Cell Signaling & Receptors Lecture

Vocabulary flashcards covering key terms from the lecture on cell signaling pathways, receptor types, and examples such as immune responses and caffeine’s action.

Ligand

A signaling molecule that binds specifically to a receptor protein to initiate a cellular response.

Receptor Protein

Membrane-bound or intracellular protein that recognizes and binds a ligand, undergoing a conformational change that starts signal transduction.

Conformational Change

Structural alteration in a receptor after ligand binding that enables downstream signaling events.

Signal Transduction Cascade

Series of sequential intracellular events triggered by an activated receptor, leading to a cellular response.

Affinity (for a ligand)

The strength of binding between a ligand and its receptor; higher affinity means tighter, more likely binding.

Fight-or-Flight Response

Physiological reaction mediated by epinephrine/adrenaline causing increased heart and lung rates and decreased digestion.

Epinephrine (Adrenaline)

Hormone that triggers the fight-or-flight response, producing different effects in various cell types.

Juxtacrine Signaling

Cell-to-cell communication requiring direct contact between membranes or via gap junctions/plasmodesmata.

Gap Junction

Protein channel connecting adjacent animal cells, allowing direct transfer of signaling molecules.

Plasmodesmata

Cytoplasmic channels through plant cell walls that permit direct exchange of signals and substances.

Antigen-Presenting Cell

Immune cell that engulfs a pathogen and displays its antigens on the surface to alert T cells.

T Cell

Type of immune cell that recognizes antigens presented on other cells and initiates immune responses.

Cytokine

Signaling molecule released by immune cells (often in paracrine fashion) to influence nearby cells.

Paracrine Signaling

Communication in which a cell releases signals that affect neighboring—but not directly touching—cells.

Autocrine Signaling

Process in which a cell secretes a signal molecule that binds to receptors on its own surface, stimulating itself.

Intracellular Receptor

Receptor located inside the cell that binds small, non-polar, hydrophobic ligands able to cross the membrane.

Hydrophobic Ligand

Small, non-polar signaling molecule capable of diffusing through the lipid bilayer to reach intracellular receptors.

Adenosine

Endogenous molecule that accumulates during activity and binds receptors to promote fatigue and rest.

Caffeine

Stimulant that competitively binds adenosine receptors, preventing the fatigue signal.

Ligand-Gated Ion Channel

Membrane protein that opens an ion pore upon ligand binding, allowing ions to flow into or out of the cell.

Protein Kinase Receptor

Membrane receptor that autophosphorylates its intracellular tails after ligand binding, activating downstream enzymes.

Autophosphorylation

Addition of phosphate groups to a protein kinase receptor’s own tails, enabling further signaling.