IndietroGeneral Biology: Cell Signaling and Metabolism - Enzyme Structure and Regulation
Termini in questo insieme (24)
Paracrine signaling is the secretion of a signal molecule by a cell into the local environment, affecting nearby cells in the immediate vicinity.
A neurotransmitter acts as a signal molecule that binds to receptors and triggers a response, such as opening gated ion channels in neurons.
G protein-coupled receptors (GPCRs), channel-linked receptors, and receptor tyrosine kinases (RTKs) are all transmembrane receptors.
Receptor tyrosine kinases (RTKs) undergo dimerization when a ligand binds; GPCRs and channel-linked receptors do not.
A second messenger is a small molecule that relays signals inside the cell, such as cyclic AMP (cAMP).
Adenylyl cyclase converts ATP to cyclic AMP (cAMP), which acts as a second messenger in the signaling pathway.
G protein → adenylyl cyclase → cAMP → protein kinase A.
Multiple steps allow for signal amplification, increasing the cellular response to a single signal molecule.
Kinases add phosphate groups to target proteins, activating or modifying their function.
Phosphatases remove phosphate groups, inactivating proteins and turning off signal transduction.
Catabolism is the cellular process of breaking down large molecules into smaller ones, releasing energy.
Hydrolysis breaks bonds by adding water; dehydration synthesis forms bonds by removing water.
They have enzymes with high optimal temperatures that remain functional at elevated heat.
Activation energy is the energy barrier that reactants must overcome to form products.
Enzymes lower activation energy and increase the rate of chemical reactions without changing free energy.
The active site is the region of an enzyme where substrates bind and catalysis occurs.
Because enzymes become saturated when all active sites are occupied by substrate.
Increasing enzyme concentration can increase reaction rate if substrate is abundant and enzymes are not saturated.
Cofactors are non-protein molecules required for enzyme activity; organic cofactors are called coenzymes.
Feedback inhibition occurs when the end product of a metabolic pathway inhibits an earlier enzyme to regulate the pathway.
Binding of a regulatory molecule at a site other than the active site causes a conformational change that activates or inhibits enzyme activity.
Cooperativity is when binding of substrate to one subunit of a multisubunit enzyme increases substrate binding at other subunits.
A competitive inhibitor binds the active site, competing with substrate and reducing enzyme activity.
A noncompetitive inhibitor binds away from the active site, changing enzyme shape and reducing activity.