Excretion and Deamination

Excretion:

removal of the wastes of metabolism from the body​, this is essential before they reach harmful concentrations​

Organs of excretion​

• Liver​- makes urea and processes many substances so they can be excreted​

• Sweat glands​ - Sweat = water and some waste products of metabolism (salts, urea and lactic acid)​

• Kidneys​ - Responsible for maintaining the constant concentration of materials in body fluids and the excretion of nitrogenous wastes​

• Alimentary canal (bile pigments)​ - Feaces is eliminated as it is not a product of metabolism​

• Lungs​ - Carbon dioxide & water

The liver & Protein

Proteins are primarily ‘bodybuilders’ and make up the structural materials of cells​

• If the body has a sufficient supply of carbohydrates and fats, or has stored fat then little protein is used in energy-releasing reactions​

• Excess protein can not be stored in the cell and has to be removed from the body​

• Some protein is broken down in the body but most of this breakdown is incomplete​

• The liver prepares protein for excretion

OTHER FUNCTIONS OF THE LIVER​

• Detoxifies alcohol and many other drugs​

• Deactivates many hormones​

• Breaks down haemoglobin from dead red blood cells to produce bile pigments which are passed out of the body with faeces​

Deamination

The removal of an amino group (NH2) from an amino acid​

• Occurs in liver with help of enzymes​ - Remaining is converted into ammonia (NH3) and carbohydrate.​

• Carbohydrate component used to generate ATP​

• Ammonia however is very TOXIC and soluble in water so it must be converted to a less toxic form – Urea​: circulates the body and is removed by the kidneys and eliminated in urine​

Deamination: equation​  & Urea Equation

Amino acid +     oxygen    —> (enzymes)   carbohydrate + ammonia​

Ammonia + carbon dioxide + energy —> urea + water​

Functions of skin:​

• Physical barrier protecting from the external environment​

• Also has a role in excretion​

Skin’s Role in Excretion:​

• Sweat glands are located in the lower layer of the skin and a duct transports the sweat​

• Even with no visible perspiration, the sweat glands secrete about 500mL of water a day​

• Dissolved in the water are salts, lactic acid and urea