Flashcards
Hb
Cards in this deck (14)
- 1human Hb is a tetrameric proton of Mr? it has 4 subunits each contain a ___? an adult Hb (HbA) has what chains?Mr 64400
each contain a harm group with its Fe''
has 2 identical a-chians and 2 identical b-chains, and packed in a tetrahedral array - 2the a and b chains of Hb closely resemble Mb, but Mb carries ? versus Hb?Mb carries charged Aa's at positions which are hydrophobic in Hb and which are important in binding the HB subunits together
- 3tetramer = a2b2 a chains has __ aa? beta chains have ___ aa? Hb in urea dissolves into ?a chains have 141 aa's
b chains have 146 aa's
Hb in urea dissolves 2 ab dimers
the dimers = a1b1 and a2b2 = 2 stable units - 4what is the level contact between a chains b chinas and the dimers?little contact between the a-chains
no contact between the b cahins
and strong contacts between the a1b1 dimer and a2b2 dimer - 5allostery Hb transports____ and ___ as well as O2 what are the 3 allosteric molecules?Hb transports H+ and CO2 as well as O2
regulated by H+, Co2, and 2,3-BPG
they regulate despite binding to sites distant from the haem
= allosteric interactions - 6Mb-O2 binding curve is a hyperbolic shape = simple binding interaction, no cooperative but Hb-O2 binding is cooperative, what shape of curve?shows a sigmoidal shape, means positively cooperative = binding of O2 at one hame enhances the binding of O2 to the other haems
- this makes Hb a more efficient transporter - 7what is the P50 of HB in RBCS? versus MB?P50 (partial pressure at which sites are half-filled) = 26.6 mmHg in RBCs
Mb with p50 = 2.75 mmHg (an order of magnitude more tightly than Hb) - 8pure Hb in the absence of significant quantities of regulators, would be?binds o2 too tightly for physiological need, for pure Hb, p50 = 2-5 mmHg similar to Mb
the regulators each weaken O2 affinity to enable Hb to unload oxygen better - 9the effects of H+ is called the ___ affect? what happens?Bohr effect
in exercising muscles lactic acid is formed and acidification of venous blood from the dissolution of CO2 and its subsequent ionizations, so H+ concentration rises
oxygen dissociation curve shifts to the right and more O2 is released. increased acidity enables the delivery of more O2 without a fall of O2 tension - 10effect of CO2 CO2 produced by aerobic metabolism is mostly transported as bicarbonate, but i can alsoCO2 also reacts with the N=terminal a-amino groups to form carbamates
and the carbamates form electrostatic bonds
(both being transported and act as allosteric regulators) - 11how is 2,3-BPG formed and what it binds to? what it does to the curve?its produced in RBCS from glycolysis in concentration of 4-5 mM (same as HB)
binds only to deoxyhaemoglobin with one molecule of BPG between the 2 beta-subunits of Hb
it shifts the dissociation curve to the right, weakening O2 affinity
*BPG - importance b/c if absent HB would unload little O2 in passing through the tissue capillaries - 12what is the PO2 is tissue capillaries?PO2 in tissue capillaries is about 26 mmHg , therefore hard to unload and needs BPG
- 13foetal Hb has ___ and is __ on the curve?has higher affinity for O2,
normal adult Hb is further on the right on the curve
so foetal Hb curve to the left - 14increased temperature also causes the curve to shift to the right, increasing the release of O2, active muscle for examplesummary:
HB
composed of 4 subunits similar in structure to Mb
binds 4 O2 molecules in a positively co-operative manner
o2 binding is affected by tempt, H+, Co2, 2,3-BPG
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- biological sciences Biol 115 Flashcards on Hb, created by Jenny Lee7018 on 15/05/2016.
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- Jenny Lee7018
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