 |  Biology, 6/e Author Dr. George B. Johnson,
Washington University
Author Dr. Peter H. Raven,
Missouri Botanical Gardens & Washington University
Contributor Dr. Susan Singer,
Carleton College
Contributor Dr. Jonathan Losos,
Washington University
Cell-Cell Interactions
Answers to Review Questions| Chapter 7 (p. 140)
1. Receptor proteins on or in a cell determine to which extracellular signals a cell will respond.
2. Paracrine signaling has a short-lived, local effect on neighboring cells. Endocrine signals are secreted into the blood, are comparatively slow to effect a response, and can be very long lasting. Synaptic signaling involves the transmission of a signal over a gap (synapse) between cells for an effect in another nerve or muscle cell.
3. Intracellular receptors can control cell activities enzymatically or through regulation of gene transcription.
4. Chemically gated ion channels typically consist of multi-pass helical protein domains that create "safe passage" through the hydrophobic region of the membrane for an ion.
5. G proteins are intracellular shuttles that relay the message from the membrane signal receptor to other regions in the cell, continuing the cascade of events precipitated by binding to the signal.
6. Binding of the signal to a receptor may result in signal amplification within the cell via multiple protein kinase phosphorylation.
7. Tight junctions function in holding cells tightly together at leak-proof points by a belt of fibrous proteins encircling the cell. Desmosomes "spot-weld" cells together at periodic locations using proteins called cadherins. Adherens junctions involve integrin proteins, which promote the fusion of intracellular matrix proteins with extracellular matrix material, holding cells in specific contact with other structures.
8. Gap junctions are communicating patches between cells formed by connexon proteins which, when aligned, form "pipelines" between adjacent cells. Small molecules (such as certain neurotransmitters) and ions can pass between the openings in the gap junctions.
9. Plasmodesmata are communicating patches of cytoplasm that extend from one cell to another in plants.
|
|
2002 McGraw-Hill Higher Education