Excretion: Removal from the body of toxicmetabolic waste products (main metabolic waste products: CO_2 from decarboxylation reactions in respiration and nitrogen-containing products e.g. ammonia, uric acid, creatine and urea)
Organs involved: Lungs (remove CO_2), liver (detoxify ingested toxins; produce urea from excess amino acids), and kidney (filter urea from blood plasma and form urine with high concentration of urea)
Excess CO_2 in blood plasma can cause respiratoryacidosis (acid blood), in plasma it combines with water to form carbonicacid which dissociates to form hydrogen and hydrogencarbonate ions; hydrogen ions lower blood plasma pH
- if pH drops below 7.35, respiratoryacidosis occurs with slowed breathing, drowsiness, headache and confusion
Increased CO_2 reduces haemoglobins’ oxygen affinity; reacts with water to form hydrogen carbonate and hydrogen ions (catalysed by carbonic anhydrase) and hydrogen competes with oxygen for binding space
Excess amino acids cannot be stored in the body; amino group are removed from each and initially form ammonia (very toxic and soluble in body fluids, forming alkaline solution; increases pH, changes proteinstertiary structure - e.g. enzymes) - it is rapidly converted into urea in the liver; still toxic, but less so as is less soluble
