Some cells such as human nerve cells and muscle cells contain many more mitochondria than do other cells, such as skin cells. Why do some cells have more mitochondria than others?

A) The cells use more energy
B) The cells divide frequently
C) The cells break down more proteins
D) The cells store more nutrients

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).

How does secondary succession differ from primary succession?

Which best describes a benefit of using dna technology in medicine? a) medicine can be produced in mass quantities. b) medicine can be distributed at a reduced cost. c) medicines have fewer side effects. d) medicines are resistant to antibiotics.