Cell-Cell Interactions

A complete set of vocabulary flashcards covering Chapter 11 on cell-cell interactions, including cell surface components, junctions, and signaling pathways.

Unicellular organisms

Organisms that must contend with constant shifts in environmental conditions independently.

Multicellular organisms

Organisms composed of an interdependent community of cells that must communicate and cooperate.

Integral proteins

Proteins that are embedded within the phospholipid bilayer of the plasma membrane.

Peripheral proteins

Proteins that are attached to the interior or exterior surfaces of the plasma membrane bilayer.

Extracellular matrix (ECM)

A protective fiber composite secreted by most cells that helps define cell shape and attaches it to other cells.

Primary cell wall

In plants, a fiber composite secreted by new cells consisting of cellulose and gelatinous polysaccharides.

Cellulose

Long strands of polysaccharide bundled into cable-like microfibrils found in the plant primary cell wall.

Microfibrils

Bundled strands of cellulose that form a crisscrossed network in the primary cell wall of plants.

Pectin

A gelatinous polysaccharide found between microfibrils that keeps the plant cell wall moist.

Secondary cell wall

A structure secreted by mature plant cells between the plasma membrane and the primary cell wall.

Lignin

A compound found in the secondary cell wall of cells that form wood.

Waxes

Compounds found in the secondary cell wall of leaf cells.

Collagen

The fibrous protein component that makes up most of the animal extracellular matrix.

Triple helixes

Groups of collagen molecules that coalesce to form collagen fibrils.

Collagen fibrils

Structures formed from the coalescence of collagen triple helixes in the animal ECM.

Proteoglycans

Proteins attached to many polysaccharides that make up the ground substance of animal ECM and provide a rubber-like consistency to cartilage.

Tissues

Groups of similar cells that function together as a unit.

Elastin

An ECM protein that allows lung tissue to stretch.

Integrins

Membrane proteins that bind to cross-linking proteins in the ECM and anchor the cytoskeleton to the ECM.

Laminins

Cross-linking proteins in the ECM that bind to integrins to attach the ECM to the plasma membrane.

Middle lamella

A layer comprised of gelatinous pectins that glues adjacent plant cells together.

Tight junctions

Cell–cell attachments that form a belt-like seal between adjacent animal cells to prevent leaks.

Desmosomes

Strong cell–cell attachments common in animal epithelial and muscle cells that link cytoskeletons via cadherins.

Cadherins

Cell-type specific proteins in desmosomes that extend into the ECM to bind with identical proteins on adjacent cells.

Intermediate filaments

Cytoskeletal elements inside the cell that link to cadherin proteins within desmosomes.

Gap junctions

Communication portals in animal tissues that form channels for the flow of small molecules and ions between cells.

Plasmodesmata

Gaps in plant cell walls where the plasma membranes, cytoplasm, and smooth ER of two cells connect.

Hormones

Information-carrying molecules secreted from a cell that circulate in the body and act on distant target cells.

Neurotransmitters

Signaling molecules that may open or close channels in distant cells.

Lipid-insoluble signals

Signaling molecules that do not cross the plasma membrane and must be recognized by receptors at the cell surface.

Lipid-soluble signals

Signaling molecules that diffuse across the plasma membrane and bind to receptors in the target cell cytoplasm.

Signal transduction

The process of converting an extracellular signal into an intracellular signal.

G-protein-coupled receptors (GPCRs)

Receptors that, when activated, trigger the production of a second messenger via a G protein.

G protein

A protein that, once activated by a receptor, can activate molecules like adenylyl cyclase to cause signal transduction.

Second messenger

A small molecule or ion produced inside a cell that carries the signal from the receptor to the interior.

Adenylyl cyclase

An enzyme that converts $ATP$ into the second messenger $cAMP$ in response to G protein activation.

$$cAMP$$

A common second messenger produced in the signal transduction pathway of G-protein-coupled receptors.

Protein kinase A

An enzyme activated by $cAMP$ that phosphorylates other proteins.

Enzyme-linked receptors

Transmembrane proteins that directly catalyze a reaction inside the cell after binding a signaling molecule.

Receptor tyrosine kinases (RTKs)

The best-known group of enzyme-linked receptors involved in dimerization and phosphorylation.

Dimer

The structure formed by two RTK subunits after a hormone binds to them.

$$ATP$$

The molecule used to phosphorylate RTKs and the precursor for producing $cAMP$.

Ras protein

A protein activated by a bridge from an RTK that kemudian initiates a phosphorylation cascade.

Phosphorylation cascade

A series of protein kinases that sequentially phosphorylate and activate one another to trigger a cellular response.

Mitogens

Signaling molecules that often initiate phosphorylation cascades.

MAPKs

Mitogen-activated protein kinases that serve as signaling molecules to activate cell division.

Phosphatases

Enzymes that remove phosphate groups from proteins in a phosphorylation cascade to deactivate the signal.

Crosstalk

The complex signaling network formed when different transduction pathways intersect and connect.

Quorum sensing

Signaling pathways in unicellular organisms that allow coordination of activities based on population density.

Biofilm

A community of microbes, such as dental plaque, glued to a surface as a result of quorum sensing.