BIO130 - Exam 2 - Lecture 5

Ligand

released from “signaling cells”

bind to “receptor proteins” on “target cells”

Autocrine

ligand binds to receptor on the signaling cell

Direct Signaling

Ligand travels from cytoplasm to cytoplasm from signaling cell to target cell

Paracrine

ligands bind to receptors on nearby cells

rapidly degraded ligand ensures signal is local

Endocrine Signaling

ligands bind to receptors on distant cells

Intracellular Receptor

receptor protein in cytoplasm of cell

ligands for these receptors must be small + hydrophobic

Cell Surface Receptor

Receptor protein is on surface of cell

Anchored in plasma membrane

Ligands are water soluble

extracellular, transmembrane, and cytoplasmic domains

Signal Transduction

Binding of ligand leads to change in shape or receptor

ie. creation of second messenger, phosphorylate proteins

Phosphorylation

modification of a protein by the addition of a phosphate group(s) from ATP

catalyzed by a class of enzymes called “kinases”

De-phosphorylation

removal of a phosphate group(s) from a protein

catalyzed by a class of enzymes called “phosphatases”

Single-celled yeasts

secrete a “mating factor” ligand to find other yeast cells to mate withB

Bacteria Communication

Quorum sensing

Some bacteria can form biofilms, but requires high cell density

Biofilms

matrix of proteins and sugars that protects colonies

Apoptosis

Programmed cell death to protect surrounding cells