Local Signaling
Adjacent Cells, Direct Contact, Local Regulators (aka signal molecules or ligands)
Paracrine Signaling
Secretory vesicles sending signals to a target cell
Synaptic Signaling
Nerves sending a signal to a target cell
Endocrine Glands
Send hormones to the target cell through the blood stream
Signal Reception
Ligands match the shape of the protein receptors on the target cell and bind together
Signal Transduction
Ligand changes shape and the phosphorylation cascade occurs
Kineses
Enzyme that removes a phosphate from ATP and puts them on another molecule
Cellular Response
Final activated protein from a phosphorylation cascade goes into the nucleus and binds to a gene on DNA that turns the gene “on” or “off”
Steroid Hormones
Bind to intracellular receptors
G-protein-linked receptors
G-protein as a peripheral protein because GTP (guanosine triphosphate) is used instead of ATP for the first step of the phosphorylation cascade, the rest use ATP
Tyrosine Kinase Receptors
Come in pairs with phospholipids between them; separately tagged by their own ligands, move together in the plasma membrane and snap together; phosphorylated with ATP to give energy to the molecule; proteins attach to relay a cellular response
Ion (Gated) Channel Receptors
Signal molecule opens the gate for ions to flow through
Phosphorylation Cascade
A series of protein kinases add a phosphate to the next one in line, activating it; phosphate enzymes then remove the phosphates
Cyclic AMP (cAMP)
Made from ATP; can bind to a protein receptor on ER or other organelles; acts as a second messenger in cellular pathways to initiate phosphorylation cascade
Adenylyl Cyclase
Enzyme that breaks off the first two phosphates to create cAMP for it to act as a second messenger
Phosphodiesterase
converts cAMP to AMP
Inositol Triphosphate (IP3)
Can trigger an increase in Ca+2 in the cytosol
Phospholipase C
Breaks off IP3 from PIP2, leaving DAG behind
Pathway Branching
One peripheral protein tags multiple relay molecules
Cross-Talk
Occurs when one peripheral protein tags a relay molecule that was in the path of a different peripheral protein, either activating or inhibiting it
Scaffolding Proteins
Can increase the signal transduction efficiency by allowing multiple other proteins to attach
Saltatory Conduction
Opening sodium ion gates at the nodes of Ranvier
Simple Endocrine Pathway
Catalyzed by a protein (no nerves) → hormone
Simple Neurohormone Pathway
Catalyzed by a sensory neuron → gland → hormone
Simple Neuroendocrine Pathway
Catalyzed by a sensory neuron → endocrine gland #1 → hormone #1 → endocrine gland #2 → hormone #2
The Master Glands
Control other endocrine glands (hypothalamus, pituitary gland)
Glucagon
Secreted by alpha cells in the pancreas; raise blood glucose levels by converting glycogen to glucose and stimulating the breakdown of fat and protein into glucose
Insulin
Bonds to body cells, telling them to pick up glucose (liver cells store it in chains as glycogen)
Glycogen
Chains of glucose
Local Regulators
Neurotransmitters, cytokines and growth factors, nitric oxide, prostaglandins