Ch. 7 - Proteins Amino Acids

Protein quality

*high-quality* (complete protein) - contains all essential amino acids; well digested & absorbed by the body. ie.) meat, fish, poultry, eggs, milk, & milk products *low-quality* (incomplete protein) - lacks or contains inadequate amounts of one or more of the essential amino acids digestibility & amino acid composition of a protein are two key factors to determining protein quality

Acid-base balance

proteins maintain ABB which is the proper pH of body fluids. pH = ~ 7.35 - 7.45 (slightly basic)

Define: anaphylaxis

serious drop in blood pressure that occurs when sensitive people are exposed to food allergens; can be fatal

Food Allergies p. 208

symptoms: hives (raised red bumps), swollen or itchy lips, scaly skin rash (eczema), difficulty swallowing, wheezing & difficulty breathing, abdominal pain, vomiting, & diarrhea

Food Intolerance

unpleasant physical reactions, including headaches & intestinal discomfort NOT the same as food allergy as food does NOT trigger immune response

Protein Synthesis p. 193

body makes proteins by using info coded in DNA & cells assemble the 20 amino acids into specific sequences according to the info provided *peptide bond* - connection between amino acids *peptides* - contain two or more amino acids

Protein digestibility corrected amino acid score (PDCAAS)

most commonly used tool to measure protein quality; to calculate amino acid composition score: amount of each essential amino acid in 1 g of food divided by "ideal" amount of each essential amino acid in a reference protein protein lacking an essential amino acid will have a score of 0 PDCAAS is calculated by: amino acid score * protein's digestibility score most animal proteins, as well as soy = 1.0

Define: limiting amino acids

essential amino acids that are in relatively low amounts ex.) tryptophan, threonine, lysine, & sulfur-containing amino acids methionine & cysteine

Protein Deficiency

people suffering from alcoholism, anorexia nervosa, or certain intestinal tract disorders are at risk.

Define: protein turnover

process of breaking down old or unneeded proteins into their component amino acids & recycling them to make new proteins; constantly occuring

Acceptable Macronutrient Distribution Range (AMDR) p.202

protein comprised ~15% of typical American energy intake for a day AMDR = 10 - 35% of energy from a protein

Define: gluten

protein in wheat, barley, & some other cereal grains contains the polypeptide gliadin

Protein denaturation

protein undergoes conditions that alter its natural folded & coiled shape normal protein --> heat, acid, alcohol, whipping --> denatured protein **CANNOT return to original state

Non-animal protein food soureces

Beans, nuts, seeds grains, & some vegetables *no naturally occurring food is 100% protein

Nitrogen Balance

*nitrogen equilibrium* - healthy adult meets protein & energy needs *positive nitrogen balance* - body retains more nitrogen than it loses as proteins are being added to tissues; occurs during periods of rapid growth *negative nitrogen balance* - body loses more nitrogen than it retains; occurs during starvation, serious illness, or injury

Protein structures

*primary structure* - linear *secondary structure* - coiling *tertiary structure* - 3D form *quaternary structure* - large complex such as hemoglobin

Protein digestion p. 198

*stomach* --> proteins denaturized by stomach acid & partial digestion by pepsin --> *small intestine* --> *pancreas* secretes enzymes including trypsin & chymotrypsin --> *small intestinal cells* --> final digestion occurs within absorptive cells --> *liver* --> amino acids enter hepatic portal vein & travel to liver --> *rectum* --> very little dietary protein excreted in feces

Basic steps of protein synthesis

-DNA unwinds exposing a gene -gene undergoes transcription, forming mRNA -mRNA transfers info from nucleus to ribosomes -ribosomes "read" mRNA -RNA molecule conveys a particular amino acid to the ribosome -at the ribosome, amino acid attaches to the peptide chain

Protein RDA

0.8g per kg of body weight 0.8 * weight = protein RDA protein needs increase during pregnancy, breastfeeding, periods of rapid growth, & recovery from serious illnesses, blood losses, & burns

Gluten-free flour substitutions p. 212

1 c wheat flour can be substituted with: 7/8 c rice flour 5/8 c potato starch flour 1 c soy flour + 1/4 c potato starch flour 1 c corn flour 1 c tapioca flour

Edema

accumulation of fluid in tissues; "swelling" may occur during starvation as protein levels in the blood decrease & some water leaks out of the bloodstream & enters the space between cells.

Celiac disease p. 211

autoimmune disorder resulting in poor absorption of nutrients in the small intestine; gluten cannot be absorbed & results in damage to the small intestine & poor absorption of nutrients symptoms: abdominal bloating, chronic diarrhea, & weight loss

Excessive Protein Intake

can lead to increased risk of certain chronic diseases, particularly heart diseases, including colorectal cancer, & prostate cancer consumption of red meats & processed red meats --> pancreatic cancer red meat --> certain breast cancers can also lead to dehydration as kidney needs more water to dilute & eliminate toxic wastes

Proteins p.190 see table 7.1 for more major functions

complex organic molecules similar to carbs (both contain C, H, & O atoms); protein also contains N atoms needed to make important biological compounds (ie. enzymes & hormones) *function* - muscle development & maintenance *units* - amino acids; 20 different amino acids *structural proteins* = collagen (cartilage, ligament & bone tissue) // keratin (hair, nails, & skin)

Protein efficiency ratio (PER)

determined by measuring the weight gain of a growing laboratory animal that consumes a known amount of a specific type of protein. weight gain is then compared against weight gain following consumption of a reference protein, usually milk (*casein*)

Protein-energy malnutrition (PEM)

diets lack sufficient protein as well as energy. *marasmus* - results from starvation; diet lacks energy & nutrients. extreme weight loss *kwashiorkor* - results from consuming adequate energy & insufficient high-quality protein --symptoms = stunted growth, unnaturally bond, sparse, & brittle hair, skin patches of discoloration, & may give a false appearance of being well fed *marasmic kwashiorkor* - results in a child with kwashiorkor who then starts to NOT consume enough energy; characterized by edema & wasting (loss of organ & muscle proteins as body tears down tissue)

Amino Acids

has a C atom that anchors a hydrogen atom & three different groups of atoms: 1.) amino (nitrogen-containing group) 2.) R group (side chain) 3.) carboxylic acid group healthy body can make 11 acids (nonessential or dispensable)

Vegetarianism p. 214

individuals who rely heavily on plant foods; may or may not include some animal foods in their diet tend to have a lower risk of obesity, type 2 diabetes, hypertension, & certain cancers

Biological Value (BV)

measure of how well & how quickly body converts food protein into body tissue protein. N grams absorbed / N grams retained = BV egg white = 100% most animal sources (milk, cheese, meat) = 90 - 100% whole soybeans = 96% rice = 83% tofu = 64% whole-wheat flour = 41%

Complementary combinations p. 203

mixtures of certain plant foods that provide all essential amino acids without adding animal proteins to make dishes with complementary AA combos consumers must know: 1.) which plant foods are good protein sources 2.) which essential amino acids are limiting or low in those plant foods