A concentration gradient ceases to exist when

a. all molecules have moved from low
concentration to high concentration.
b. the membrane pores close.
c. the temperature drops.
d. there is equilibrium between the two sides
of a membrane.
e. bulk flow intervenes.


D

Biology & Microbiology

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What happens when a resting neuron's membrane depolarizes?

A) There is a net diffusion of Na+ out of the cell. B) The equilibrium potential for K+ (EK) becomes more positive. C) The neuron's membrane voltage becomes more positive. D) The neuron is less likely to generate an action potential. E) The cell's inside is more negative than the outside.

Biology & Microbiology

Animal cells can survive only within a temperature range from about:

1.-2°C to 45°C (28°F to 113°F)
2.0°C to 40°C (32°F to 104°F)
3.0°C to 45°C (32°F to 113°F)
4.0°C to 48°C (32°F to 118°F)

Biology & Microbiology

Nitrogen has a higher electronegativity than hydrogen.  As a result you would expect that ammonia (NH3) molecules can form ________ with each other.

A. hydrophilic bonds B. hydrogen bonds C. ionic bonds D. covalent bonds E. cohesive bonds

Biology & Microbiology

Punctuated equilibrium proposed by Eldredge and Gould in 1972 is an evolutionary process that involves

A. gradual change observable in the fossil record with very little, if any, stasis. B. gradual change observable in the fossil record followed by periods of no change at all. C. "spurts" of change observable in the fossil record with very little if any stasis. D. gradual change observable in the fossil record followed by periods of stasis. E. "spurts" of change observable in the fossil record followed by periods of stasis.

Biology & Microbiology