2
String Filament Theory steps (ordered):
–Calcium ions are released by sarcoplasmic reticulum into the sarcoplasm.
–The breakdown of ATP releases energy, releasing the head of the myosin.
–Calcium ions bind to troponin, exposing the binding site on the actin filament.
–The myosin head attaches to the exposed binding site on the actin filament, forming a cross-bridge.
–The flexing of the cross-bridge pulls the actin filament toward the center of the sarcomere.
–An ATP molecule in the reattaches to the ATP binding site on the myosin head.
–The myosin head is released from the actin filament’s binding site and the binding site is covered up again.
–With the ATP molecule in place on the myosin head and calcium ions present, the cycle can continue.
The cells of our skeletal muscles are made up of complex proteins called myofibrils. These myofibrils are further divided into sections called sarcomeres. All of the exciting chemistry that creates muscle movement occurs here in the sarcomere. Each muscle has thousands of these sections, and they all contract together to produce movement. To understand what happens within each sarcomere, it is necessary to look a little more closely. Within each sarcomere, there are layers of protein strands called myofilaments. There are two types of myofilaments, actin and myosin.--Myosin strands have golf-club shaped objects called “heads” attached to them. They are located at the center of a sarcomere.Actin strands are thinner proteins and surround the thicker myosin strand in the sarcomere. The actual number of actin strands encircling myosin depends upon the specific muscle. Larger muscles would have more, and smaller muscles would have fewer
AEROBIC RESPIRATION-Cells only store a small amount of ATP molecules, so the chemical process of cellular respiration is necessary to convert energy from our food into enough energy for ongoing muscle contraction and other cellular work. The organic molecules in food contain stored energy
–Calcium ions are released by sarcoplasmic reticulum into the sarcoplasm.
–The breakdown of ATP releases energy, releasing the head of the myosin.
–Calcium ions bind to troponin, exposing the binding site on the actin filament.
–The myosin head attaches to the exposed binding site on the actin filament, forming a cross-bridge.
–The flexing of the cross-bridge pulls the actin filament toward the center of the sarcomere.
–An ATP molecule in the reattaches to the ATP binding site on the myosin head.
–The myosin head is released from the actin filament’s binding site and the binding site is covered up again.
–With the ATP molecule in place on the myosin head and calcium ions present, the cycle can continue.
The cells of our skeletal muscles are made up of complex proteins called myofibrils. These myofibrils are further divided into sections called sarcomeres. All of the exciting chemistry that creates muscle movement occurs here in the sarcomere. Each muscle has thousands of these sections, and they all contract together to produce movement. To understand what happens within each sarcomere, it is necessary to look a little more closely. Within each sarcomere, there are layers of protein strands called myofilaments. There are two types of myofilaments, actin and myosin.--Myosin strands have golf-club shaped objects called “heads” attached to them. They are located at the center of a sarcomere.Actin strands are thinner proteins and surround the thicker myosin strand in the sarcomere. The actual number of actin strands encircling myosin depends upon the specific muscle. Larger muscles would have more, and smaller muscles would have fewer
AEROBIC RESPIRATION-Cells only store a small amount of ATP molecules, so the chemical process of cellular respiration is necessary to convert energy from our food into enough energy for ongoing muscle contraction and other cellular work. The organic molecules in food contain stored energy