Test: Cell-Cell Interactions - 1 - MCAT MCQ

Integrins are cell adhesion molecules that mediate interactions between cells and the extracellular matrix or other cells. In the context of immune cell migration, integrins are crucial for the process of extravasation, which involves immune cells leaving the bloodstream and entering tissues. Integrins on the surface of immune cells interact with adhesion molecules on endothelial cells lining blood vessels, facilitating their migration into tissues.

Gap junctions are specialized channels that directly connect the cytoplasm of adjacent cells. These channels allow for the direct exchange of ions, small molecules, and electrical signals between cells. Gap junctions are found in many tissues and play a critical role in coordinating cellular activities and communication.

G-protein coupled receptors (GPCRs) are a large family of cell surface receptors that play a crucial role in cell signaling. When a ligand binds to the GPCR, it induces a conformational change that allows the receptor to interact with a G-protein. The activated G-protein then initiates intracellular signaling cascades, leading to various cellular responses.

Cadherins are a family of cell adhesion molecules that mediate calcium-dependent cell-cell adhesion. They are responsible for the binding and adhesion of cells to each other, contributing to the formation and maintenance of tissue structure. Cadherins play a crucial role in embryonic development, tissue organization, and cell sorting.

Juxtacrine signaling involves the direct interaction between signaling molecules (ligands) on one cell and receptors on an adjacent cell. This form of cell-cell communication requires close physical contact between the cells involved. Ligands are presented on the surface of one cell and bind to specific receptors on the neighboring cell, initiating intracellular signaling and communication.

Contact-dependent signaling involves direct physical contact between cells, where the signaling molecule on one cell interacts with its receptor on the adjacent cell. The formation of a synapse between a neuron and its target cell is a classic example of contact-dependent signaling, where the presynaptic neuron releases neurotransmitters that bind to receptors on the postsynaptic target cell.

The major histocompatibility complex (MHC) is a group of cell surface proteins that play a critical role in the immune system. MHC molecules are responsible for presenting antigens to T cells, which are key players in the immune response. Antigen presentation by MHC molecules helps activate T cells and initiate immune responses against pathogens or abnormal cells.

Paracrine signaling involves the release of signaling molecules by a cell, which then act on nearby target cells. This form of cell-cell interaction is important in immune responses, as immune cells release cytokines and other signaling molecules that can stimulate or modulate the activities of neighboring immune cells, coordinating the immune response.

Chemotaxis refers to the directed movement of cells in response to chemical signals. In the context of the immune system, white blood cells exhibit chemotaxis during inflammation or infection. They are attracted by chemical signals, such as cytokines or microbial products, which guide them to the site of infection or tissue damage.

Tight junctions are specialized junctions between epithelial cells that form a barrier preventing the passage of substances between cells. They act as a seal and regulate the movement of molecules across epithelial layers, ensuring the selective transport of ions and molecules and maintaining the integrity and function of epithelial tissues.