NTR_300_Protein - Fundamentals of Nutrition The Proteins...

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1 Fundamentals of Nutrition The Proteins and Amino Acids NTR-300 Dr. WH Turnbull Unless otherwise stated, all slides and information are derived from: Food Nutrition & Diet Therapy and Krause's Food & Nutrition Therapy, 11th 12th Edns ., 2004 & 2008. By Perspectives in Nutrition, 7th Ed., 2007. By Wardlaw & Hampl, Publ. Mc Graw Hill
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2 Objectives To have a basic knowledge in the chemical composition of protein; protein synthesis and degradation; protein function, digestion, absorption, and metabolism; protein quality, requirements, food sources, and adequacy in the American’s diet; factors affecting protein utilization, protein-energy malnutrition, and vegetarianism. Use of the exchange system will be discussed.
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3 Protein The human body contains 17% protein. 1g protein = 4kcal (16.74 kJ). Composed of carbon, hydrogen, oxygen, and nitrogen. Arranged as amino acids. Working proteins = enzymes, antibodies, transport vehicles, hormones, cellular “pumps,” oxygen carriers. Structural proteins = tendons, ligaments, scars, the cores of bones and teeth, hair filaments, materials of nails.
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4 Amino Acids (AAs) = building blocks of Protein Amino acids in different proteins are found in different combinations and this is what determines the type of protein. About 20 different AAs with 20 different side chains make up most of the proteins in living tissues. Side chain gives identity to the AAs and make them differ in size, shape, and electrical charge.
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6 Essential Amino Acids (EAAs) = AAs that either cannot be made at all by the body or cannot be made in amounts sufficient to meet physiological needs. Essential Amino Acids n = 9 Histidine Isoleucine Leucine Lysine Methionine Phenylalanine Threonine Tryptophan Valine
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7 EAAs - continued EAAs can only be obtained from foods. A non-essential AA. may become an essential AA in special circumstances. For example: tyrosine (a non-essential AA) is made in the body from phenylalanine (EAA). If diet fails to provide enough phenylalanine (as in the medical condition PKU) or cannot convert it to tyrosine, then tyrosine becomes a conditionally essential amino acid.
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8 Semi-essential Amino Acids (conditionally dispensable) Cysteine and Tyrosine are synthesized in the body from Methionine and Phenylalanine (essential AA) respectively. Unless Cysteine and Tyrosine are consumed in the diet they must be made from these essential AAs. Dietary consumption of Cysteine and Tyrosine means that the body can synthesize proteins from them directly freeing up the other AAs for protein synthesis. Therefore Cysteine and Tyrosine are classed as semi essential AAs.
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9 Non-essential Amino Acids (dispensable AAs) Alanine Asparagine Cysteine Glutamine Proline Tyrosine Arginine Aspartic acid Glutamic acid Glycine Serine Non-essential AAs can be synthesized by the body via transamination or deamination.
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NTR_300_Protein - Fundamentals of Nutrition The Proteins...

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