Proteins Chapter 6 BIOL1400 Dr. Mohamad H. Termos

Proteins - Contain Nitrogen which carbohydrates and fats do not - Regulate and maintain our bodies - Provide 4 kcals per gram

Amino acids - Building blocks of protein - Basic structure - Determination of specific amino acids a. Nonessential amino acids b. Essential amino acids 1) Health implications if essential needs are not met

Dietary considerations - Animal proteins provide all essential amino acids 1) Support body growth and maintenance 2) High quality; complete - Plant proteins lack one or more amino acids 1) Lower quality; incomplete - Partially complete proteins support maintenance only; have a limiting amino acid - Combining proteins to make them complete 1) Complementary proteins

Protein in foods Plant proteins - Nutrient density - Food sources a. Soy b. Legumes c. Beans - Side effects

Protein digestion - Begins in the stomach 1) Acting enzymes are pepsin and gastrin 2) Stomach acid (HCl) is important in pepsin activation - Small intestine 1) Enzymes released in response to partially digested proteins 2) Proteins divided into shorter amino acid chains

Absorption - Short amino acid chains are absorbed - Final digestion of amino acid chains into amino acids occurs in absorptive cells of the small intestine - Amino acids travel to the liver via the portal vein 1) Combined into protein 2) Converted to glucose 3) Converted to fat 4) Released into blood stream

Putting proteins to work in the body - Produce vital body structures - Maintain fluid balance Contribute to acid-base balance - Form hormones and enzymes - Contribute to the immune function and production of antibodies - Form glucose - Provide energy

Protein needs - Sufficient amount needed to balance output with intake - Requirements determined by nitrogen balance - Estimated requirements a. Adults: 0.8 grams per kilogram body weight b. Doubles during infancy c. Pregnancy increases protein needs by about 10 to 15 grams per day d. Endurance athletes and body builders: 1.2-1.4 grams per kilogram body weight

Protein-energy malnutrition Kwashiorkor 1. Primarily protein deficiency 2. Associated with weaning from breast to starchy diet 3. Energy needs marginally met and protein intake inadequate 4. Symptoms a. Apathy, listlessness b. Failure to grow and gain weight c. Increased susceptibility to infection d. Reduced muscle mass, abdomen and leg edema e. Changes in hair color, flaky skin 5. Disease process can reverse with adequate diet

Protein-energy malnutrition Marasmus 1. Primarily from insufficient amount of protein, energy, and other nutrients 2. Due to no breast feeding or early weaning 3. Seen in cities where fashionable to bottle-feed, poor sanitation 4. Symptoms a. "Skin and bones" appearance b. Little or no subcutaneous fat 5. Full recovery from the disease may never occur a. Brain may not grow to its full adult size