Question

Myoglobin has a Hill coefficient of 1.0 and hemoglobin has a Hill coefficient of \(2.8 .\) This indicates that A. an oxygen saturation curve for myoglobin would be sigmoidal. B. hemoglobin exhibits a simple equilibrium binding of oxygen. C. myoglobin shows negative cooperativity in its binding of oxygen. D. hemoglobin shows positive cooperativity in its binding of oxygen. E. only myoglobin would yicld a straight line in a Hill plot.

Short answer

A. An oxygen saturation curve for myoglobin would be sigmoidal. B. Hemoglobin exhibits a simple equilibrium binding of oxygen. C. Myoglobin shows negative cooperativity in its binding of oxygen. D. Hemoglobin shows positive cooperativity in its binding of oxygen. E. Only myoglobin would yield a straight line in a Hill plot. Answer: D. Hemoglobin shows positive cooperativity in its binding of oxygen.

Step-by-step solution

Understanding Hill Coefficient

Hill coefficient is a measure of cooperativity in biochemical reactions, such as the binding of oxygen to myoglobin and hemoglobin. A Hill coefficient greater than 1 indicates positive cooperativity (i.e., binding of one molecule enhances the binding of successive molecules), while a Hill coefficient of exactly 1 suggests no cooperativity or simple equilibrium binding.

Interpreting Hill coefficients of myoglobin and hemoglobin

The Hill coefficient of myoglobin is 1.0, which indicates that there's no cooperativity in myoglobin's binding of oxygen (i.e., it follows simple equilibrium binding). On the other hand, hemoglobin's Hill coefficient is 2.8, which is greater than 1, suggesting positive cooperativity in its binding of oxygen.

Evaluating the given statements based on Hill coefficients

A. An oxygen saturation curve for myoglobin would be sigmoidal. This statement is incorrect, as myoglobin binding of oxygen follows a simple equilibrium (Hill coefficient of 1) and has a hyperbolic curve, not a sigmoidal curve. B. Hemoglobin exhibits a simple equilibrium binding of oxygen. This statement is incorrect, as hemoglobin shows positive cooperativity in its binding of oxygen (Hill coefficient of 2.8), indicating that it doesn't follow simple equilibrium binding. C. Myoglobin shows negative cooperativity in its binding of oxygen. This statement is incorrect because myoglobin's Hill coefficient of 1.0 suggests no cooperativity or simple equilibrium binding. D. Hemoglobin shows positive cooperativity in its binding of oxygen. This statement is correct, as hemoglobin's Hill coefficient of 2.8 is greater than 1, indicating positive cooperativity in its binding of oxygen. E. Only myoglobin would yield a straight line in a Hill plot. This statement is incorrect, as Hill plots for both proteins wouldn't produce a straight line due to their cooperative binding of oxygen. Based on our analysis, the correct answer is #(D)#, as hemoglobin shows positive cooperativity in its binding of oxygen.