AP Bio - Unit 4: Cell Communication

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