CHEM10006 Study Guide - Final Guide: Heme, Carbonic Anhydrase, Protein Precursor
12 Jun 2018
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Haemoglobin: carrier in blood, transport from lungs , changes
color with oxygen, deoxygenated blood is blue (veins)
●two alpha & two beta chains, beta chain is longer
●molecular weight: 64,500
●quaternary structure, 4 protein units each with a
haem group
Blue baby: deoxygenated blood: can indicate hypoxia
Myoglobin: storage in muscles/tissues
Bohr effect: Increased CO2 in the blood causes a drop in pH,
and decreases affinity of haemoglobin for O
2
allowing more O
2
to be released and respired
Haem group consists of an Fe(II) centre at the centre of a
porphyrin ligand: Flat, unsaturated, conjugated molecule which
upon deprotonation is able to bind a metal ion at its centre,
aromatic with many resonance forms, tetradentate ligand in
many biological systems containing metals
Haem group has two propanato groups attached to porphyrin
ring: bulky, negatively charged & hydrophilic
Haem group held to protein chain through histidine side chain
Coordination site on Fe(II) where O
2
coordinates is trans to
histidine group
Crowding of coordination site allows only small molecule to
access Fe(II) so anything other than O
2
cannot bind
O
2
binds but does not oxidize Fe
2+
Myoglobin has greater affinity for O
2
therefore converted to
oxymyoglobin even at low O
2
concentrations
Asphyxiation: Oxygen deprivation
Carbon monoxide: Has a stronger affinity for Fe(II) in
haemoglobin, displaces O
2
irreversibly, toxic/poisoning,
causes a steric clash with CO and surrounding protein chain
Training at altitude increases RBC count for extra O
2
carrying
capacity
Cu
+
& Cu
2+
very toxic when free: radicals that cause oxidative
stress
Within cells they are strongly bound to transport proteins or
enzymes
Cu
II
/Cu
I
couple: Cu
+
reduces O
2
catalytically by one electron to
create superoxide ions and H
2
O
2
to create hydroxyl radicals
(highly toxic)
Alzheimer's: Progressive mental deterioration, caused by a
copper transport protein precursor that degrades into small
pieces that precipitate into plaques of high metal content in
the brain
●Aspartic acid: Carboxylate side chain
Ferritin: Iron storage protein, rust coated with soluble protein
coat, large, 24 cylindrical subunits , cubic symmetry, hollow
sphere, can hold lots of iron, iron enters through channels at
corners of structure
Zinc complexes
Zn
2+
only oxidation state, filled valence shell, no strong
stereochemical preferences therefore can switch between
various coordination numbers (common: 4, 5, 6)
Readily available in natural waters
Catalyzes acid-base reactions
Exhibits no redox chemistry in nature
Preference for O & N donors
Allows HO
-
to act as a base in biological systems
Carbonic anhydrase: Speeds up reaction of CO
2
in water
(blood plasma) by a factor of 10
8
, a zinc (II) complex (protein)
with zinc acting as an OH
-
reagent; without a catalyst is too
slow, body would not be able to effectively respond to
increased CO
2
levels in the blood
Document Summary
Haemoglobin: carrier in blood, transport from lungs , changes color with oxygen, deoxygenated blood is blue (veins) Two alpha & two beta chains, beta chain is longer. Quaternary structure, 4 protein units each with a haem group. Bohr e(cid:710)ect: increased co2 in the blood causes a drop in ph, and decreases a nity of haemoglobin for o 2 allowing more o 2 to be released and respired. Carbon monoxide: has a stronger a nity for fe(ii) in haemoglobin, displaces o 2 irreversibly, toxic/poisoning, causes a steric clash with co and surrounding protein chain. Haem group has two propanato groups attached to porphyrin ring: bulky, negatively charged & hydrophilic. Haem group held to protein chain through histidine side chain. Coordination site on fe(ii) where o 2 coordinates is trans to histidine group. Crowding of coordination site allows only small molecule to access fe(ii) so anything other than o 2 cannot bind. O 2 binds but does not oxidize fe 2+
