Question

1- Describe two attributes that are different for hemoglobin and myoglobin; focus on characteristics that are a direct consequence of differences in tertiary and/or quaternary structure. For each attribute, be sure to specifically explain how 3° and 4° organization impacts the described differences.

2- The kinetics of an enzyme (E)-catalyzed reaction are measured over a range of substrate (S) concentrations in the presence or absence of a reversible inhibitor (I). The total enzyme concentration is 10 uM, and the inhibitor concentration used is 50 uM. Analysis of the data indicates that the enzyme operates with typical Michaelis-Menton kinetics. A double-reciprocal (Lineweaver-Burke) plot provides the following information:

y-intercept (absence of I) = 0.75 sec/uM
y-intercept (presence of I) = 2.5 sec/uM
slope (absence of I) = 3.5 sec
slope (presence of I) = 7.0 sec

(A) Calculate the V_max for this reaction in the absence of inhibitor.  Show all work & indicate proper units.

(B) Calculate the V_max for this reaction in the presence of inhibitor.  Show all work & indicate proper units.

Answer 1

Answer 1:

• Hemoglobin is the globular oxygen-transport protein of blood has a quaternary structure. It is a tetramer consists of four peptide subunits two alpha subunits and two beta subunits.
• Myoglobin is a heme protein. Myoglobin is a monomer consists of single polypeptide chain. It has a tertiary structure.
• Haemoglobin and myoglobin are differ in the binding affinities with oxygen.
• Haemoglobin supplies along with blood systemically all over the body while Myoglobin supplies and store oxygen to muscles only.

Hemoglobin	Myoglobin
Haemoglobin act as a carrier for carrying oxygen as well as carbon dioxide. It supplies haemoglobin along with blood systemically all over the body. As it is tetramer it binds four oxygen molecules. It binds oxygen loosely and with difficulty. Hemoglobin follows cooperative binding of oxygen. Hemoglobin shows a sigmoidal oxygen binding curve.	Myoglobin supplies and store oxygen to muscles only. Myoglobin binds one oxygen as it is monomer. Myoglobin has a strong affinity for binding for oxygen, which makes it able to store it effectively in muscles. It shows hyperbolic oxygen binding curve.