BGM2002: Introduction to Cell Signalling

Comprehensive vocabulary flashcards covering the basic principles, modes of communication, signal types, three steps of cell signaling, and pathway characteristics from Lecture 1 of BGM2002.

Cell Signalling

A complex system of communication that governs basic cellular activities, coordinates cell actions, and enables cells to perceive and correctly respond to microenvironmental changes.

Apoptosis (Signalling Context)

Programmed cell death that most cells undergo as a default pathway when deprived of necessary survival signals.

Gap Junctions

Direct cytoplasmic channels between adjacent cells formed by aligning membrane proteins that facilitate metabolic and electrical coupling through the direct exchange of ions and small signaling molecules.

Antigen Presenting Cell (APC) Direct Contact Signalling

A form of contact-dependent communication where an immune cell (such as a macrophage) displays foreign antigen fragments bound to MHC2 on its surface to be recognized directly by the $\text{CD4}^+$ receptor on a helper T cell.

Autocrine Signalling

A mode of communication where a cell secretes signaling molecules into the extracellular fluid that bind to receptors located on its own surface (e.g., $\text{IL-1}$ secreted by monocytes, or survival factors secreted by tumor cells).

Paracrine Signalling

Short-range communication where a signaling cell releases local mediators into the extracellular fluid to act on neighboring target cells (e.g., Wnt and Hedgehog signaling pathways).

Tumour-Macrophage Paracrine Loop

A reciprocal local signaling circuit where tumor-associated macrophages (TAMs) secrete epidermal growth factor (EGF) to activate EGFR and drive cancer cell invasiveness, while breast tumor cells produce colony-stimulating factor 1 (CSF1) to recruit and stimulate TAMs via CSF1R.

Neuronal Signalling (Synaptic Signalling)

A rapid, specialized communication process where electrical impulses along an axon trigger the release of chemical neurotransmitters across a synaptic cleft to bind receptors on an adjacent neuron, muscle, or gland cell.

$$\beta\text{-Endorphins}$$

Endogenous neuropeptides that suppress pain signals during neuronal transmission by blocking either neurotransmitter secretion or post-synaptic reception.

Endocrine Signalling

A slow, long-distance communication mechanism in which specialized endocrine cells secrete hormones into the bloodstream to reach distant target cells expressing matching receptors.

Cell-Surface Receptors vs. Intracellular Receptors

Cell-surface transmembrane receptors detect large, hydrophilic molecules that cannot penetrate the lipid bilayer, whereas intracellular receptors detect small, hydrophobic molecules (e.g., estradiol) or dissolved gases (e.g., $\text{NO}$) that freely cross the plasma membrane.

Signal Reception

The initial step of cell signaling wherein an extracellular signaling molecule (ligand) binds with high affinity to a complementary specific receptor protein.

Signal Transduction

The second stage of cell signaling wherein receptor activation triggers an intracellular cascade of transducers and second messengers that relay, integrate, distribute, and amplify the signal throughout the cell.

Effector Proteins

Downstream target proteins activated at the end of a signaling pathway—such as metabolic enzymes, transcription regulatory proteins, or cytoskeletal proteins—that directly execute altered cellular metabolism, gene expression, or shape and motility.

Signalling Specificity

The precision of signaling ensured by high-affinity binding between a signaling molecule and its receptor, along with restricted expression of particular receptors and downstream machinery to distinct cell types.

Signal Integration

The convergence and coordination of multiple simultaneous extracellular and intracellular signals sharing common relay molecules to produce a harmonized physiological response.

Signal Amplification

The multiplication of signal strength within a transduction cascade, allowing very low concentrations of an extracellular ligand to generate robust intracellular responses that rise clearly above background noise.

Positive Feedback Loop

A regulatory mechanism in which a downstream component or output of a signaling pathway acts back upstream to stimulate its own production or amplify the pathway's activity.

Negative Feedback Loop

A regulatory mechanism in which an output or downstream product of a signaling cascade acts back upstream to inhibit the pathway, terminating the response and maintaining homeostasis.

Adaptation (Desensitisation)

The reversible reduction of a cell's sensitivity to a persistent or prolonged signaling stimulus, commonly achieved through negative feedback mechanisms such as receptor phosphorylation, endocytosis, or degradation.