Ch. 17 Pt. 2 - Cytoskeleton

Flashcards covering key concepts related to the structure and function of the cytoskeleton, muscle contraction, and associated diseases.

What is an intermediate filament?

A key component of the cytoskeleton, providing structural support to cells and resistance to mechanical stress.

What is G-actin?

Globular, monomeric actin.

What is F-actin?

Filamentous actin polymers.

What is treadmilling in actin filaments?

Dynamic process by which actin filaments are constantly disassembled at one end while assembled at the other.

What is a lamellipodium?

Membrane protrusion at the leading edge of moving cells.

What is a filopodium?

Thin, cytoplasmic projections of the cell membrane that help cells explore their environment and adhere to surfaces.

What role does myosin play in cells?

A molecular motor protein that converts chemical energy in the form of ATP into mechanical energy for force generation and movement.

What defines a sarcomere?

The smallest functional unit of striated muscle tissue, composed of actin and myosin filaments.

How do intermediate filaments compare to other cytoskeleton components?

They are less dynamic and the strongest component of the cytoskeleton.

What is the average diameter of intermediate filaments?

Approximately 15 nm.

What are keratin filaments?

A type of intermediate filament found in skin, nails, and hair.

What is vimentin?

An intermediate filament protein found in smooth muscle cells and fibroblasts.

What are neurofilaments?

Intermediate filaments found in neurons.

What are nuclear lamins?

Intermediate filaments that compose the nuclear lamina, providing structural support to the nuclear envelope.

What functions do intermediate filaments serve?

They aid in signal transduction, nuclear lamina formation, tissue cohesion, and provide mechanical support to cells.

How are intermediate filaments anchored to the cell membrane?

By adhesive proteins such as desmosomes and hemidesmosomes.

What is one consequence of keratin loss in the skin?

It leads to blister formation.

How do intermediate filaments contribute to heart function?

They are responsible for generating a normal sinus rhythm in the heart.

What is the role of the nuclear lamina?

It strengthens the nuclear membrane and serves as attachment sites for chromosomes.

What cycle do actin filaments undergo?

Treadmilling, where monomers are added at one end and lost at the other.

What is the significance of actin filament polarity?

It determines the growth rate, with the '+ end' primarily responsible for assembly.

What do actin-binding proteins do?

They control the dynamic nature of actin, including regulation of polymerization and depolymerization.

What is phalloidin's effect on actin?

It binds to actin filaments (F-actin) and prevents depolymerization.

How does cytochalasin affect actin?

It prevents polymerization at the '+ end' of actin filaments.

What are the two types of cellular protrusions involved in cell crawling?

Lamellipodia (thick bundles of actin) and filopodia (thin-pointed protrusions).

How do integrins link the cytoskeleton?

They bind both to the cytoskeleton and outside surfaces to create anchorage points.

What role do the Rho family of GTPases play in cell motion?

They induce actin remodeling when GTP is bound.

What are myofibrils?

Bundles within muscle fibers that are divided into repeating units called sarcomeres.

How is muscle contraction achieved?

It is dependent on the interaction of actin and myosin filaments.

What triggers muscle contraction in the presence of Ca2+?

Ca2+ causes the troponin complex to release tropomyosin, allowing myosin to bind to actin.

What are cytoskeleton defects associated with?

Diseases such as ALS, cancer, and muscular dystrophy.