Biochemistry Chapter: Muscle and Muscle Proteins

Skeletal and cardiac muscles are striated, characterized by repeating patterns visible under microscopy.

The fundamental repeating unit of muscle fiber, responsible for contraction.

Long, cylindrical structures within muscle fibers, consisting of repeating sarcomeres.

A protein forming the thick filaments in muscle fibers, crucial for muscle contraction.

A protein forming the thin filaments in muscle fibers, interacting with myosin for contraction.

Myosin V is a motor protein involved in vesicle transport, commonly studied as a model for other myosin types.

Myosin V's head is longer than muscle myosin's head, facilitating its function.

Myosin head orientation alternates between "leading" and "lagging" during movement along actin filaments.

Calcium influx triggers muscle contraction.

Troponin changes shape, allowing tropomyosin to shift on actin, exposing binding sites for myosin.

Myosin thick filaments are bipolar, containing areas for parallel and antiparallel interactions.

Actin filaments attach to Z-discs (Z-lines), aided by Cap Z and alpha-actinin.

Titin and Nebulin are large proteins that act as 'molecular rulers' influencing the organization and positioning of filaments within the sarcomere. Titin maintains center position of thick filaments, and Nebulin aligns thin filaments with troponin and tropomyosin.

Shortening of the I-band during a muscle contraction, while the A-band remains the same length.

Different parts of the myosin molecule. They have unique roles in muscle function, for example, affecting force generation.

The amount of force generated by myosin during contraction, often measured in piconewtons (pN).

Experiments used to watch or measure myosin's movement.

A technique to measure forces by trapping and moving small objects using focused light beams.

The repeating pattern of myosin's interaction with actin, leading to muscle contraction.

The repeating pattern of actin subunits along the actin filament.

The distance myosin moves along an actin filament in one step.

Flexibly joining parts of myosin essential for movement during contractions.

Structures composed primarily of actin protein, forming part of the contractile apparatus in muscle cells.

Structures primarily made of myosin, interacting with thin filaments during muscle contraction.

The end of actin filament where new actin subunits are added and removed more readily during muscle contraction.

The end of actin filament where fewer actin subunits are added or removed. Active in muscle contraction.

Different forms of the actin protein, often specific to different tissues or cell types.

Different classes of myosin proteins with diverse functions beyond muscle contraction.

There are three types of animal muscle: striated (skeletal), cardiac (heart muscle), and smooth muscle (found in blood vessels, intestines, and skin).

A myofibril is a long, cylindrical structure found within muscle fibers. It is made up of repeating units called sarcomeres, which are responsible for muscle contraction.

A sarcomere is the basic functional unit of a muscle fiber. It is the repeating unit within a myofibril and is responsible for muscle contraction. It is composed of thick filaments (myosin) and thin filaments (actin).

The A band is the dark band in a sarcomere, containing the thick filaments (myosin). The I band is the light band, containing the thin filaments (actin).

The Z-disc is a protein structure that anchors the thin filaments (actin) in a sarcomere. It acts as a boundary between sarcomeres.

The M-line is a protein structure located in the center of the A band in a sarcomere, providing support for the thick filaments (myosin).

During muscle contraction, the thin filaments (actin) slide past the thick filaments (myosin) using energy from ATP, shortening the sarcomere and causing muscle contraction.

The I-band shortens during muscle contraction because the thin filaments (actin) slide past the thick filaments (myosin) towards the center of the sarcomere, eventually disappearing in a fully contracted state.

Actin is found in all cells of all animals. It's a key player in cell movement and plays a crucial role in muscle contraction.

There are different versions of the actin protein (isoforms) found in various tissues. For instance, skeletal, cardiac, and smooth muscle have their own unique actin isoforms.

An actin filament has two distinct ends: the barbed end (plus end) and the pointed end (minus end). The barbed end is where movement happens, while the pointed end is a bit more stable.

Myosin is a motor protein that acts like a tiny engine, using energy to move along actin filaments. It's essential for muscle contraction, as well as other cellular processes.

There are many different families of myosin, each with its own unique function. These families help cells move, transport cargo, and perform other vital tasks.

Thick filaments in muscle fibers are made up primarily of myosin II. These filaments interact with actin filaments to produce muscle contraction.

Thick filaments are bipolar, meaning they have two poles. This structure allows them to interact with actin filaments in a coordinated manner, essential for muscle contraction.

The myosin head is the part of the myosin protein that binds to actin and generates force. It undergoes a cycle of binding, pulling, and releasing actin, which drives muscle contraction.

The sarcomere is the basic unit of muscle contraction. It's a repeating structure within muscle fibers containing both thick and thin filaments, arranged in a specific pattern.

The Z line is a structural element at the ends of the sarcomere. Actin filaments attach to the Z line, providing a framework for muscle contraction.

Myosin V is a type of motor protein commonly used to understand how myosins work. It is found in many tissues, particularly abundant in the brain and nervous system, and plays a crucial role in transporting vesicles within cells.

Myosin V's head domain is twice as long as the head domain of muscle myosin. This difference in size allows Myosin V to move processively along actin filaments, meaning it takes large steps without detaching.

Calcium ions (Ca2+) play a crucial role in initiating muscle contraction. When calcium levels increase, it triggers a cascade of events that allow myosin to bind to actin and generate force.

Titin and nebulin are large proteins that help organize the structure of the sarcomere, the functional unit of muscle. Titin acts as a spring, holding the thick filament in place, while nebulin aligns the thin filaments precisely.

During muscle contraction, the I-band, the region containing only thin filaments (actin), shortens while the A-band, containing both thick and thin filaments, remains the same length.

Myosin S1, a subdomain of myosin, generates a force of approximately 0.2 pN (piconewtons) when interacting with actin filaments.

The importance of matching the arrangement of actin subunits with the movement of the myosin head to ensure a straight, coordinated movement of thin filaments.