Ligand
Definition
Any molecule that binds a defined site on a protein and changes what the protein does. A receptor's natural ligand is the endogenous signal; an agonist and an antagonist are both ligands with different consequences.
Where this term comes up
Entries whose definition mentions Ligand.
What this means for research sourcing
Cell-biology terms provide context for interpreting peptide research at the cellular level. See how these concepts apply to compounds Volta supplies for study.
Related Terms in Cell Biology
Enzyme
A protein that catalyses a reaction, raising its rate without being consumed. Enzymes build peptides and also destroy them, which is why proteases appear on both sides of peptide science.
Cytokine
A small secreted protein cells use to signal to one another, prominent in immune communication. Pro-inflammatory cytokines such as TNF-alpha and IL-6 are the standard readout in anti-inflammatory peptide studies.
Cell Membrane
The lipid bilayer enclosing a cell, which controls what enters and leaves. Its hydrophobic interior is the reason large polar molecules such as peptides need a receptor or a transporter rather than simply diffusing in.
Nucleus
The membrane-bound compartment holding a cell's DNA, where transcription happens. Peptides acting at surface receptors reach it only indirectly, through signalling cascades that end in a transcription factor.
Mitochondria
The organelles that generate most of a cell's ATP through oxidative phosphorylation. They carry their own small genome, which is where the mitochondrial-derived peptides are encoded.
Ribosome
The machine that reads messenger RNA and assembles proteins from amino acids. Synthetic peptides bypass it entirely, which is why a synthetic sequence can contain D-amino acids and unnatural residues that no ribosome would incorporate.
Endoplasmic Reticulum (ER)
The folded membrane network where secreted and membrane proteins are assembled and folded, and where lipids are made. A targeting sequence is what routes a nascent protein into it.
Golgi Apparatus
The stack of membranes that finishes proteins arriving from the ER, adding or trimming sugars and sorting them to their destinations. Many peptide hormones are cut from a larger precursor on the way through it.