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

The mechanism by which the cell pumps the sodium ions out is called active transport. Active transport requires the

expenditure of energy for the work done by the cell in moving molecules against a concentration gradient. Active

transport enables a cell to maintain a lower concentration of sodium inside the cell, and also enables a cell to

accumulate certain nutrient inside the cell at concentrations much higher than the extracellular concentrations.

The exact mechanism of active transport is not known. It has been proposed that a carrier molecule is involved,

which reacts chemically with the molecule that is to be actively transported. This forms a compound which is

soluble in the lipid portion of the membrane and the carrier compound then moves through the membrane against

the concentration gradient to the other sid

since work must done in transporting the molecule against a diffusion gradient. The energy is supplied in the form of

to move by rotating their flagella.

methyl alcohol are among the by-products of other types of microbial fermentation that are commercially important.

photosynthesis; the main difference is that light drives electrons along an electron transport chain. Bacteria, which

level phosphorylation, as long as there is a sufficient supply of NAD+ to accept electrons during the oxidation step

The carrier molecules are thought to be integral proteins; proteins which span the plasma membrane. These proteins

pyruvate or derivatives of pyruvate. There are many types of fermentation, differing in the waste products formed

Some common words found in the essay are:
ATP H+, Active Transport, NAD+ NADH, Chemiosmosis Populating, CO2 Lactate, electron transport, electron transport chain, transport chain, atp synthase, active transport, lactic acid, h+ gradient, acid fermentation, lactic acid fermentation, alcohol fermentation, electrons electron, oxidative phosphorylation, intermembrane space h+, electrons nadh pyruvate, electrons electron transport,
Approximate Word count = 1304
Approximate Pages = 5 (250 words per page double spaced)