7 nm Actin Filament Z-line 1) How many motor molecules matter? In muscle, myosin

Question

7 nm Actin Filament Z-line 1) How many motor molecules matter? In muscle, myosin motor molecules extend from the core of the thick filament binding to sites on actin monomers that comprise the thin filament. The myosin motors are spaced every 43 nm and the actin binding sites the face are spaced every 37 nm (4 pts) M-line 43 n Myosin Filament Titin (a) A myosin motor molecule must be within 2 nm of either side of a binding site to have a reasonable probability of binding. Under this condition, what fraction of myosin motors would actually bind? (show your work) (b) That distance of 2 nm is based on a motor molecule whose spring constant is 5 pN/nm. If the effective spring constant of the motor molecule were doubled, would the fraction of bound cross bridges increase or decrease? (explain your answer

Explanation / Answer

a. lets assume that at site 1, myosin molecule is perfectly aligned with the binding site
then distance of
site 2 from nearest myosin moleule = 43 - 37 = 6 nm
site 3 from nearest myosin moleule = 6 + 43 - 37 = 12 nm
site 4 from nearest myosin moleule = 12 + 43 - 37 = 18 nm
site 5 from nearest myosin moleule = 37 - (18 + 43 - 37) = 13 nm
site 6 from nearest myosin moleule = 37 - (24 + 6) = 7 nm
site 7 from nearest myosin moleule = 37 - (30 + 6) = 1 nm
site 8 from nearest myosin moleule = |37 - (36 + 6)| = 5 nm
site 9 from nearest myosin moleule = |37 - (42 + 6)| = 11 nm
site 10 from nearest myosin moleule = |37 - (48 + 6)| = 17 nm
site 11 from nearest myosin moleule = 37 - |37 - (52 + 6)| = 14 nm
site 12 from nearest myosin moleule = 37 - |37 - (58 + 6)| = 8 nm
site 13 from nearest myosin moleule = 37 - |37 - (64 + 6)| = 2 nm
14th site, 4 nm
15th site, 10 nm
16th site, 16 nm
17th site, 15 nm
18th site, 9 nm
19th site, 3 nm

hence every 37 sites, teh pattern is repeated
hence every 37 sites, number of myosin fibers present = 37*37/43 = 31
myosins attached = 5
hence 5*100/31 % = 16.12% of myosin fibers actually bind

b. if effective spring constant of myosin fibre is doubled, the distance of 2 nm will reduce to 1 nm, assuming a constant attractive force on the myosin fibre form the active site. This will reduce the % of binding myosins to 300/31 = 9.677 %

Related Questions

Navigate

• Browse (All)
• Browse 7
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.