25.) (3 pts) Hb Rainier, 145(HC2) β Tyr → Cys. The mutant cysteine forms a disulfide bond with another cysteine of the β-subunit that stabilizes the R-state. How would this mutation affect the oxygen affinity? (A) increase (B) decrease (C) remain the same (D) cannot be determined. 26.) (3 pts) Hb Rainier, 145(HC2) β Tyr → Cys. The mutant cysteine forms a disulfide bond with another cysteine of the β-subunit that stabilizes the R-state. How would this mutation affect the hill coefficient of Hb Rainier? (A) increase (B) decrease (C) remain the same (D) cannot be determined. 27.) (3 pts) What is the role of His-146 of the β-subunits? 28.) (3 pts) Hb Cowtown, 146(HC3) β His → Leu. What is the role of His-146 of the β-subunits? How would this mutation affect the oxygen affinity of Hb Cowtown? (A) increase (B) decrease (C) remain the same (D) cannot be determined. 29.) (2 pts) A monomeric oxygen-binding protein has a fractional saturation of 0.85 when pO2 = 7.3 torr. What is the value of the hill coefficient n? 30.) (3 pts) A monomeric oxygen-binding protein has a fractional saturation of 0.85 when pO2 = 7.3 torr. What is the value of p50 for this protein? 31.) (2 pts) A monomeric oxygen-binding protein has a fractional saturation of 0.35 when pO2 = 15.8 torr. What is the value of the hill coefficient n? 32.) (3 pts) A monomeric oxygen-binding protein has a fractional saturation of 0.35 when pO2 = 15.8 torr. What is the value of p50 for this protein? 33.) (3 pts) Calculate the fractional saturation of hemoglobin at a pO2 = 15 torr. The Hill coefficient of Hb is 3.0 and using a p50 = 27 torr. 34.) (3 pts) Calculate the fractional saturation of hemoglobin at a pO2 = 15 torr. The Hill coefficient of Hb is 3.0 and using a p50 = 0.30 torr.
Added by Henry H.
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This would lead to an increase in oxygen affinity. Step 2: The mutation in Hb Rainier, 145(HC2) β Tyr → Cys would not directly affect the hill coefficient of Hb Rainier. Step 3: The role of His-146 of the β-subunits is to interact with the heme group and help in Show more…
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35) A red protein isolated from erythrocytes would most likely be which of the following? (a) hemoglobin (b) myoglobin (c) Immunoglobulin A (d) collagen (e) alpha amylase 36) Which of the following types of bonds or interactions is involved in holding subunits of an oligomeric protein together? (a) electrostatic interactions (b) hydrophobic interactions (c) disulfide bonds (d) all of the above 37) Hemoglobin contains a significant proportion of alpha helix structure. (a) true (b) false 38) At its isoelectric point, an immunoglobulin G molecule has: (a) No net charge (b) An overall negative charge (c) An overall positive charge (d) all of the above 39) Which of the following amino acids in a protein contains a side chain that may be covalently modified with a phosphate group? (a) lysine (b) alanine (c) tryptophan (d) tyrosine 40) In the formation of a peptide bond, which of the following is lost? (a) CO2 (b) CH3 (c) H2O (d) H2O2 41) Two different proteins can have the same amino acid composition. (a) true (b) false 42) Proteins have an alpha carboxyl group at their beginning. (a) true (b) false 43) Two different proteins can have the same amino acid sequence. (a) true (b) false 44) Which of the following is not an amino acid that is found in proteins? (a) glutamic acid (b) aspartic acid (c) glutamine (d) palmitic acid (e) leucine 45) Immunoglobulin G does not have quaternary structure. (a) true (b) false 46) Immunoglobulin G is composed of identical subunits. (a) true (b) false 47) The variable domain of IgA is found at: (a) the N-terminus (b) the C terminus (c) the hinge region (d) the Fab domain (e) none of the above 48) Five proteins, all the same molecular weight but having different pI values, are separated by electrophoresis at pH 9. Which of the proteins below will migrate furthest toward the positive electrode, the one with? (a) pI = 10.0 (b) pI = 7.0 (c) pI = 11 (d) pI = 9 (e) pI = 8 49) Which of the following amino acids in a protein contains a side chain that may be covalently modified with a phosphate group or alternatively with carbohydrate? (a) lysine (b) alanine (c) tryptophan (d) threonine
Adi S.
