Answer:
A protein has four subunits whose molecular masses are 140, 80, and 60 kDa.
A disulfide bond links the two 80 kDa subunits (possibly identical).
Explanation:
Given that:
A protein has four subunits whose molecular masses are 140, 80, and 60 kDa.
A disulfide bond links the two 80 kDa subunits (possibly identical).
As a result of SDS and dithiothreitol analysis treatment, the molecular masses can not be 360 in total. They are 280, which implies that they are in short of 80 kDa. This means that there are possibilities that two groups with a molecular mass of 80 kDa which are joined by a disulfide bond.
The presence of SDS and dithiothreitol acts as a reducing agent, and they can break disulfide bonds whose pH is greater than 7, i.e. those in basic condition.
Answer:
∆H° rxn = - 93 kJ
Explanation:
Recall that a change in standard in enthalpy, ∆H°, can be calculated from the inventory of the energies, H, of the bonds broken minus bonds formed (H according to Hess Law.
We need to find in an appropiate reference table the bond energies for all the species in the reactions and then compute the result.
N₂ (g) + 3H₂ (g) ⇒ 2NH₃ (g)
1 N≡N = 1(945 kJ/mol) 3 H-H = 3 (432 kJ/mol) 6 N-H = 6 ( 389 kJ/mol)
∆H° rxn = ∑ H bonds broken - ∑ H bonds formed
∆H° rxn = [ 1(945 kJ) + 3 (432 kJ) ] - [ 6 (389 k J]
∆H° rxn = 2,241 kJ -2334 kJ = -93 kJ
be careful when reading values from the reference table since you will find listed N-N bond energy (single bond), but we have instead a triple bond, N≡N, we have to use this one .
Answer: the answer is number 3 which is 6
