Wednesday, December 18, 2013

Proteins, Classification and Functions of Proteins

Proteins are organic compounds that contain carbon, hydrogen, oxygen, and nitrogen atoms; some proteins also contain sulfur.
Energy from Proteins
      1 gram of protein supplies 4 kcal (the same as CHO).
      Proteins should supply 10-15% of your total daily kcals.

Classification of Proteins

Complete proteins (High-biological-value proteins) contain all of the essential amino acids. Complete proteins are primarily animal proteins, such as those in meats, poultry, fish, dairy products, and eggs.
Incomplete proteins (Low-biological-value proteins) lack one or more of the essential amino acids, usually lysine, methionine, and tryptophan. Most vegetables are incomplete proteins. 

Essential amino acids

      The body cannot make essential amino acids. As a result, they must come from food.
      The nine essential amino acids are: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine

Nonessential amino acids

      "Nonessential" means that our bodies produce an amino acid, even if we don't get it from the food we eat.
      They include: alanine, asparagine, aspartic acid, and glutamic acid.

Functions of Proteins

Growth and replacement: clotting factor production, collagen synthesis, epithelial  cell proliferation, fibroblast proliferation.
Immunity: antibodies, white blood cell production and migration, cell-mediated phagocytosis.
Fluid balance: intracellular osmotic pressure, albumin, maintenance of blood volume
Sodium and potassium balance.
Energy source

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