Functions of Proteins

Functions of Proteins

1. build & repair

2. regulating body functions

   a. metabolism

   b. digestion

   c. fluid & electrolyte balance

   d. development of antibodies

3. providing energy each gram of protein provides 4 calories

Digestion and Absorption

1. Mechanical digestion

   a. mouth

   b. grind break up

2. Chemical digestion

   a. stomach HCL prepares stomach

   b. enzyme pepsin reduces protein to polypeptide

   c. polypeptide is 10+ amino acids bonded together

   d. in small intestine, three pancreatic enzymes: trypsin, chymotrypsin, & carboxypeptidase aids

   absorption through villi

Metabolism & Elimination

1. amino acids are broken down

2. nitrogen-containing amine group is stripped off "deamination" →ammonia produced

3. liver picks up ammonia convert to urea

4. kidneys filter urea

5. remaining parts are used for energy or converted to CHO or fats & stored as glycogen or adipose

   tissue

Dietary Requirements

1. determined by size, age, sex, physical, & emotional condition

2. the National Research Council of the National Academy of Sciences considers the average daily

   requirement is 0.8 grams protein for each kg body weight

Protein Excess

1. saturated fats and cholesterol found in complete protein contribute to heart disease

2. connection to colon cancer

3. substitute meat for vegetable or fruit

4. increased demand on kidney & liver

5. National Research Council recommends that protein intake represent no more than 15-20% of one's daily caloric intake. (should not exceed double the amount in table of daily recommended allowances)

Nitrogen Balance: nitrogen intake = nitrogen excreted