2,3-Bisphosphoglycerate (2,3-BPG) is an allosteric modifier that binds to the central cavity of hemoglobin. 2,3-BPG affects hemoglobin's affinity for oxygen by binding at a site different than the oxygen binding site and promoting shape change in the molecule. The result of 2,3-BPG binding is that oxygen binding curves shift right. When the small molecule is the same as the normal ligand for the protein, this interaction is called homotropic, as it is for oxygen and hemoglobin. The interaction of 2,3-BPG with hemoglobin is heterotropic since BPG and oxygen are not the same and do not bind to the same site. Define 2,3-BPG, cooperativity, oxygen affinity, and allosterism. How do all of these terms relate? The molecule 2,3-BPG binds to the deoxy form of hemoglobin in the central cavity. Explain why that makes sense for oxygen delivery and why BPG is said to stabilize the deoxy state. How do the levels of O2 in the atmosphere compare at sea level versus high altitude? Predict the blood levels of BPG for people who live at high altitudes, like Denver. How will those levels of BPG help their hemoglobin function better? In the mutant hemoglobin known as Hb Providence, an asparagine residue in the B-chain replaces Lys82. In normal hemoglobin, Lys82 projects into the central cavity of the hemoglobin molecule. Predict the effect of the Lys Asn mutation on the affinity of allosteric modifiers (relative to normal Hb, e.g., Hba) and describe the effect the mutation would have on the function (oxygen binding) of Hb Providence. Under appropriate conditions, hemoglobin dissociates into its four subunits. Isolated subunits bind oxygen, but the O2 saturation curve is hyperbolic instead of sigmoidal. In addition, the saturation curve is not affected by the presence of H, CO, or 2,3-BPG. What do these observations indicate about the cooperativity and allosterism observed in hemoglobin?
Dominador T.
A three-point testcross was made in corn. The results and a recombination analysis are shown in the display below, which is typical of three-point testcrosses $(p=$ purple leaves, $+=$ green; $v=$ virus-resistant seedlings, $+$ $=$ sensitive; $b=$ brown midriff to seed, $+=$ plain ). Study the display, and answer parts $a$ through $c$ $$\begin{aligned}&P \quad+/+\cdot+/+\cdot+/+\times p / p \cdot v / v \cdot b / b\\&\text { Gametes } \quad+\cdot+\cdot+\quad p \cdot v \cdot b\end{aligned}$$ a. Determine which genes are linked. b. Draw a map that shows distances in map units. c. Calculate interference, if appropriate. 1. Sketch cartoon drawings of the $\mathrm{P}, \mathrm{F}_{1},$ and tester corn plants, and use arrows to show exactly how you would perform this experiment. Show where seeds are obtained. 2. Why do all the $+$ 's look the same, even for different genes? Why does this not cause confusion? 3. How can a phenotype be purple and brown, for example, at the same time? 4. Is it significant that the genes are written in the order $p-v-b$ in the problem? 5. What is a tester and why is it used in this analysis? 6. What does the column marked "Progeny phenotypes" represent? In class $1,$ for example, state exactly what "gre sen pla" means. 7. What does the line marked "Gametes" represent, and how is it different from the column marked "F $_{1}$ gametes"? In what way is comparison of these two types of gametes relevant to recombination? 8. Which meiosis is the main focus of study? Label it on your drawing. 9. Why are the gametes from the tester not shown? 10. Why are there only eight phenotypic classes? Are there any classes missing? 11. What classes (and in what proportions) would be expected if all the genes are on separate chromosomes? 12. To what do the four pairs of class sizes (very big, two intermediates, very small) correspond? 13. What can you tell about gene order simply by inspecting the phenotypic classes and their frequencies? 14. What will be the expected phenotypic class distribution if only two genes are linked? 15. What does the word "point" refer to in a three-point testcross? Does this word usage imply linkage? What would a four-point testcross be like? 16. What is the definition of recombinant, and how is it applied here? 17. What do the "Recombinant for" columns mean? 18. Why are there only three "Recombinant for" columns? 19. What do the R's mean, and how are they determined? 20. What do the column totals signify? How are they used? 21. What is the diagnostic test for linkage? 22. What is a map unit? Is it the same as a centimorgan? 23. In a three-point testcross such as this one, why aren't the $\mathrm{F}_{1}$ and the tester considered to be parental in calculating recombination? (They are parents in one sense.) 24. What is the formula for interference? How are the "expected" frequencies calculated in the coefficient-ofcoincidence formula? 25. Why does part $c$ of the problem say "if appropriate"? 26. How much work is it to obtain such a large progeny size in corn? Which of the three genes would take the most work to score? Approximately how many progeny are represented by one corncob?
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