If steroid hormones must be bound to protein carriers to travel through the blood, how are they able to bind to intracellular receptors? (The protein carriers cannot diffuse through the membrane.)
What will be an ideal response?
Answer: Steroid hormones are bound reversibly to their protein carriers, and they are soluble in low concentrations in the blood. When the steroid hormones are produced, there is such a high concentration released that they bind to the protein carriers. For the typical steroid hormone, the majority binds to the protein carrier but a small amount remains unbound. When the blood passes by the target cell, the free steroid hormone diffuses into the cell to bind to the receptor. This creates an area of decreased concentration of the hormone, so a small amount releases from the carrier protein is dissolved.
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A) origin. B) aponeurosis. C) insertion. D) tendon. E) lever.
When a neuron is in the resting state, ________
A) Na+ leaks out of the cell and K+ leaks into the cell B) both Na+ and K+ leak out of the cell C) both Na+ and K+ leak into the cell D) Na+ leaks into the cell and K+ leaks out of cell
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Which accurately describes the handling of urea by the kidney?
A. None of the urea that reaches the kidney is excreted in the urine. B. About half of the urea that is filtered is excreted in the urine. C. All of the urea that reaches the kidney is excreted in the urine.