The surface area/volume ratio is an important factor for one celled organisms. all the parts of a cell go into making its volume: the nucleus, the vacuoles, the lysosomes, cytoplasm, etc. however, the outer surface of any cell is the

The right answer is cell membrane.

The cell membrane consists of a double layer of phospholipids in which many molecules are inserted. (proteins, glycoproteins, glycophospholipids ...).

This membrane is "dynamic" and renews itself constantly. Its thickness is 7.5 nm.

The cell membrane separates the interior of the cell from the extracellular medium while maintaining communications and exchanges therewith.

the answer is tropical areas. the tropical areas obtain more

radiant energy from the sun than they lose to space through terrestrial

radiation, and vice versa for polar areas. earth has an energy remaining in the

tropics and an energy scarcity for the polar areas.

explanation:

before, trains worked using the steam engine. thus, it uses heat so it is crucial to apply heat balance. the steam engine absorbs energy during the stage of boiling water. so, this is the endothermic reaction. when the steam is used to work the piston, it has to release this energy through running the train. the excess energy is released as an exhaust to the chimney. this is the exothermic process because it releases energy to the surroundings.