Cell-Cell Interactions – Learning Objectives

Extracellular matrix

Animal cells secrete materials that form the matrix that provides support and helps to organize the cells. Provides strength, structural support, organization, and cell signaling. The extracellular matrix contains several components.

Cell wall

Provides strength and resistance to compression and expansion. Made of cellulose, contains a primary and secondary wall.

Intercellular attachments

The structure that provides adhesion and communication between cells

Tight junctions

Junctions that form a tight seal between adjacent cells

Middle Lamella

 Glue adjacent plant cell walls together

Hemidesmosomes

Hemidesmosomes connect cells to the extracellular matrix via interins

Gap junctions

Specialized intercellular connections between a multitude of animal cell types.

Plasmodesmata

Passageways between cell walls of adjacent cells in plants that permit direct diffusion of ions and molecules across cytosols of adjacent cells

Provide and explain general reasons why cell signaling is important (sense environmental changes, cell-to-cell communication, etc.)

Cell signaling is significant because it can help regulate the body based on what conditions the body is experiencing. Additionally, cell signaling is critical to get the different parts of the body working together, since they need to communicate.

Direct intercellular signaling

Signals pass through a cell junction from one cell to another

Contact-dependent signaling

Membrane-bound ligand signals bind to receptors on adjacent cells

Autocrine signaling

Cells release signals that affect themselves and nearby target cells

Paracrine signaling

cell releases signals that affect only nearby target cells

Endocrine signaling

Cell releases signals that go through a system to reach cells long-distance

Neuronal signaling

Transmitting electrochemical signals to other cells.

Define “ligand” and “receptor” and compare and contrast receptor/ligand interactions with enzyme/substrate interactions. 

Ligands are the substrate that binds to a receptor. The receptor receives a signal and creates a response. The receptor is the one that changes conformation when bound to a ligand.

Explain how a signal can elicit different effects from different types of cells.

Depending on the pathway and cellular response for each cell, it can cause a different effect.

Receptor Activation/Signal reception

The signaling molecule binds to the receptor of the target cell

Signal transduction

The signal is amplified within the cell

G-protein coupled receptor receptors:

Receptors interact with intracellular G proteins (because they can bind to GTP and GDP), G-Protein converts GDP for GTP.

Ligand-gated ion channels

When signaling molecules bind to this type of receptor, a channel opens and allows the flow of ions into the membrane.

Enzyme-linked receptor signaling

When bound to a ligand, the intracellular domain transforms into a functionally active type. Most operate as protein kinases, which are enzymes that transfer phosphate groups from ATP to specific amino acids in a protein.

Steroid hormone signaling

Receptors are intracellular

Define “second messenger” and list two advantages of having second messenger pathways.

Small molecules or ions relay signals inside the cell after the signal already hits the receptor, Secondary messengers amplify the signal

Define “crosstalk” as it relates to cell signaling and explain the role it plays in generating a cellular response to a set of signals

Crosstalk describes how signals from multiple inputs within a response network can affect a common biological output.

Analyze the ways in which changes in signaling – at different points in the process of signaling – can lead to functional changes for cells.

Changes in signaling that stop signals will reduce the cellular response by the target cell, Example otherwise: When phosphodiesterase is inhibited by caffeine, the cellular response in activated further.