Which statement is correct regarding thick filament structure?
All the myosin molecules are arranged with their tails pointing away from the M line.
The free myosin head has three globular protein subunits.
It consists of a core of titin, forming a strand that continues across the I band to the Z line on that side.
Each long myosin tail is bound to actin molecules within the thick filament.
I have read my notes, and it seems as if all of these statements in some way are wrong.
It consists of a core of titin, forming a strand that continues across the I band to the Z line on that side
It consists of a core of titin, forming a strand that continues across the I band to the Z line on that side.
It seems like none of the given statements accurately describe the structure of thick filaments. Let's break down each statement and explain why they are incorrect:
1. "All the myosin molecules are arranged with their tails pointing away from the M line."
This statement is incorrect. In the sarcomere, the basic unit of a muscle, thick filaments composed of myosin molecules are arranged with their tails pointing towards the M line, which is located in the middle of the sarcomere.
2. "The free myosin head has three globular protein subunits."
This statement is also incorrect. The myosin head has two globular protein subunits, not three. These subunits contain the actin-binding site and the ATP-binding site, which are essential for muscle contraction.
3. "It consists of a core of titin, forming a strand that continues across the I band to the Z line on that side."
This statement is not accurate either. While titin is indeed a protein found in muscle cells, it does not form the core of the thick filament. Instead, titin is a structural protein that functions as a molecular spring, providing elasticity to the muscle. The thick filament primarily consists of myosin molecules.
4. "Each long myosin tail is bound to actin molecules within the thick filament."
This statement is incorrect as well. The myosin tails are not directly bound to actin molecules within the thick filament. Instead, the myosin heads interact with actin molecules from the thin filament to form cross-bridges during the muscle contraction process.
In summary, none of the given statements accurately describe the structure of thick filaments. It is always important to critically evaluate the information presented and cross-reference with reliable sources to ensure accuracy.