Diffusion and respiration GapFill

Respiration is the process used by organisms to generate energy for movement and all  nucleicnervouselectricalmetabolic reactions. Because it is  an exothermican anabolican endothermican endogenous reaction, respiration is also important for keeping organisms warm.

When there is  oxygenglucosemethanewater available, aerobic respiration converts oxygen and  ethanolnitratecarbon monoxideglucose to carbon dioxide and water, but if it is lacking,  hypoaerobichyperaerobicanaerobiclactoaerobic respiration in muscles converts glucose to lactic acid, which can cause a painful or burning sensation. This yields less energy than aerobic respiration because of the incomplete oxidation of glucose, and the lactic acid produced must eventually be converted back to glucose by the  small intestinethyroid glandpancreasliver.

 FiltrationActive transportSelective reabsorptionDiffusion is the passive movement of substances from an area of higher concentration to an area of lower concentration. Examples of this in nature are the movement of the waste product  glucoseureacarbon monoxidebile from the liver cells into the blood (where it is transported to the kidneys) and the movement of  antibodieswaterureaplasma and dissolved mineral ions from the soil into plant roots.

This process can be sped up by several factors, including increasing the concentration gradient, increasing the  pHtemperaturevolumefriction or increasing the surface area of the membrane. Having a  variablelargeconstantsmall surface-area-to-volume ratio allows this process to occur rapidly, which allows single-celled organisms to exist without complex transport systems, and is also one reason why alveoli are efficient at gas exchange.

A cube-shaped cell with sides measuring 3 µm has a surface area of  60365418 µm² and a volume of  274272918 µm³. The surface-area-to-volume ratio is  4 : 32 : 13 : 12 : 3.