin reconstructed
• Campbell, K.L. et al.(2010) Nature Genetics
  Advance Online Publication

3
Structure

• Asian elephant (left) and mammoth (right)
  deoxyhemoglobin with BPG (chimeric molecule)
• Blue location of mammoth mutations
• Yellow positive residues on b-chain

4

• Typical hemoglobin
• Increasing temperature shifts binding to right
• Blood entering warm, exercising muscles unloads
  more O2.

5
O2 Binding Curves Mammoth vs. Asian Elephant

• Intrinsic O2 affinity of mammoth Hb is 2 that of
  modern elephant
• In the presence of normal cofactors, the two are
  essentially identical
• Increased cofactor affinity, however, reduces
  temp effects on O2 binding
• Mammoth Hb spec\ialized to deliver O2 to tissues
  whether cold or hot
• Same adaptation seen in reindeer, musk oxen

6
Photosynthesis

• CH339K

7
6CO2 6 O2 ? C6H12O6

• Requires energy (big surprise)
• Provided by radiation
• 1017 kcal/year (1010 tons of carbohydrate
  produced - 2 tons/person)

8
(No Transcript)
9
(No Transcript)
10
Chloroplasts will reduce an artificial electron
acceptor when illuminated Hill Reaction
11
Where h 6.626 x 10-34 Jsec And n frequency
(NOT wavelength) For cyan-colored light, this
works out to 240 kJ/mol photons
12
Absorption of light

• Internal conversion - electronic energy converted
  to heat, time frame lt 10-11 s
• Fluorescence - excited state decays to ground
  state by emitting photon, time frame 10-8 s
• Exciton transfer (resonance energy transfer)
  excited molecule transfers its excitation energy
  to nearby unexcited molecules, important in
  funneling light energy to photosynthetic reaction
  centers
• Photooxidation - light-excited donor molecule
  transfers an electron to an acceptor molecule,
  the oxidized donor relaxes to ground state by
  oxidizing some other molecule

13
(No Transcript)
14
(No Transcript)
15
(No Transcript)
16
(No Transcript)
17
(No Transcript)
18
Chlorophyll is assembled in light harvesting
complexes Example shown contains Chlorophyll A
(green) Chlorophyll B (red) Lutein
(yellow) Chlorophylls and accessory pigments
harvest incoming photons and are excited Energy
is passed on through exciton transfer to a
reaction center
19
(No Transcript)
20
(No Transcript)
21
(No Transcript)
22
(No Transcript)
23
(No Transcript)
24
(No Transcript)
25
(No Transcript)
26
Need 2 e- to reduce the quinone
Pheo pheophytin Q quinone
27

• Rhodospirillum action center
• Excited chlorophyll passes electron to pheophytin
• Electron then passed to menaquinone
• Electron passed through Fe to ubiquinone QB
• Cytochrome donates electron back to action center
  chlorophyll

28
Green sulfur bacteria also have a non-cyclic
system that passes electrons through ferridoxin
to NADPH Ferridoxin is an iron-sulfur
protein Below is ferridoxin 1 from
Azotobacter Contains one 4Fe-4S cluster and one
3Fe-4S cluster
29
Energetics
30
Need 2 ferredoxins
Produces good reductant (Ch) and strong oxidant
(Z)
31
(No Transcript)
32
Organization of Photosystem 1
33
Cytochrome b6f Complex

• Proton pump
• Transfers electrons to Plastocyanin (carrier to
  PS1)
• As is complex 3 of ETC, electrons from QH2 have
  to cycle through one at a time

34
Ubiquinone
Plastoquinone
35
Cyclic Photophosphorylation

• To fix 1 CO2 requires
• 2 NADPH molecules
• 3 ATP molecules
• Each molecule of oxygen released by the light
  reactions supplies the 4 electrons needed to
  make 2 NADPH molecules.
• 4 electrons passingthrough cytochrome b6/f
  complex provides enough energy to pump 12
  protons into the interior of the thylakoid.
• To make 3 molecules of ATP, the ATPase in
  chloroplasts needs about 14 protons (H)
• Deficit is made up by cyclic photophosphorylation.
  
• Electrons expelled by the energy of light
  absorbed by photosystem I pass, as normal, to
  ferredoxin (Fd).
• Then pass to plastoquinone (PQ) and on back into
  the cytochrome b6/f complex.
• Here each electron liberates pumps 2 protons (H)
  into the interior of the thylakoid enough to
  make up the deficit left by noncyclic
  photophosphorylation.

36
(No Transcript)
37
Splitting Water
e- source for PS II
Complex associated with PS II uses several Mn
ions to extract 4 electrons from 2 water
molecules. P680 is rereduced by Tyrosine in the
PSII reaction center Tyrosine radical is
rerreduced by increasing oxidation state of a Mn
cluster When Mn cluster reaches 4 state, it can
grab 4 e- from 2 H2O