Concept explainers
Vicious Venoms
Most snake venoms are nasty cocktails of toxins. In addition to breaking down phospholipids, some rattlesnake venoms contain toxins that bind to and inhibit the activity of receptor proteins for acetylcholine. Inhibiting the action of acetylcholine on heart muscle cells increases heart rate, which speeds the travel of venom through the body. Krait snakes, native to Asia, produce a venom protein that binds to the direct-acting membrane channel receptors for acetylcholine, including those on skeletal muscle cells. Once bound, the protein remains firmly attached, blocking acetylcholine from binding. This prevents muscles from contracting: an untreated krait bite victim often dies when the skeletal muscles that control breathing are paralyzed.
The ability of substances to move across membranes is crucial not only to controlling heart rate and breathing, but also to all other aspects of staying alive. How do proteins control the movement of substances across membranes?
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Biology: Life on Earth with Physiology (11th Edition)
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