Title: Active Transport Category:Science & Technology Details: Words: 1308 | Pages: 5.6 (approximately 235 words/page)
Active Transport
Active Transport
Since the cell membrane is somewhat permeable to sodium ions, simple diffusion would result in a net movement of
sodium ions into the cell, until the concentrations on the two sides of the membrane became equal. Sodium actually
does diffuse into the cell rather freely, but as fast as it does so, the cell actively pumps it out again, against the
concentration difference.
The mechanism by which the cell pumps the sodium ions out is called active transport. Active transport requires the
expenditure …showed first 85 words of 1308 total…
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…showed last 85 words of 1308 total…important.
Human muscle cells make ATP by lactic acid fermentation when oxygen is scarce. This occurs during the early
stages of strenuous exercise, when sugar catabolism for ATP production outpaces the muscle's supply of oxygen
from the blood. Under these conditions, the cells switch from aerobic respiration to fermentation. The lactate that
accumulates as a waste product may cause muscle fatigue and pain, but it is gradually carried away by the blood to
the liver. Lactate is converted back to pyruvate by the liver cells.
