CHAPTER 9 HEMOGLOBIN AND MYOGLOBIN 1. Which of these statements is correct? Hemo
ID: 270221 • Letter: C
Question
CHAPTER 9 HEMOGLOBIN AND MYOGLOBIN 1. Which of these statements is correct? Hemoglobin is tetrameric, myoglobin is monomeric b hemoglobin is monomeric; myoglobin is tetrameric c) hemoglobin is tetrameric myoglobin is dimeric d) both hemoglobin and myoglobin are dimeridc 2. Which of these statements is correct? a) hemoglobin shows cooperative axygen binding b) myoglobin shows cooperative oxygen binding c) hemoglobin contains iron while myoglobin does not d) The beta subunit of hemoglobin is made up of beta sheets 3. group b) the proximal His c) the distal His d) the central cavity (BPG) binds to which part of the hemoglobin molecule? a) the heme 4. A person with sickle cell trait has: a) 50% hemoglobin-S and 50% sickled cells b) 50% hemoglobin-S and 1% sickled cells c) 1% hemoglobin-S and S0% sickled cells d) 1% hemoglobin-S and 1% sickled cellsExplanation / Answer
1. Hemoglobin transports molecular oxygen to tissues by binding to oxygen on RBCs in blood. Myoglobin on the other hand binds to molecular oxygen and transports it to muscle tissue. Hemoglobin is a tetrameric protein while myoglobin is a monomeric protein. So, the correct option is option A, hemoglobin is tetrameric; myoglobin is monomeric.
2. Myoglobin binds to oxygen easily and more tightly. However, hemoglobin has a low affinity for oxygen in its deoxygenated state. It binds to oxygen loosely and with difficulty. Binding of oxygen to the first subunit of hemoglobin causes a subtle conformational change in its quaternary structure which makes it easier subsequent binding of oxygen molecule to the next subunit. The initial binding of an oxygen molecule to a hemoglobin subunit makes the other subunits more receptive to oxygen. This phenomenon is known as allosteric interaction or cooperative binding. Therefore, hemoglobin shows cooperative oxygen binding. So, the correct option is option A, hemoglobin shows cooperative oxygen binding.
3. Bisphosphoglycertae is present on RBCs. It has a higher affinity for deoxygenated hemoglobin compared to oxygenated hemoglobin. It binds to the central cavity of the hemoglobin molecule, thereby decreasing the hemoglobin subunits affinity for oxygen. Binding of Bisphosphoglycerate to hemoglobin molecule enhances the ability of RBCs to release oxygen near tissues. So, the correct option is option D, the central cavity.
4. Sickle cell trait is a condition in which the person is heterozygous for sickle cell allele. A person with sickle cell trait carries one normal hemoglobin beta allele and another abnormal allele for hemoglobin beta gene known as the sickle cell allele. A person with sickle cell trait will exhibit co-dominance with respect to hemoglobin concentration in circulation which means the individual will have 50% hemoglobin S and 50% hemoglobin A. With respect to shape of RBC, a person with sickle cell trait will exhibit incomplete dominance which means sickle shaped RBC are found only at low oxygen concentrations (1%). So, the correct option is option B, 50% hemoglobin-S and 1% sickled cells.