Proteins Flashcards
What are four functions of Protein?
• blood clotting - several proteins found in plasma play an essential role in blood clotting, including thrombin and fibrogen.
• growth, maintenance and repair functions - proteins are the main consistents of the cells in the body. The membrane surrounding the cells contains proteins which is also found within the cell. At all times protein is constantly being broken down and must be replaces by the amino acids supplied in the diet. This replacement of tissue occurs in all people at all stage of life but number of cells increase during periods of growth: childhood, adolescence and pregnany.
• protein as a source of energy, not all protein is used for growth and repair so the amount of protein supplied in this way depends on biological value. The diet may supply more protein than what is needed so this is used for energy. Amino acids (proteins) not required for protein synthesis are deaminated in the liver i.e nitrogen containing parts of amino acids, are removed in urea. urea is a waste product so it is carried to the blood to the kidneys where it is excreted un the urine. The Deaminated molecule contains carbon , oxygen and hydrogen. They enter chain of reactions where glucose is oxidised in cells to supply energy.
• transport - many substances that need carried around body from digestive system or stores of sites of actions cannot travel in blood aline (they are insoluble or harmful) when attached to proteins transport is facilitated. Haemoglobin is a transporting protein which carries oxygen in the body.
Explain the difference between dispensible and indispensable amino acids.
Dispensable amino acids can be synthesised in the body by converting one amino acid into another within body cells. Indispensable amino acids must be supplied by protein in the diet as they cannot be synthesised by the body.
Define the term biological value
Biological value of a protein is used as a measure of protein quality.
