carbon dioxide from the air is used to produce glucose and other  compounds.
Blood Filtration in the Kidney. The kidneys filter about one-quarter (750-1000 pints) of the blood that is output by the heart daily. This blood is sent to the body's filter treatment plant, where it is purified by the kidneys and circulated on to the rest of the body. Some of the blood flow becomes fluid waste (1/1000th to 2/1000th) and is sent into the bladder for storage until it can be conveniently expelled. This toxic waste is called urine.
A major part of this cleaning of the  blood takes place in the kidneys and, in particular, in the  nephrons, where the blood is filtered to produce the urine. Both  kidneys in the body carry out this essential blood cleansing  function.hereas reabsorption  moves substances out of the tubules and into the blood, secretion  moves substances out of the blood and into the tubules where they  mix with the water and other wastes and are converted into urine.