Cellular Biology: Cytoskeleton, ECM, Cell Wall, Cell Size, and Viruses

Vocabulary flashcards covering cellular cytoskeleton components, extracellular matrix, cell walls across organisms, limits on cell size, and viral structures.

Cytoskeleton

A network of protein fibers that organizes structures and activities in the cell, comprising microtubules, microfilaments, and intermediate filaments.

Microtubules

Hollow tubes composed of $\frac{\alpha}{\beta}$-tubulin dimers ($\alpha\text{-tubulin}$ and $\beta\text{-tubulin}$) that maintain cell shape, assist in chromosome movement during cell division, power cilia and flagella, and serve as tracks for organelle movement.

Centrosome

The microtubule-organizing center in animal cells that contains two centrioles, copies prior to cell division, and serves as the origin for spindle fibers.

Centriole

A cellular structure made up of $27$ microtubules; a pair of centrioles forms the centrosome in animal cells.

Flagella

Locomotor appendages present in small numbers (one or a few per cell) that generate force parallel to their axis via an undulating motion.

Cilia

Short, highly numerous cellular projections used for locomotion or moving fluid across a cell surface through oar-like power and recovery strokes.

Microfilaments

Thin, twisted filaments composed of the protein actin that function in maintaining cell shape, bearing tension (pulling forces), muscle contraction, and vesicular movement.

Myosin

A motor protein that uses ATP to walk along actin microfilaments, sliding filaments relative to each other during muscle contraction and moving vesicles.

Kinesin

A motor protein that utilizes ATP to move cargo vesicles along microtubules toward their plus ends.

Intermediate Filaments

Sturdy, cable-like cytoskeletal fibers made of coiled proteins (such as keratins) found in some animals, responsible for maintaining cell shape and anchoring organelles such as the nucleus.

Extracellular Matrix (ECM)

An extracellular structure in animal cells consisting of structural proteins embedded in a proteoglycan network that provides support, determines tissue architecture, and regulates cell behavior.

Collagen

A glycoprotein component of the animal ECM embedded in proteoglycans, representing approximately $40\%$ of all protein in the human body.

Fibronectin

An extracellular glycoprotein that attaches animal cells to the extracellular matrix by binding to integrins.

Integrins

Cell-surface receptor proteins (integral membrane proteins) that bind to fibronectin on the outside and cytoplasm microfilaments on the inside, transmitting mechanical and chemical signals between the ECM and cytoskeleton.

Cell Wall

A rigid external layer surrounding the plasma membrane in plants, fungi, bacteria, and some protists that provides structural support, protection, and resists internal fluid pressure.

Turgor Pressure

The force exerted by water pressing against the cell wall when a plant cell takes up water in a hypotonic environment.

Peptidoglycan

The principal structural reinforcing material that makes up bacterial cell walls.

Cellulose

The primary reinforcing material present in the cell walls of plants and plant-like protists.

Chitin

The structural reinforcing material found in the cell walls of fungi and fungi-like protists.

Surface-to-Volume Ratio

The physical constraint limiting cell size, where material exchange capacity is proportional to surface area while metabolic demands are proportional to volume.

Viruses

Acellular obligate parasites containing genetic material (DNA or RNA) enclosed in a protein capsid (and sometimes a host-derived lipid envelope) that rely entirely on host cell machinery to reproduce.