Protein

Protein

1. FUNCTIONS

   • 1.GROWTH AND MAINTENANCE -Main constituents of cells of body. -Number of cells increases during periods of growth. In tissues always being broken down and must be replaced
   • FORMATION OF ENZYMES- almost all are proteins. Instrumentals in facilitating most of chemical reactions in body. Digestion of nutrients and regulation of energy production in cells
   • TRANSPORT- substances attach to a protein to facilitate transport. E.g. Haemoglobin(protein) carries oxygen. Transport proteins also carry substances across cell membranes
   • HOMEOSTASIS- physiological mechanisms of body, maintain constant internal environment. Hormones acting like messengers carried in circulation. Proteins acting as buffers in circulation maintain acid-base balance

2. SOURCES

   • -Nuts -Vegetables -Eggs -Milk and Cheese-Bread and Cereals -Meat and Fsh
   • NOVEL
     • TVP- Made from Soya Beans - Replace meat -Economical source of HBV -Lower in Iron -Low in Fat -Low in S.Fat
     • QUORN-Used in Veg. Cooking -Lower in Iron - HBV - Low in S.Fat and No cholesterol
     • TOFU- Dried soya beans - High quality protein - B Vitamins -Rich in Calcium (if calcium sulphate coagulant)

3. Dispensable/Indispensable

   • Essential -Indispensable. out of 20, 8 are essential
     • MUST be supplied by diet as they cannot be synthesised
     • Additional 1 must be supplied for infants
   • Non-Essential -Dispensable
     • Can be synthesised by converting 1 AA into another
   • BIOLOGICAL VALUE- % of absorbed protein which is converted into body protein (Used to measure protein)
     • Amount of protein varies in each food. - quality of protein needs to be considered and depends on AA present
     • Indispensable AA- HIGH BV. if it is low in 1 or more essential AA=Low BV
     • AA in shortest supply= Limiting AA

4. PROTEIN COMPLEMENTATION

   • 2 Proteins mixed = higher BV
     • 1 may have surplus of AA-Limiting other AA
   • Pasta and cheese, Beans and Toast, Cereals and milk, Break and Chees

5. DEFICIENCY (PEM covers whole range from protein deficiency to energy deficiency

   • Marasmus (energy deficit)
     • Children -Severely wasted and stunted
       • Occurs in infants under 1, who become severely underweight, weak and lethargic when weaned of breast milk
   • Kwashiorkor (Protein Deficiency)
     • Wasting of muscles, retarded growth, distended abdomen
       • When children weaned onto diet high in starchy foods and low in protein

6. NITROGEN BALANCE

   • Overall indicator of protein matabolism
     • POSITIVE NB=when protein is being retained in the body. -Tissue Synthesis
       • NEGATIVE NB=when there is a net loss of protein from body because protein intake is insufficient
         • Intake=Output, protein is neither being lost or gained