Myofilament
Encyclopedia
Myofilaments, the filament
s of myofibrils constructed from protein
s,. The principal types of muscle are striated muscle, obliquely striated muscle and smooth muscle. Various arrangements of myofilaments create different muscles. Striated muscle
has transverse bands of filaments. In obliquely striated muscle, the filaments are staggered,and smooth muscle has irregular arrangements of filaments.
There are three different types of myofilaments: thick, thin, and elastic filaments.
The protein complex composed of actin and myosin, contractile proteins, is sometimes referred to as "actomyosin". In striated muscle
, such as skeletal
and cardiac muscle
, the actin and myosin filaments each have a specific and constant length in the order of a few micrometers, far less than the length of the elongated muscle cell
(a few millimeters in the case of human skeletal muscle
cells). The filaments are organized into repdeated subunits along the length of the myofibril. These subunits are called sarcomere
s.
Protein filament
In biology, a filament is a "long chain of proteins, such as those found in hair, muscle, or in flagella". They are often bundled together for strength and rigidity. Some cellular examples include:*Actin filaments*Microtubules*Intermediate filaments...
s of myofibrils constructed from protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
s,. The principal types of muscle are striated muscle, obliquely striated muscle and smooth muscle. Various arrangements of myofilaments create different muscles. Striated muscle
Striated muscle
Striated muscle tissue is a form of fibers that are combined into parallel fibers. More specifically, it can refer to:* Cardiac muscle .* Skeletal muscle* Branchiomeric muscles...
has transverse bands of filaments. In obliquely striated muscle, the filaments are staggered,and smooth muscle has irregular arrangements of filaments.
There are three different types of myofilaments: thick, thin, and elastic filaments.
- Thick filaments consist primarily of the protein myosinMyosinMyosins comprise a family of ATP-dependent motor proteins and are best known for their role in muscle contraction and their involvement in a wide range of other eukaryotic motility processes. They are responsible for actin-based motility. The term was originally used to describe a group of similar...
. Each thick filament are approximately 15 nm in diameter, and each is made of several hundred molecules of myosinMyosinMyosins comprise a family of ATP-dependent motor proteins and are best known for their role in muscle contraction and their involvement in a wide range of other eukaryotic motility processes. They are responsible for actin-based motility. The term was originally used to describe a group of similar...
. - Thin filaments, 7 nm in diameter, consist primarily of the protein actinActinActin is a globular, roughly 42-kDa moonlighting protein found in all eukaryotic cells where it may be present at concentrations of over 100 μM. It is also one of the most highly-conserved proteins, differing by no more than 20% in species as diverse as algae and humans...
. All thin filaments are attached the Z disc. - Elastic filaments, 1 nm in diameter, are made of titin, a large springy protein. They flank each thick filament and anchor it to the Z disc, the end point of a sarcomereSarcomereA sarcomere is the basic unit of a muscle. Muscles are composed of tubular muscle cells . Muscle cells are composed of tubular myofibrils. Myofibrils are composed of repeating sections of sarcomeres, which appear under the microscope as dark and light bands...
.
The protein complex composed of actin and myosin, contractile proteins, is sometimes referred to as "actomyosin". In striated muscle
Striated muscle
Striated muscle tissue is a form of fibers that are combined into parallel fibers. More specifically, it can refer to:* Cardiac muscle .* Skeletal muscle* Branchiomeric muscles...
, such as skeletal
Skeletal muscle
Skeletal muscle is a form of striated muscle tissue existing under control of the somatic nervous system- i.e. it is voluntarily controlled. It is one of three major muscle types, the others being cardiac and smooth muscle...
and cardiac muscle
Cardiac muscle
Cardiac muscle is a type of involuntary striated muscle found in the walls and histologic foundation of the heart, specifically the myocardium. Cardiac muscle is one of three major types of muscle, the others being skeletal and smooth muscle...
, the actin and myosin filaments each have a specific and constant length in the order of a few micrometers, far less than the length of the elongated muscle cell
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....
(a few millimeters in the case of human skeletal muscle
Muscle
Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...
cells). The filaments are organized into repdeated subunits along the length of the myofibril. These subunits are called sarcomere
Sarcomere
A sarcomere is the basic unit of a muscle. Muscles are composed of tubular muscle cells . Muscle cells are composed of tubular myofibrils. Myofibrils are composed of repeating sections of sarcomeres, which appear under the microscope as dark and light bands...
s.