Lecture 5 - Muscle Contraction - Sliding Filaments Flashcards
What does each myosin head have
An actin and myosin ATPase
What are the three major proteins of the thin filaments
Actin, tropomyosin and troponin
What structure do the actin molecules make
A helix
What does tropomyosin do
It covers the myosin binding sites on the actin molecules
What is troponin composed of
Three small spherical subunits
What do each of the subunits of troponin bind to
One binds to calcium, one binds to actin and one binds to tropomyosin
What is the function of troponin (calcium not present)
To stabilise the tropomyosin and ensure it is covering the myosin binding sites
What occurs to troponin when calcium appears within the cell
It undergoes a conformational change and causes the tropomyosin to be removed from the myosin binding site
What does the binding of the actin-myosin cross bridge trigger
The power stroke
Do the myosin heads work together or independantly
Independantly
What occurs to the thin filaments during contraction
The slide inwards over the stationary thick filaments
What do the thin filaments pull closer together
The Z lines
What shortens during contraction
Sarcomere
What areas within the muscle fibre shorten during contraction
The I band, H zone and distances between the Z lines
What areas of the muscle fibre remain constant during contraction
The A band
