P1. Intro + amino acids
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5 biochemical/physiological roles of proteins
• play a role in structural components of skin, muscles, tendons and bones • serve as catalytic agents for specific reactions (ie enzymes) without which life would not be possible • serve as regulating agents or hormones • act as antigens and serve as antibodies • serve as carriers of O2 and CO2 (myoglobin and hemoglobin)
Proteins in diet provide (3)
• amino acids • nitrogen • energy (4cals/g)
which amino acids are essential? what does essential mean?
• essential = cannot be synthesized at all or fast enough to meet the body’s requirements • histidine, isoleucine, leucine, methionine, phenylalanine, threonine, tryptophan, valine, lysine
do animal or plant proteins have all essential amino acids?
• animals do! • plant proteins are generally deficient in one or more of the essential acids
food scientists look beyond nutritional aspects of food proteins to focus on their ____________
functionality
protein functionality refers exclusively to ? - 5 examples
non nutritional functional properties of proteins in food systems - water binding capacity - emulsification capacity - gel-forming ability - coagulating properties - dough-forming abilities
functional properties (increase/decrease) the value of proteins to manufacturers and consumers
increase!
protein functionality is important from a ____________ standpoint
palatibility
bread is much more palatable than whole kernels of wheat –> ability to leaven dough is due specifically to __________, a protein with peculiar _________ properties not found in other grains
• gluten • elastic
water holding capacity of proteins is important for __________ or __________ of a number of food products
• texture • juiciness
monosodium glutamate is a well-known _______ _________
protein hydrolysate
stability of proteins and the reactions they undergo during processing have to be considered –> __________ vs ______________
nutritional loss vs functionality loss
catalytic behavior in form of enzymes can be both ___A______ and _____B_______ - examples of B
A: beneficial B: detrimental - degradation of many food components either autolytically (endegenous enzymes) or as exocgenous enzymes supplied by microorganisms contaminating food
examples of uses of enzymes in food processing (4)
• proteases to tenderize meat • lipase to speed up flavor development in cheese • amylase to manufacture corn syrups/sugar (soft drinks) • glucose oxidase to remove headspace oxygen from food packages
plant sources vs animal protein sources –> 3 benefits of plant + 2 benefits of 1 type of animal
• plant source: abundant, cheaper and more energy efficient to produce than animal or dairy source • dairy sources: better cost and higher functionality than casein, egg albumin, soybean and other protein sources
meat analogs are made of ____ protein via ___________ using extrusion technology
• soy protein • texturization
what makes use of pollock to make analogs of crab meat and scallops?
surimi
how many amino acids make up proteins?
generally 20 - but actually more than 20! (20 factorial) combinations and permutations
what is the secret to the success of living systems? (in regards to proteins)
their ability to build an almost infinite variety of protein structures, each with own unique chemical and physical properties
what is the general formula of an amino acid?
alpha carbon attached to COOH, NH2, H and functional group
what defines an amino acid?
the fact that an amino group (NH2) and a carboxylic acid (COOH) are attached on the same carbon (alpha carbon) - presence of these 2 functional in such close proximity leads to some unusual properties
describe ion charges of amino acid (protonated/deprotonated?)at low pH, at neutral pH and at high pH
• low pH: NH3+ and COOH • neutral pH: NH3+ and COO- • high pH: NH2 and COO-
what is a zwitterion? - what H moves where? why? - when does it happen?
• NH3+ and COO- on the same amino acid • the aa does not have they neutrally charged structure (NH2 and COOH) –> instead H from COOH moves to NH2 • at the amino acid’s isoelectric point
formula for isoelectric point
pI = (pk1 + pk2)/2