The substation of valine for glutamic acid in the sixth position of the beta-cha

Question

The substation of valine for glutamic acid in the sixth position of the beta-chain of hemoglobin produces sickle-cell anemia in the homozygote because (a) Co-operative binding of oxygen is lost because of the missing Glu-6 residue. As such the cell prevents oxygen from reaching the spleen, liver, kidneys, lungs, heart, or other organs, causing a lot of damage. (b) The Apoprotein can no longer protect the heme iron from becoming oxidized owing to the presence of the hydrophobic Val-6 (c) The Val-6 variant loses solubility upon deoxygenation (d) The Val-6 variant tends to retain oxygen when the oxygen tension is low (e) The red cell is unable to sequester high enough concentrations of the Val-6 variant hemoglobin The lock and key theory of enzyme activity is where (a) The site other than the active site of the enzyme is non-complimentary in conformation to the substrate (b) The active site of the enzyme is non-complimentary in conformation to the substrate (c) The site other than the active site of the enzyme is complimentary in conformation to the substrate (d) The active site of the enzyme is complimentary in conformation to the substrate (e) None of the above. The induced theory of enzyme activity is where the enzyme changes shape upon binding the substrate so that (a) The conformation of substrate and enzyme protein are only non complimentary after the binding reaction (b) The conformation of substrate and enzyme protein are only associative after the binding reaction (c) The conformation of substrate protein are only complimentary after the binding reaction (d)

Explanation / Answer

24. D) the active site of the enzyme is complimentary in conformation to the substrate.

The lock and key analogy was given by Emil Fischer in which lock is similar to the enzyme and key resembles the substrate where the substrate only fits onto an enzyme whose active site has the correct conformation as that of the substrate.

25. C) the conformation of substrate and enzyme protein are only complimentary after the binding reaction

The induced fit theory states that when the substrate binds to the enzyme, it induces a change in the shape of the enzyme such that it would enhance or inhibit the activity of the enzyme.

23. A) co-operative binding of oxygen is lost because of the missing Glu-6 residue . As such the cell prevents oxygen from reaching the spleen, liver, kidneys, lungs heart or other organs, causing a lot of damage.

Sickle cell anemia , which is caused by valine substituted for glutamic acid. There is a reduction in oxygen carrying capability.

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