1.Starting from the O2 binding equilibrium of human hemoglobin written below, derive theHbnO22 Hb(O2)n+equation underlying the Hill plot. Draw a generic Hill plot and indicate at what O2 saturation conditionsthe equilibrium dissociation constants (Kd, K1, K4) are defined by the plot. Also, show how the valuesof the Hill coefficient are determined at 50% saturation and at their asymptotic limits. Explain theinterpretation of the value of the Hill coefficient nH at 50% saturation compared to the total number ofsubunits in the allosteric molecule.

Fractional saturation 'Y' can be written as; Y= [L]n[L]n + Kd ' here 'L' is O2 .…

Answered: Starting from the O2 binding…

Biochemistry

9th Edition

ISBN:9781319114671

Author:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.

Publisher:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.

Chapter1: Biochemistry: An Evolving Science

Section: Chapter Questions

Problem 1P

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What qualitative effect would you expect each of the following to have on the Ps0 of hemoglobin? (a) Increase in pH from 7.2 to 7.4 (b) Increase in Pco, from 20 to 40 mm Hg (c) Dissociation into monomer polypeptide chains
Studies of oxygen transport in pregnant mammals show that the O2-saturation curves of fetal and maternal blood are markedly different when measured under the same conditions. Fetal erythrocytes contain astructural variant of hemoglobin, HbF, consisting of two α and two γ subunits (α2 γ2 ), whereas maternal erythrocytes contain HbA (α2β2).(a) Which hemoglobin has a higher affinity for oxygen under physiological conditions, HbA or HbF? Explain.(b) What is the physiological significance of the different O2 affinities?(c) When all the BPG is carefully removed from samples of HbA and HbF, the measured O2 -saturation curves (and consequently the O2 affinities) are displaced to the left. However, HbA now has a greater affinity for oxygen than does HbF. When BPG is reintroduced, the O2 -saturation curves return to normal, as shown in the graph. What is the effect of BPG on the O2 affinity of hemoglobin? How can the above information be used to explain the different O2 affinities of fetal and…
Heterozygotes for erythropoietic protoporphyria show only 20 to 30% residual ferrochelatase activity rather than the 50% that is normally expected for an autosomal dominant inherited disease. Provide a plausible explanation for this observation.
The hexapeptide Ala-Met-Leu-Lys-Phe-Asp is digested in the same tube with both Cyanogen Bromide and Trypsin at the same time at pH=7. Draw the structure of the product(s) that would bind to a cation exchange column. (Relevant pKa values are 2.2, 3.9, 9.5 and 10.5. Assume pKa values for any newly generated a-amino and a-carboxyl groups are 9.5 and 2.2 respectively)
The O2-consumption curve of a dilute, well-buff ered suspension of mito chondria containing an excess of ADP and Pi takes the following form: Sketch the curves obtained when (a) amytal is added at time t = 1 and (b) amytal is added at t = 1 and succinate is added at t = 2.
In active muscle cells, the pO₂ is about 10 torr at the cell surface and 1 torr at the mitochondria (the organelles where oxidative metabolism occurs). Calculate the percentage of bound oxygen transported to the mitochondria of muscle cells by myoglobin (KD = 2 torr). A new oxygen transport protein that exhibits cooperative binding has been isolated and is being studied in the lab. Calculate the Ko value if Y = 0.76 when pO₂2 = 18 torr (assume n = 2.5). How does this compare to the K₂ value for hemoglobin? Does this protein bind more or less tightly to oxygen compared to hemoglobin?
Amino acid substitutions at the interfaces of the a and B subunits of hemoglobin can change the relative stability of the oxy (R) and deoxy (T) forms of the molecule. In one mutant hemoglobin molecule a hydrogen bond involved in stabilizing the R form of the molecule is lost. As a result, would expect this mutant hemoglobin to have a higher or lower affinity for oxygen as a ligand. Explain.
1.12 At elevated altitudes, the body adapts to the reduced barometric pressure to extract sufficient oxy- gen to permit normal metabolic functions and do work. For example, at an altitude of 3,650 m (close to 12,000 feet above sea level) the barometric pressure drops to 485 mmHg. For an oxygen pressure drop in the lungs of 30 mmHg, determine the oxygen uptake rate for a respiration rate of 20 breaths per minute. Estimate the oxygen saturation in venous blood if the hematocrit rises to 0.60 and the partial pressure of oxygen blood is at a partial pressure equal to 98% of the alveolar level.
In active muscle cells, the pO2 is about 10 torr at the cell surface and 1 torr at the mitochondria(the organelles where oxidative metabolism occurs). Calculate the percentage of bound oxygentransported to the mitochondria of muscle cells by myoglobin (KD = 2 torr).
On the right the Hill plot com- (b) pares the O2 binding properties of Hb Ya- kima with those of HbA in 0.1 M NaCl buff- Hb-Yakima ered to pH 7 with 0.01 M bis-Tris. Focus first on the line for "stripped Hb". This is the term for hemoglobin isolated from erythro- cytes with removal of all organic phosphate molecules that might bind to the protein in RBCS. You can see that 2,3-bisphospho- glycerate (BPG; labeled DPG according to old terminology) does not alter the O2 bind- ing affinity of Hb Yakima in contrast to HbA (although it was shown that BPG did bind to the deoxyHb Yakima molecule). Also, Hb Yakima is associated with markedly decreased allostery in the absence and presence of BPG, in comparison to HbA. IHP = inositol hexaphosphate, an artificial allosteric modifying ligand that binds more tightly than BPG. stripped Hb Hb-A •DPG +DPG n= 1.0 n = 2.3 n=2,5 +THP +IHP 0.5 0.5 1 5 10 50 po, ( mm Hg ) %3D On the right is a diagram copied from the lecture handout "Hemoglobin and Allo-…
The figure shows three oxygen binding curves for hemoglobin in the red blood cells of normal blood, pH 7.6. The middle-dashed line is the standard line for human hemoglobin. Lines A and B represent two experimental conditions your lab partner plotted but forgot to label. 1 0.8 0.6 0.4 0.2 | pO2 Q. which one is the hemoglobin you reduced the concentration of 2,3- bisphosphoglycerate in? and which line is the data from the hemoglobin you changed the pH to 7.3?
13. 0.9% (m/v) NaCI solution and 5% (m/v) glucose solution are both isotonic to red blood cells. SHOW your work and watch sig figs & units. c. convert the concentration from M to % (m/v) for a 0.342 M NaC solution. (HINT: convert to g/ml and then multiple by 100%)

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