9. Motility and contractility

Motility

The ability of an organism or cell to move by itself, through various mechanisms at the tissue, cellular, and subcellular levels.

Microtubules (MTs)

Cytoskeletal structures that provide a rigid set of tracks for transport of organelles and vesicles within cells.

Contractility

The ability of muscle cells to shorten and generate force, a specialized form of motility.

Motor proteins

Proteins that convert chemical energy (ATP) into physical movement by altering their shape and attachment to scaffolding.

Myosin

A type of motor protein that interacts with actin filaments to facilitate muscle contraction.

Dyneins

Motor proteins that transport materials toward the minus ends of microtubules, involved in cellular movement such as cilia and flagella.

Kinesins

Motor proteins that move toward the plus ends of microtubules and are involved in processes like fast axonal transport.

Chemotaxis

Directional movement of a cell in response to a chemical stimulus, often involving diffusible cues like chemoattractants and chemorepellants.

Integrins

Transmembrane proteins that mediate attachment between cells and the extracellular matrix, playing a critical role in cell movement.

Sliding filament theory

The model that explains muscle contraction through the sliding of thick (myosin) and thin (actin) filaments past each other.

Calcium regulation in muscle contraction

Process where calcium ions bind to troponin, leading to a conformational change that uncovers myosin-binding sites on actin.

Troponins

Proteins bound to actin filaments that regulate muscle contraction by controlling access of myosin to actin.

Sarcoplasmic reticulum (SR)

Specialized endoplasmic reticulum in muscle cells that stores and releases calcium ions necessary for muscle contraction.

Cilia and Flagella

Cell structures that facilitate locomotion or movement of fluids; cilia are short and numerous, while flagella are longer and fewer.

Axoneme

The structural arrangement of microtubules in cilia and flagella, responsible for their beating motion.

Rho GTPases

Molecules that regulate cytoskeletal changes affecting cell shape, motility, and attachment through activation pathways.

Smooth Muscle

Involuntary, non-striated muscle found in the walls of hollow organs, responsible for slow, prolonged contractions.

Ryanodine receptors (RyR)

Calcium channels in muscle cells that mediate calcium release from the sarcoplasmic reticulum during contraction.