Essential Knowledge 3.D.2

Cells communicate with each other through direct contact with other cells or from a distance via chemical signaling.

Cells communicate by cell-to-cell contact. Examples include:

• Immune cells interact by cell-cell contact, antigen-presenting cells (APCs), helper T-cells and killer T-cells. [See also 2.D.4]
• Plasmodesmata between plant cells that allow material to be transported from cell to cell.

Cells communicate over short distances by using local regulators that target cells in the vicinity of the emitting cell. Examples include:

• Neurotransmitters
• Plant immune response
• Quorum sensing in bacteria
• Morphogens in embryonic development

Signals released by one cell type can travel long distances to target cells of another cell type. Endocrine signals are produced by endocrine cells that release signaling molecules, which are specific and can travel long distances through the blood to reach all parts of the body. Examples include:

• Insulin
• Human growth hormone
• Thyroid hormones
• Testosterone
• Estrogen

NOTE: No specific system, with the exception of the endocrine system, is required for teaching the concepts in 3.D.2 . Teachers are free to choose a system that best fosters student understanding. Study of the nervous and immune systems is required for concepts detailed in 3.E.2 and 2.D.4.

Students should be able to:

LO 3.34 Construct explanations of cell communication through cell-to-cell direct contact or through chemical signaling.

LO 3.35 Create representation(s) that depict how cell-to-cell communication occurs by direct contact or from a distance through chemical signaling.