Sounds are produced by the of an object or a column of air.

The kidney filters potentially toxic substances in the blood, and thus “clears” the blood of those substances. this clearance function is dependent upon and proportional to the diffusion gradient of the substance across filtering capillaries, i.e. if the concentration of the substance is doubled, twice as much will be cleared from each ml of blood that is filtered. suppose that the body produces a constant amount of a substance x per unit of time. the kidneys eliminate substance x at a rate directly proportional to the concentration of the substance and the volume of blood cleared each minute (c): elimination = c × [x], where [x] is the steady-state concentration of substance x. imagine an individual with an initial concentration of x equal to [x]0 who develops kidney disease. her baseline clearance c0 drops to one half of the original (½c0). what is the new steady state concentration of x? (for simplicity, assume that substance x is 100% filtered by the kidney).

Ras is a g-protein that is activated when a growth factor attaches to egfr. its activation results in the replacement of a gdp molecule with a gtp molecule, thus allowing a signal transduction pathway to be activated. considering the signal pathway illustrated on this page, what is one potential outcome of a mutation in the ras gene that leads to ras protein hyperactivity. be specific.

Substances that can pass through cell membranes by diffusion include a. na ions. b. proteins c. glucose. d. oxygen.