[bu2012]

DNA can be treated as an elastic rod that can be twisted or bent. Suppose a DNA
molecule of length L is bent such that it lies on a circle of radius R. The reversible
work involved in bending the DNA is:
w_bend = BL/2R_c² where B is the bending force constant. 

DNA in a chromosome is found tightly wrapped around a protein core in a particle
called the nucleosome. The DNA in a nucleosomal particle is about 680
Angstroms (Å) in length. Nucleosomal DNA is bent around a protein complex
called the histone octamer into a circle of radius 55Å. Calculate the reversible
work involved in bending nucleosomal DNA around the histone octamer if the force constant is B = 2.00 * 10^-28 J m.

I found that w_bend is 2.25*10^-29 but I am unsure how w_reversible and w_bend are related? Any help is appreciated!

[jusy1]

Hi bu2012,

I don't know if this answers your question, but in any irreversible process there's always an increase of the entropy of the universe. That means that when you perform work on a system irreversibly, some of your work will be "wasted" as heat.
When your process is reversible you ensure that the work done will all be used to change your system's internal energy.
On your question it is stated that the equation is for reversible work, so w_reversible = w_bend.