Signalling molecules (memorising )

Signalling Molecules

Chemicals that mediate communication between cells.

Hydrophilic

Substances that are soluble in aqueous solutions like blood and lymph.

Hydrophobic

Substances that are insoluble in aqueous solutions and require transport proteins.

Peptides

Hydrophilic signalling molecules. single amino acids: glutamic acid (decarboxylated to gaba) aspartic acid, cysteine. True peptides: have to be made from two or more amino acids including the hormone oxytocine and neurotransmitter endorphins.

biogenic Amines

Signalling molecules derived from amino acids; can be hydrophilic or hydrophobic. Catecholamines are derivatives of tyrosine, and include dopamine, octopamine, norepinephrine, and epinephrine. Thyroxine is a derivative of the tyrosine derivative thyronine also known as thyroid hormone. it is the only hydrophobiic amine. indoleamines are derivatives of tryptophan, and include: serotonin and melatonin. acetylcholine is a derivative of choline. Histamine is a derivative of histidine and is used in immune response.

Steroids

Hydrophobic signalling molecules derived from cholesterol, functioning as hormones.

Lipids

Hydrophobic signalling molecules, including eicosanoids, that play various roles in cell signalling.

Purines

Class of signalling molecules including adenine and guanine, acting as neurotransmitters and neuromodulators.

Gases

Hydrophilic signalling molecules like nitric oxide that diffuse freely across cell membranes.

Exocytosis

The process by which signalling molecules are released from cells via vesicles.

Ionotropic receptor

A type of cell surface receptor that changes ion flow across the membrane upon ligand binding.

Metabotropic receptor

A type of cell surface receptor that changes enzyme activity within the cell, activating intracellular signalling pathways upon ligand binding.

Protease/peptidase

Enzymes that degrade signalling peptides to stop their action. Takes seconds to hours depending on whether it is a simple or glycoprotein. They regulate cellular communication and signaling.

Catecholamines

Biogenic amines derived from tyrosine, all of which are hydrophilic. examples include dopamine, noradrenaline, octopamine and adrenaline

Indoleamines

Biogenic amines derived from tryptophan, including serotonin and melatonin. serotonin acts via 5ht receptors in the membrane and plays a role in mood regulation. 5HT can be metabolised into melatonin, a neurotransmitter that regulates the circadian rhythym

Histamine

A biogenic amine derived from histidine, functioning as a neurotransmitter and paracrine signal.. In the vascular tissue, it results in vasodilation whereas in the bronchus, it results in bronchoconstriction. Is also a well known chemoattractant for mast cells (which produce further histamine) and is strongly associated with allergic responses

Acetylcholine

A neurotransmitter derived from choline. acts via the plasma membrane receptors. Nicotinic ACh receptors are ionotropic and respond to signal binding by allowing ion flux into the receiver cell. Metabotropic ACh receptors function by altering the metabotropic receptor GPCR.

Thyroid hormones

Hydrophobic hormones unique to vertebrates that increase basal metabolic rate by binding to nuclear receptors. they require a carrier protein such as albumin.

Cholesterol

A hydrophobic molecule that serves as a precursor for steroid synthesis.

Eicosanoids

Hydrophobic signalling molecules derived from arachidonic acid, mediating inflammation.

Prostaglandins

Eicosanoids that act locally in the inflammatory cascade, mediating both inflammation and nociception

Leukotrienes

Eicosanoids involved in the inflammatory response, derived from arachidonic acid.

Arachidonic acid

A 20-carbon fatty acid that serves as a substrate for eicosanoid synthesis.

Phospholipase A2 (PLA2)

An enzyme that liberates arachidonic acid from membrane phospholipids in the first step of eicosanoid synthesis

NSAIDs

Non-steroidal anti-inflammatory drugs used to inhibit prostaglandin synthesis by inhibiting its PTGS / COX enzymes. e.g. ibuprofen, aspirin, paracetamol.

G-protein-coupled receptors (GPCRs)

A family of membrane receptors that transmit signals through G-proteins.

Ligand-dependent transcription factors

Nuclear receptors activated by binding of steroid hormones to regulate gene expression.

