C2.1 Chemical signalling (HL) Notes

Receptor

A protein that detects and responds to specific signals, binding to signalling molecules (ligands) to initiate a cellular response.

Ligand

A molecule that binds to a specific site on a receptor protein.

Quorum Sensing

A communication system used by bacteria to coordinate group behaviors based on population density through the release and detection of signaling molecules.

Hormone

Chemical messengers secreted by endocrine glands into the bloodstream to regulate physiological processes.

Neurotransmitter

Chemical signals used by neurons to communicate across synapses, the tiny gaps between nerve cells.

Cytokine

Small proteins that mediate and regulate immune responses, inflammation, and cell signaling.

Calcium ions (Ca²⁺)

Universal signaling molecules involved in a wide range of cellular processes, from muscle contraction to neurotransmitter release.

Signal transduction

The process by which cells respond to external signals, converting them into a cascade of chemical responses inside the cell.

Transmembrane receptors

Receptors that span the plasma membrane and interact with signaling molecules that cannot cross the membrane.

Intracellular receptors

Receptors located within the cytoplasm or nucleus that interact with signaling molecules that can cross the plasma membrane.

G-Protein-Coupled Receptors (GPCRs)

A large family of transmembrane receptors that detect external signals and activate intracellular G proteins.

Receptor Tyrosine Kinase (RTK)

A type of transmembrane receptor that has an enzymatic domain capable of phosphorylating tyrosine residues on itself or other proteins.

Epinephrine (Adrenaline)

A hormone that prepares the body for action by triggering rapid physiological changes.

cAMP (cyclic AMP)

A second messenger that relays signals within cells, amplifying the signal from hormones like epinephrine.

Insulin

A peptide hormone produced by the pancreas that regulates blood glucose levels by promoting its uptake in cells.

Oestradiol

A form of estrogen that regulates the menstrual cycle and promotes the growth of the uterine lining.

Progesterone

A steroid hormone that maintains the uterine lining and is critical for pregnancy.

Tyrosine kinase activity

The ability of certain receptors to phosphorylate tyrosine residues on themselves or other proteins, initiating a signaling cascade.

Positive feedback

A process where the end product of a reaction enhances its own production, creating a self-reinforcing cycle.

Negative feedback

A process where the end product of a reaction inhibits its own production, helping to maintain stability.

Membrane potential

The difference in electrical charge across the plasma membrane of a cell.

Depolarization

A change in the membrane potential, making it less negative, often triggered by the influx of positive ions.

Autophosphorylation

The process by which a tyrosine kinase receptor phosphorylates its own tyrosine residues after ligand binding.

Signal amplification

The process by which a small initial signal leads to a larger cellular response, often through secondary messengers.

Hormone response element (HRE)

Specific DNA sequences to which hormone-receptor complexes bind to initiate gene transcription.

Gene expression

The process by which information from a gene is used to synthesize a functional gene product, usually protein.

Feedback inhibition

A regulatory mechanism in which the end product of a metabolic pathway inhibits an enzyme involved in its production.