Bio exam 3 cell-cell interactions

Plasma membrane

A phospholipid bilayer studded with proteins that regulates transport and connects to internal and external structures.

Integral proteins

Membrane proteins embedded in the lipid bilayer.

Peripheral proteins

Membrane proteins attached to the surface of the bilayer.

Extracellular matrix (ECM)

A fiber composite secreted by animal cells that provides structural support, defines shape, and protects the cell.

Collagen

The main fibrous protein in the ECM that provides tensile strength.

Proteoglycans

Proteins with attached polysaccharide chains that form the gel-like ground substance of the ECM.

Integrins

Membrane proteins that connect the ECM to the cytoskeleton and transmit signals between the cell and its environment.

Laminins

Cross-linking proteins in the ECM that attach integrins to the extracellular matrix.

Elastin

A protein in the ECM that allows tissues like the lungs to stretch.

Primary cell wall

The outermost layer of a young plant cell made of cellulose microfibrils and pectin; defines shape and resists turgor pressure.

Cellulose

A polysaccharide forming the microfibrils that give strength to plant cell walls.

Pectin

A gelatinous polysaccharide in the plant cell wall that keeps it moist and flexible.

Expansins

Plant proteins that loosen the bonds between cellulose microfibrils to allow cell growth.

Secondary cell wall

A rigid layer between the plasma membrane and primary wall in mature plant cells; composition depends on cell function.

Lignin

A complex polymer in wood cells that provides rigidity and strength.

Middle lamella

A pectin-rich layer that glues adjacent plant cells together.

Tight junctions

Cell-cell attachments in animal tissues that form watertight seals between adjacent cells.

Desmosomes

Strong cell-cell adhesions that connect the cytoskeletons of adjacent cells using intermediate filaments.

Intermediate filaments

Cytoskeletal fibers that reinforce desmosomes and maintain cell structure.

Selective adhesion

The ability of cells to bind only to other cells of the same type using specific adhesion molecules.

Gap junctions

Channels that allow direct communication between adjacent animal cells through the exchange of ions and small molecules.

Plasmodesmata

Openings in plant cell walls that connect the cytoplasm of neighboring cells via shared plasma membranes.

Symplast

The shared cytoplasm between plant cells connected by plasmodesmata.

Apoplast

The extracellular space in plant tissues outside the plasma membrane.

Cell-cell signaling

Communication between cells through the release and detection of signaling molecules.

Hormone

An information-carrying molecule secreted into the bloodstream that affects distant target cells.

Neurotransmitter

A signaling molecule released by neurons to communicate with other cells.

Signal receptor

A protein that binds a signaling molecule and triggers a response in the target cell.

Lipid-soluble signal

A signaling molecule (like steroid hormones) that diffuses through the plasma membrane to bind intracellular receptors.

Lipid-insoluble signal

A signaling molecule that binds to receptors on the cell surface because it cannot cross the plasma membrane.

Signal transduction

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

Second messenger

A small molecule or ion that transmits and amplifies a signal inside the cell.

G protein

A membrane protein activated by signal receptors that triggers the production of second messengers.

GTP (guanosine triphosphate)

A molecule that activates G proteins when bound.

GDP (guanosine diphosphate)

The inactive form of a G protein when GTP is hydrolyzed.