Cell Communication and Signal Transduction

Cell communication

Responsible for the growth and development of multicellular organisms - critical for cell function and survival

Three Cell Communications

1. Direct Contact

2. Local Signaling

3. Long-distance signaling

Direct contact

Communication through cell junctions since signaling substances and other material dissolved in the cytoplasm can pass freely between adjacent cells

Animal cell junctions

gap junctions

Plant cell junctions

Plasmodesmata

Examples of Direct Contact

Immune Cells - antigen presenting cells (APCs) communicate to T cells through direct contact

Local regulators

A secreting cell will release chemical messages (local regulators/ligands) that travel a short distance through the extracellular fluid

Chemical messages in local regulators

Chemical messages cause a response in a target cell

Examples of local regulators

Paracrine and Synaptic signaling

Paracrine signaling

secretory cells release local regulators (growth factors) via exocytosis to an adjacent cell

Synaptic signaling

Occurs in animal nervous systems when neurons secrete neurotransmitters to diffuse across the synaptic cleft

Synaptic cleft

Space between the nerve cell and target cell

Long distance signaling

Animals and plants use hormones for this

Long distance signaling in plants

Release hormones that travel in the plant vascular tissue or through the air to reach target tissues

Long distance signaling in animals

Use endocrine signaling

Endocrine signaling

Specialized cells release hormones into the circulatory system where they reach target cells

Example of long distance signaling

Insulin - released by pancreas into the bloodstream where it circulates through the body and binds to target cells