Cell Signaling, Cell Size, Cytoskeleton, and Extracellular Matrix

Vocabulary flashcards covering cell signaling receptors, signal amplification, second messengers, surface area-to-volume ratio constraints, cytoskeletal elements, motor proteins, and the extracellular matrix.

Three Membrane Receptor Types

The three major classes of cell-surface receptors: gated ion channels, protein kinase receptors, and G protein-linked receptors.

Gated Ion Channels

Receptors that open in response to a specific signal, changing shape to allow specific ions to pass across the membrane.

Phosphorylation

A chemical reaction in which a phosphate group is transferred from one molecule to another, often catalyzed by an enzyme.

Protein Kinase Receptors

Receptors with enzymatic kinase activity that phosphorylate target proteins to initiate intracellular signal cascades.

G Protein-Linked Receptors

Receptors that utilize a G protein as an intermediate to activate downstream effector proteins when bound by a signal.

G Protein Activation

The process where GTP (3 phosphates) replaces GDP (2 phosphates) upon signal binding, causing the G protein to break up and activate an effector protein.

Signal Amplification

A mechanism connecting an initial signal to the magnitude of the cellular response through cascades involving the repeated use of kinases.

Second Messengers

Small, single molecules that amplify and distribute signals throughout the cell to elicit different reactions or turn off cellular processes.

Second Messenger Examples

Cyclic AMP, diacylglycerol, inositol triphosphate, calcium ions, and nitric oxide.

Cell Volume Extremes (Human Cell vs. Ostrich Egg)

A human cell holds a volume of roughly $0.0009\,\text{milliliters}$, whereas an ostrich egg holds $1.8\,\text{liters}$, which is $1.4\text{ billion}$ times larger.

Surface Area-to-Volume Ratio ($\text{SA:Vol}$)

A physical constraint setting an upper limit on cell size; as cell volume increases, the relative surface area available for diffusion and material exchange decreases.

Cellular Adaptations for $\text{SA:Vol}$ Constraints

Strategies used by cells to maintain sufficient exchange capacity, including increased membrane infoldings, growing in only one dimension, internal compartmentalization, or increasing the rate of transport across boundaries.

Cell Membrane

A phospholipid bilayer with embedded proteins that surrounds every cell, regulating the entry and exit of molecules and ions.

Cytoskeleton

A structural network composed of protein fibers (microfilaments, intermediate filaments, and microtubules) that provides shape, support, organelle anchoring, and cellular movement.

Microfilaments

Cytoskeletal fibers composed of actin that assist in cell support and movement.

Intermediate Filaments

Tough, ropelike cytoskeletal fibers made of fibrous proteins that help maintain cell shape and anchor organelle positions.

Microtubules

Hollow cytoskeletal tubes composed of two types of tubulin that act as tracks for organelle movement and interact with motor proteins.

Dynein

A motor protein that interacts with microtubules via ATP phosphorylation, working with nexin attachments to generate bending movements.

Kinesin

A motor protein that moves vesicles and organelles along microtubules.

Extracellular Matrix (ECM)

A network in animal cells made of collagen and proteoglycans in a gel-like medium that holds tissues together, aids cell recognition, limits volume/cell growth, acts as a barrier to infection, and provides a framework for movement.

Plant Cell Wall

A rigid external structure found outside the cell membrane in plant cells that provides structural support.