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Protein

Protein. Nitrogen Cycle. Plants use N2 to make a.a’s and proteins Animals eat plants Humans consume plants and animals Decomposed organic matter puts N2 back into soil to be use by plants. Protein. Structure Building block of all proteins is the amino acid

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Protein

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  1. Protein

  2. Nitrogen Cycle • Plants use N2 to make a.a’s and proteins • Animals eat plants • Humans consume plants and animals • Decomposed organic matter puts N2 back into soil to be use by plants

  3. Protein Structure Building block of all proteins is the amino acid Contains carbon, hydrogen, oxygen, nitrogen Polypeptides made of 100-300 aa’s Eg leucine, alanine, serine etc

  4. Protein synthesis • Amino acids join with a peptide bond • Peptide bond formed between • Carboxyl OH group of 1st amino acid • Nitrogen group of 2nd amino acid • Polypeptide • Protein unit that contains many peptide bonds

  5. Amino acids • 9 essential amino acids • 11 non-essential a.a. • Long chains of amino acids make up different proteins • Potential for endless combinations of amino acids

  6. Non-essential a.a. • Can be made in the body from essential a.a. or from other non-essential amino acids or be supplied by body proteins • Most foods except fruit, vegetables and fats contain protein • Non-animal products are a significant source of protein

  7. Essential amino acids • The body cannot synthesise these from other amino acids • Must be provided in the diet or own body proteins will be used • Meat, poultry, fish, eggs, dairy products and soya beans

  8. Functions of PROTEIN • Growth, maintenance and repair of all body cells • Replacement • Fluid balance • Acid base balance • antibodies • Hormones • Transport proteins • enzymes • Source of energy

  9. Examples of body proteins • Collagen and elastin = skin • Keratin = hair • Albumin = blood • Hemoglobin = red blood cells • Insulin = hormone • Lipase, protease = enzymes • DNA and RNA = genetic material

  10. Digestion, absorption and use • Peptide chain “straightened” to allow access for enzymes • Broken down to single a.a. • Transported via blood to cells • Held in a.a. pool for up to eight hours • Converted to fat unless used for cell repair or energy

  11. Protein Quality • Animal protein • Wine, vinegar, salt, acid, heat denatures proteins, loosening bonds making it more tender • Denaturing proteins makes them more available to digestive enzymes for absorption • Vegetable Protein • Less well digested • Encased cell walls thus need to be cooked • Contain enzymes that interfere with protein digestion

  12. Reference Protein • Eggs • Most complete and digestible protein • Used as a standard for measuring protein quality • Protein Quality • BV (Biological Value) • BV= amount of protein nitrogen that is retained for growth and maintenance

  13. Health effects of protein • Protein Deficiency • Poor growth in children • Weight loss and wasting in adults • Two conditions • Marasmus • Kwashiorkor

  14. Risks with high protein intake • Excess energy intake • May limit CHO intake • Increased need for water • Calcium losses • ? Stress on the kidneys

  15. RDIs Men 19-64 yrs 55g/day Women 19-54 yrs 45g/day Protein intake in NZ 15 yrs plus 105g/day 15% of energy 15yrs plus 71g/day 16% of energy RDI and Intakes

  16. Estimating protein needs To maintain protein balance in the body, the best estimate of protein required for nearly all adults is 0.8g/kg body weight When might the body be in positive balance ? When might the body be in negative balance ?

  17. Food sources of protein • Animal – meats (beef, chicken, fish etc), eggs, milk and milk products • Vegetable – legumes (dried beans, peas and lentils), nuts, seeds, grains eg rice, corn etc • NZ Diet -beef and veal 14%, bread 11%, milk 10%, poultry 7%, seafood 7%.

  18. Vegetarian diets • Vegetarian diets with no animal products can supply all the essential amino acids • Most vegetable proteins are only short of one a.a. = the limiting a.a. • The limiting a.a. can be supplied by another vegetable protein • Knowledge of food combinations important

  19. Example Wheat is low in lysine but served with dried beans, rich in lysine (limiting in methionine) can provide the correct balance of all essential aa’s.

  20. Protein content of food 1 Bagel 6 grams 4 fish fingers 9 1 cup Muesli 15 1 meat pie 13 1 cup porridge 4 1 cup hot chips 9.5 1 cup Soya milk 8 1 sausage roll 10 1 cup pasta 4.5 100 g gurnard 26.5 1 cup brown rice 5.5 100 g tuna 23 100 g cheese 25 100 g fillet steak 27 100 g cottage cheese 15 100 g chicken breast 25 1 cup ice cream 6 100 g lamb 26 1 cup milk 8.5-11 100 g turkey breast 29 1 pot yoghurt 7 100 g luncheon 11 1 hamburger 15 100 g mussels 23 1 Big Mac 27 100 g peanut butter 29 1 cup coleslaw 4 1 Mars bar 3.2 100 g cauliflower 2 1 cup lentils 10

  21. Practical advice • Protein should be provided by wide range of available foods, including lean meat, chicken and seafood, eggs and milk. Bread is also important source. Include some vegetable sources too. • Choose low fat options of meat and milk products. • If vegetarian, choose protein from diverse plant sources (legumes, nuts, breads, cereals etc.) If lacto-ovo vegetarian, include eggs and milk products.

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