Acidosis and Alkalosis, as you know, are usually referring to the acidity or basicity of the blood. When CO2 is produced in cells and diffuses into the blood, the majority of it (~60%) rushes into red blood cells (RBCs) and is changed into bicarbonate ion (HCO3-) and hydogen ion (H+), via carbonic annhydryase. After this reaction, these ions rush back out of the RBCs and travel in the blood/plasma in this form until they reach the lungs. [Regarding the rest of the CO2, 30% of the total makes carbamino compounds in the blood and 10% simply dissolves as blood CO2]
Now, if metabolism is increased, obviously more CO2 will be created and will pump into the blood, creating more HCO3- and H+ ions as a result of carbonic annhydrase. With more H+ in the blood, it naturally becomes more acidic. Normally the body compensates for this by increased respiration to blow off the excess CO2 and rise the pH back to normal. Acidc blood can be created by many things. Let's say someone holds their breath for a while. No CO2 is blown off and hence, their blood becomes acidic. Many pathological states mimic this.
It may also be worth noting that the blood can become alkaline by a number of mechanisms as well. For instance is somebody is hyperventilating, they blow off all of their excess CO2 and the blood becomes basic. Many pathological states also mimic this as well.
Hope this helps.
