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What are ligands and where do they come from?
Ligands are signaling molecules released from signaling cells that bind to receptor proteins on target cells.
What are the four types of signaling mechanisms?
Autocrine, Direct Signaling, Paracrine, and Endocrine.
In the autocrine signaling mechanism, where does the ligand bind?
The ligand binds to the receptor in the signaling cell.
How does ligand transfer occur in direct signaling?
Ligands travel from cytoplasm to cytoplasm from the signaling cell to the target cell.
What type of cells do ligands bind to in paracrine signaling?
Ligands bind to nearby cells in paracrine signaling.
What ensures that the signal is local in paracrine signaling?
Rapidly degraded ligands ensure that the signal is local.
In endocrine signaling, where do ligands bind?
Ligands bind to receptors on distant cells in endocrine signaling.
What ensures that ligands can travel across the body in endocrine signaling?
Stable ligands ensure they can travel across the body.
What is an example of a ligand?
Hormones and neurotransmitters.
What kind of receptor is located in the cytoplasm of the cell?
Intracellular receptor.
What type of ligands do intracellular receptors require?
Ligands must be small and hydrophobic to diffuse across the membrane.
What is an example of a ligand that binds to intracellular receptors?
Steroid hormones.
Where are cell surface receptors located?
Cell surface receptors are on the surface of the cell, anchored in the plasma membrane.
What are the three distinct domains of cell surface receptors?
Extracellular Domain, Intracellular Domain, Transmembrane Domain.
What is the function of the extracellular domain of cell surface receptors?
It is exposed to the outside of the cell.
What happens when a ligand binds to a receptor?
It leads to a change in shape of the receptor and alters its behavior.
What is phosphorylation?
The modification of protein by the addition of phosphate group(s) from ATP.
What class of enzymes catalyzes the transfer of phosphate group in Phosphorylation?
Kinases.
What is dephosphorylation?
The removal of a phosphate group(s) from a protein.
What class of enzymes catalyzes dephosphorylation?
Phosphatases.
How can the function of a protein be affected?
The function can be switched on/off depending on its phosphorylation state.
What are some potential results of signal transduction?
Altered cell behavior, cell growth/division, apoptosis (programmed cell death).
What do single-celled yeasts secrete to find other yeast cells?
They secrete a 'mating factor' ligand.
What is quorum sensing in bacteria?
It's the ability of bacteria to communicate cell density and form structures like biofilms.
What are 'autoinducers' in bacterial communication?
Ligands released by bacteria to communicate cell density.
What happens at low ligand density in quorum sensing?
The ligand diffuses, but there is no response.
What happens at high ligand density in quorum sensing?
The signaling pathway is activated and biofilm formation occurs.