NUTR 225 Ch. 6

• large complex molecules composed of amino acids
• - carbon, hydrogen, oxygen, nitrogen
• - primary source of nitrogen in diet
• - 20 diff. amino acids used to make proteins

- Essential amino acids: cannot be produced by our bodies; must be obtained from food, 9 of 20 are essential.

-Nonessential amino acids: Can be made by our bodies

• Use of the genetic information in DNA to make RNA.
• - mRNA copies the genetic info and carries it to ribosome

Conversion of genetic info in RNA to assemble amino acids in the proper sequence to synthesis  a protein on the ribosome.

• 1) Primary structure: sequential order of amino acids
• 2) Secondary structure: spiral shape due to chemical bonding between the amino acids
• 3) Tertiary and quaternary structure: further folding into a unique 3D shape that may be globular or fibrous

• - Protein loses shape due to heat, acids/bases, heavy metals, or alcohol
• - It's irreversible!

• Does not contain all essential amino acids in sufficient quantities.
• - growth and health are compromised
• - "low quality" protein

• contains sufficient amounts of all nine essential amino acids
• - "high quality" protein

Combining two incomplete proteins to make a complete protein

• Two protein sources that together supply all nine essential amino acids
• e.g.: beans and rice

• 1) Legumes + Grains/Nuts and Seeds: Rice and lentils
• 2) Grains + Legumes: Peanut Butter and Bread
• 3) Vegetables + Legumes: Tofu and Broccoli
• 4) Nuts and Seeds + Legumes: Sesame seeds w/ mixed bean salad

• - Mouth-> Proteins in food are crushed and moistened by saliva
• - Stomach-> HCl denatures proteins; Pepsin breaks down protein into single amino acids/polypeptides
• - Small intestine-> Proteases secrete to digest polypeptides; cells in the wall of small intestine completely breakdown polypeptides into single amino acids
• - Liver-> Amino acids are transported to liver

• - Cell growth/repair/maintenance
• - Enzymes
• - Hormones
• - Fluid and electrolyte balance
• - pH balance
• - Antibodies
• - Energy source

• - Sedentary adults require 0.8g/kg of body weight (10-35% protein/kg)
• - Children, adolescents, pregnant/lactating women, athletes, vegetarians require more

• - High cholesterol and heart disease
• - Possible bone loss
• - Kidney disease

Diet of plant origin

• 1) Semivegitarian: exclude or limit red meat
• 2) Pescovegetarian: fish as only source of protein
• 3) lacto-ovo-vegetarian: exclude animal flesh and seafood
• 4) lactovegetarian: milk and cheese for animal source of protein
• 5) ovovegetarian: excludes dairy, flesh, seafood
• 6) vegan: not provide adequate B12, zinc, iron, or calcium
• 7) Macrobiotic: can cause malnutrition and death
• 8) Fruitarian: deficient in protein, calcium, zinc, iron, vitamin B12, riboflavin, etc.

Disorder caused by inadequate intake of protein and energy

• 1) Marasmus: disease resulting from severely inadequate intakes of protein, energy, etc...
• symptoms: wasting of muscle tissue, stunted growth, stunted brain development, anemia

• 2) Kwashiorkor: disease resulting from extremely low protein intake
• symptoms: weight loss and muscle wasting, edema resulting in distention of belly, retarded growth and development

• - Phenylketonuria
• - Sickle cell anemia
• - Cystic fibrosis