Cyclic adenosine monophosphate (cAMP)

An intracellular second messenger involved in signal transduction.

Adenosine

A purine nucleoside that acts as a neurotransmitter and neuromodulator.

Nitric oxide (NO)

A gaseous signalling molecule involved in vasodilation, synthesized from arginine.

Soluble guanylate cyclase

An enzyme activated by nitric oxide to produce cGMP, leading to muscle relaxation.

Post-translational modification

Chemical modifications occurring after protein synthesis that affect the protein's function.

Endocrine hormones

Hormones secreted into the bloodstream to act on distant target cells.

Autocrine signals

Signals that act on the same cell that secretes them.

Paracrine signals

Signals that act on nearby cells.

Vasodilation

The widening of blood vessels, decreasing blood pressure.

Vasoconstriction

The narrowing of blood vessels, increasing blood pressure.

Secretion

The process of releasing substances from cells into the extracellular environment.

Half-life

The time it takes for the concentration of a substance in the body to reduce by half.

Transcription factor

A protein that binds to specific DNA sequences to regulate gene expression.

Signal transduction pathway

A series of molecular events initiated by a signal that leads to a cellular response.

Endocytosis

The cellular process of engulfing substances into the cell.

Phosphorylation

The addition of a phosphate group to a molecule, often regulating its activity.

Degradation

The breakdown of signalling molecules to terminate their effects.

Mitochondria

Cell organelles involved in energy production and steroid hormone synthesis.

Golgi apparatus

An organelle involved in modifying, sorting, and packaging proteins for secretion.

Rough Endoplasmic Reticulum (RER)

The organelle where peptide signalling molecules are translated from mRNA.

Lipophilic

Refers to substances that are soluble in lipids and can easily cross cell membranes.

Eicosanoid synthesis

The process of producing signalling molecules from arachidonic acid.

Thyroxine Binding Globulin

A carrier protein that transports thyroid hormones in the blood.

Cyclic guanosine monophosphate (cGMP)

A secondary messenger involved in relaxing smooth muscle cells.

Chronic pain syndromes

Long-lasting pain conditions that may involve purinergic signalling.

Ion flux

The movement of ions across a cell membrane in response to signals.

Ligand

A molecule that binds to a receptor to initiate a signal.

Post-synaptic receptor

Receptors located on the receiving side of a synaptic connection.

Chemical messenger

Any molecule that transmits a signal to elicit a cellular response.

Carrier protein

A protein that transports hydrophobic molecules in the blood.

Hydrophobic effect

The tendency of hydrophobic molecules to aggregate in aqueous environments.

Synthetic glucocorticoids

Man-made steroids used to reduce inflammation.

Cyclooxygenase (COX)

Enzymes involved in the synthesis of prostaglandins from arachidonic acid.

Calcium signaling

The use of intracellular calcium concentrations to transmit biological signals.

Glucocorticoids

A class of steroid hormones that regulate glucose metabolism and immune response.

Transmembrane receptor

A receptor that spans the cell membrane and transmits signals from outside to inside.

Signal amplification

The process by which a small number of signaling molecules can produce a large effect.

Cells of the immune system

Cells that help defend the body against infections and diseases.

Dopamine

This neurotransmitter is found in vertebrates

octopamine

this neurotransmitter is found in invertebrates

noradrenaline

vertebrate neurotransmitter

adrenaline

paracrine and endocrine hormone in vertebrates that plays a key role in the fight-or-flight response.

LIPIDS: (PG’s) and (TX’s) – synthesised by the action of (COX) / _ (PTGS) enzymes.

(LT’s), (HETE’s), (HPETE’s), and lipoxins – synthesised by the (LOX) __ enzymes.

Prostaglandins , Thromboxanes, cyclooxygenase, prostaglandin synthase. Leukotrienes, Hydroxyeicosatetraenonic acids, Hydroperoxyeicosatetraenonic acids, lipoxygenase

Prostoglandins and leukotrienes

Prostoglandin - made in prostate gland. Leukotrienes - made in leukocytes. Mediate inflammatory cascade, immune response by signalling immune cells and vascalature.