NUTR 225 Ch. 6
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- 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
Amino acids, Two types?
- 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.
Four levels of protein structure
- 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
Complementary food combinations
- 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
Digestion of Proteins
- - 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
Functions of Proteins
- - Cell growth/repair/maintenance
- - Enzymes
- - Hormones
- - Fluid and electrolyte balance
- - pH balance
- - Antibodies
- - Energy source
How much protein should we eat?
- - Sedentary adults require 0.8g/kg of body weight (10-35% protein/kg)
- - Children, adolescents, pregnant/lactating women, athletes, vegetarians require more
Risk of too much protein
- - High cholesterol and heart disease
- - Possible bone loss
- - Kidney disease
Diet of plant origin
Different types of vegetarianism
- 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.
Protein-energy malnutrition, Two types?
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
Genetic diseases = protein abnormalities
- - Phenylketonuria
- - Sickle cell anemia
- - Cystic fibrosis
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