Cell Communication and Signaling

Communication in Yeast

To mate, 2 sexes fuse and become diploid cell

Bind to specific receptors on cells of “opposite” sex

Local Communication

Paracrine

Synaptic

Direct Contact

Long Distance Communication

Endocrine/hormonal signaling

Paracrine Signaling

Cell releases signaling molecules to fluid around it and nearby cells receive signal

Synaptic Signaling

Used by nerve cell, fast and specific with signals released into synapse

Direct Contact Signaling

Communicate through physical contact (cell-cell recognition)

eg. gap junctions and plasmodesmata

Endocrine Signaling

Hormones travel through bloodstream to distant cells

Only cells with correct receptors will respond

3 Stages of Cell Signaling

Reception

Transduction

Response

Receptor

Signal molecule (ligand) binds to receptor

Transduction

Binding changes the receptor→sequence of biochemical events (signal transduction pathway)

Response

Cell responds to information that is transduced

Epinephrine Signaling

Epinephrine binds receptors

Signal pathway activate enzymes

Glycogen breaks down into glucose

Energy available

Types of Receptors

G protein-linked

Enzymes

Ligand-gated ion channels

Internal

G protein-linked receptor

Common receptors

Binding causes activation of G protein and GDP replaced with GTP

G activates enzyme, cell response occurs

GTP hydrolyzed→signal stops

Enzyme Receptors (Tyrosine Kinase)

Are enzymes themselves

Initiates phosphorylation, comes from ATP

Ligand-gated ion channel

Ligand binds, channel opens, ion flows through

Changes in ion concentration triggers cellular responses

Internal Receptors

Usually hydrophobic signals enter cell directly through membrane

Changes gene expression from receptor entering nucleus