NDFS 200 exam 2

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    Generic Amino Acid 
  2. Acidic Amino Acids
    At neutral pH, lose proton ( --COO−  ), negatively charged
  3. Basic Amino Acids
    At neutral pH, gain a proton (-NH3+), positively charged
  4. Histidine:
    contains imidazole group (aromatic ring) that can be positively charged
  5. Branched
    chain protein
    essential body can't produce, consumed by muscle 
  6. Essential amino acids
    PVT TIM HA*LLAny Help In Learning These Little Molecules Proves Truly Valuable.

    • Histidine
    • Isoleucine
    • Leucine
    • Lysine
    • Methionine
    • phenylaline
    • threonine
    • tryptophan
    • valine
    • phenylalnine
    • valine
    • threomine
    • tryptophan
    • Arginine (in some birds)
    • Leucine
    • Lysine
  8. ¨Primary proteins
    ¤AAsequence, peptide bonds

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  9. ¨Secondary proteins
    • hydrogenbonds between backbone atoms
    • α-helix or β-sheets

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  10. Tertiary proteins
    5 types of bonds between R groups

    H bonds

    Ionic attraction



    Disulfide bonds

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  11. ¨Quaternary:
    ¨Quaternary: subunit association

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  12. ¨Denatured dietary proteins are:
    safer (non-functioning enzymes,non-virulent bacteria, viruses)less allergenic¤more digestible, increase exposure toenzymes
  13. nonessenntal amino acids
    • Alanine
    • Arginine
    • Asparatic acid
    • cysteine
    • Glutamine
    • Glycine
    • proline
    • serine
    • tyrosine
  14. Essential amino acids
    • Histidine
    • Isoleucine
    • Leucine
    • Lysine
    • Methionine
    • phenylaline
    • threonine
    • tryptophan
    • valine
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    Aspartic acid
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    Glutamic acid
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  33. Peptide Bond Formation
    • Covalent bond
    • NH2 reacts w/-COOH

    H20 as by-product

    • AA side chain determines protein folding
    • --> myriad of functions
  34. All or none
    • Histidine deficiency à found in dipeptides in carnosine
    • & anserine – very high concentrations in human skeletal muscle & can be degraded to  get histidine; degrated Hgb (a histidine-rich protein) may allow body to maintain supply of histidine if deficient in diet.
  35. ¨High quality (complete) protein
    • provides 9 Essential AAs in proportion for human
    • use

    usually from animal sources
  36. ¨Low quality (incomplete) protein
    ¤EAAs pattern does not match human requirement

    ¤typically from plant sources

    ¤one or more EAAs low or missing (e.g. corn low in tryptophan and lysine)
  37. ¨Biological Value (BV)
    Ratio of N retained to N absorbed

    N retained

    N absorbed

    • Measures how efficiently the absorbed
    • food protein can be turned into body tissue
  38. ¨Protein Efficiency Ratio (PER) 
    • FDA uses for labeling regulations for
    • infant food

    • Compares the weight gained in a growing
    • rat after 10 days or more eating a standard amount of a specific protein source

    (g weight gain/g protein consumed)
  39. ¨Chemical Score
    • ¤EAA
    • in the food divided by an “ideal” amount for that essential AA

    • ¤The
    • lowest EAA score is the C.S. for that food
  40. ¨Protein Digestibility Corrected Amino Acid Score
    PDCAAS = Chem. Score x digestibility (generally between 0.9-1.0)

    Maximum value is 1.0 (= milk, eggs, soy protein)

    Nutrition Facts panel rarely lists % DV for protein, since manufacturers don’t calculate PDCAAS
  41. Net Protein Utilization
    Ratio of AA converted to protein to AA supplied

    AA converted to protein

    AA supplied
  42. Protein Complementation
    Combine foods with different amino acid patterns to supply EAAs in proper proportion

    e.g. grain (low in lysine) + bean (low in methionine) = complete protein
  43. Functions of protein in the body
    5-10% of energy used in body (expensive energy)

    Prolonged exercise (↑ 10-15% -- branched chain AA in muscle – Leucine, Isoleucine, Valine)

    If there are insufficient total kcalories, then dietary (and body) protein is used for energy
  44. Functions of protein in the body
    ¨Glucose formation
    • Gluconeogenesis for brain and RBC between meals and low
    • CHO diets
  45. Functions of protein in the body
    Acid-base balance
    Regulation of pH by buffering resulting from charged amino acid side chains
  46. Functions of protein in the body
    Connective tissue, bone matrix, epidermal cell walls (skin), lipoproteins, antibodies, etc.

    Collagen, actin and myosin, plus hemoglobin make up 50% of the protein in the body
  47. Functions of protein in the body
    Immune function
    Antibodies & immune cells require protein 
  48. Functions of protein in the body
    Protein hormones and enzymes
    Insulin, pituitary hormones, thyroid hormone

    Enzymes for thousands of metabolic reactions
  49. Protein RDA
    100 kg x 0.8 g/kg/day = 80 g/day

    ¨To gain 2 lb (0.91 kg) muscle/week

    Muscle is 22% protein.

    0.22 x 0.91 kg/wk = 200 g/wk = 29 g/day
  50. Transamination
    Process for synthesizing nonessential amino acids.

    Carbon skeleton” from a metabolic cycle accepts amino group to become amino acid

    Available for protein synthesis
  51. Amino Acid “Sparing” 
    ¨Humans do not synthesize cysteine or tyrosine from scratch.

    ¨Why are they not essential?

    Cys is made from Met, and “spares” need for some Met when in the diet.

    Tyr is made from Phe.
  52. ¨If transamination did not occur, what
    would be the result?
    1.Every amino acid would be essential.
  53. Excess protein (NAS)
    • ¨45% kcal from protein – weakness, nausea,
    • diarrhea, death (“rabbit starvation”)

    • ¨Maximum rate of urea synthesis/excretion
    • at 250 g protein/d (approx. 40% kcal)

    • ¨High protein does not prevent loss of
    • lean tissue during negative energy balance.
  54. Common allergies
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  55. Possible
    advantages vegetarian 
    • ¨Lower rates of some chronic diseases
    • (CHD, hypertension, type II diabetes, obesity, some cancers)

    • ¨Other lifestyle effects? Absence or
    • moderation?

    • ¨Benefits of plant sources vs. animal                                      sources
    • of proteins
  56. Possible
    disadvantages vegetarian
    • ¨Nutrient deficiencies if uninformed –
    • B12, Fe, Zn

    • ¨Deficiencies and growth retardation in
    • children of uninformed vegetarian mothers

    • ¨Less nutrient-dense sources of lysine, methionine,
    • vitamins B12, D, Ca, Fe, Zn, riboflavin
Card Set
NDFS 200 exam 2
The NDFS 200 exam 2 at BYU Fall 12