IB Bio C2.1

Receptors

Proteins located on cell surface membranes or inside cytoplasm that bind to specific signaling molecules.

Ligands

Signaling chemicals that bind to receptors and trigger signal transduction.

Signal transduction

The process by which binding of a ligand to a receptor triggers a change in cellular activity.

Specificity

The ability of receptors to bind only one type of signaling molecule.

Autoinducers

Chemical signals released by bacteria for quorum sensing.

Quorum sensing

Bacterial communication based on population density.

Hormones

Long-distance signaling molecules that travel via the bloodstream.

Neurotransmitters

Fast, local signaling molecules that transmit signals across synapses.

Cytokines

Immune signaling molecules that regulate inflammation and immune responses.

Calcium ions (Ca²⁺)

Intracellular second messengers that trigger rapid responses.

Hydrophilic ligands

Water-soluble signaling molecules that bind to transmembrane receptors.

Hydrophobic ligands

Lipid-soluble signaling molecules that can diffuse through membranes to bind intracellular receptors.

Transmembrane receptors

Receptors that are embedded in the plasma membrane and bind to hydrophilic ligands.

Intracellular receptors

Receptors located inside the cell that bind to hydrophobic ligands.

G protein-coupled receptors (GPCRs)

Transmembrane receptors that detect external signals and activate G proteins.

Epinephrine

A hormone and neurotransmitter that increases heart rate and mobilizes glucose during stress.

Tyrosine kinase receptors

Receptors with built-in enzyme activity that phosphorylate tyrosine residues on proteins.

Insulin

A protein hormone that lowers blood glucose by facilitating its uptake into cells.

Oestradiol

A steroid hormone that regulates female secondary sex characteristics and menstrual cycles.

Progesterone

A steroid hormone that prepares and maintains the uterus for pregnancy.

Positive feedback

A process where the response enhances the original signal, amplifying the pathway.

Negative feedback

A process where the response reduces the original signal, maintaining homeostasis.

Gene expression

The process by which specific genes are activated or repressed, affecting protein synthesis.

Second messengers

Molecules that relay signals received at receptors on the cell surface to target molecules inside the cell.

Signal cascade

A series of events inside a cell triggered by receptor activation that leads to a cellular response.

Receptor dimerization

The joining of two receptor units, common in tyrosine kinase receptors.

Hormone response elements

Specific DNA sequences where hormone-receptor complexes bind to regulate gene transcription.

Bioluminescence

The production of light by living organisms, as demonstrated by Vibrio fischeri.

Facilitated diffusion

The process by which substances cross membranes with the assistance of special proteins.

Glycogen breakdown

The process of converting glycogen into glucose, activated by adrenaline signaling.

Cellular responses

Changes in cellular activity or function triggered by signal transduction pathways.

Homeostasis

The maintenance of stable internal conditions in a biological system.