(7) Protein Flashcards
protein definition
macromolecule (polypeptides) that’s composed of amino acids liked to each other by peptide bonds
mention the origins of protein
plant origin: vegetables (soybeans, legumes)
anima origin: meat, fish, chicken, etc
shape types of protein
globular, fibrous, conjugated
function of protein for the body
regulator, builder, biological activities (hormone, enzymes,…)
ideally, how much protein should you have per day
1 gram/ body weight
amino acid definition
an organic compound that contains both an amino (-NH2) and carboxylic acid (-COOH) functional group.
*both func. groups are tied to carbon with alpha bond (a-carbon, a-amino, a-hydrogen)
amino acid is amphoteric, meaning…
it can act as an acid or base
what functional group in amino acid makes them different from one another
the -R group
what are the categories of -R group attached
non-polar alipathic group
polar uncharged group
aromatic group
positive/negative ionic group
what does non-polar alipathic -R group means and give examples
the R group is hydrophobic and non-polar
*glycine, alanine, valine, leucine, methonine, isoleucine
what does polar uncharged -R group means and give examples
the R group contains hydroxyl or amino groups. they have hydrophilic properties
*serine, threonine, cysteine, proline, asparagine
what does aromatic -R group means and give examples
the R group is composed of aromatic or N ring structure
*phenylalanine, tyrosine, tyrptophan
what does positively charged -R group means and give examples
the R group has an amide group and can form positive ions ph< 7.0
*lysine, argininem hystidine
what does negatively charged -R group means and give examples
the R group has a COOH group that can form negative ions ph>7.0
*aspartic acid, glutamic acid
what is essential amino acid
amino acids that can’t be synthesized by our body but are required in our diet
*isoleucine, leucine, methionine, phenylalanine, threonine, triptophan, valine, lysine, hystidine (child), arginine (infant)
isomer definition
compounds that have the same molecular formula but are structurally different
two optical isomes/mirror images of each other molecules that exhibit handedness are said to be …… and the mirror images are referred to as ……..
chiral, enantiomers
what’s the isomer of D-alanine
L-alanine
what is isoelectric point and how does it relate with amino acid
the ph at which a molecule carries no electrical charge
*it also means that the Ph of whichamino acid molecule is uncharged
what is pka : ph in amino acid
50% ionized : 50% unionized
protein have the potential to function as an acid or a base, depending on the ph. this is the definition of amino acid properties
amphoteric
what is polymerization
a process where monomers combine together to produce a polymer
how many polymerization type
dipeptide, oligopeptide, polypeptide, protein
what type of bond connects the monomers in a polymer
peptide bond
what is a peptide bond
covalent bonds that connects the amine (-NH2) of AA1 and carboxyl group (-COOH) of AA2
mention some properties of peptide bonds
- peptide bonds are shorter and stronger than C-C bonds, but weaker than C=C
- cannot rotate freely
- when peptide bond is formed, one water molecule is released (condensation polymerization)
*diagram on page 17 on week 7
explain the different structures of protein
primary structure= linear sequence from N terminal to C terminal
secondary= alpha helix & beta sheets
tertiary= 3d conformational shape & shape is usually globular
quartenary= 2 or more different polypeptides in a 3d space
*see diagram on page 17 week 7
difference between alpha helix and beta sheet
alpha helix= the carbonyl (C=O) of one amino acid is hydrogen bonded to the H (N-H) of an amino acid that’s four down the chain. shape is spiral.
b-pleated sheet= two or more segments of polypeptides chain line up next to another. shape is sheet-like structure.
what kind of bonds chains the polypeptides together in a tertiary structure
hydrogen bond, ionic bond, hydrophobic interaction, disulfide bond
the different types of protein
globular protein= spherical in their tertiary structure. (albumin, globulin, histone, protamines)
fibrous protein= insoluble, elongated protein molecules (collagen , elastin)
conjugated protein= protein combined with some other type of compound, carbo or lipids. (lipoprotein, metalloprotein, nucleoprotein, phospoprotein)
effects of food process or storage to protein
- denaturation (by heating) -> change in solubility
- oxidation (catalyzed by light) -> change in flavor
- enzymatic degradation -> change in texture and flavor
- freezing -> change in conformation and solubility
explain protein denaturation
distruption and possible destruction of both secondary and tertiary structure. it uncoils the conformation into a random shape.
*primary structure are not affected because denaturation only affect peptide bond (primary structure is only a sequence of amino acid)
what are the physical observation during denaturation process
precipitation or coagulation of protein
what bonds are broken down during unfolding of structure (denaturation)
hydrogen bonds. covalent bonds are undistrupted
what happens to protein functional properties during denaturation
functional properties are changed
daily examples of protein denaturation in food
frying eggs and warming milk
factors of protein denaturation
heat, alcohol, acid or base, heavy metals, reducing agents
physicochemical properties of proteins
- hydration (water holding capacity and viscous forming
- solubility (important for extraction process)
- thickener
- gelling agent (important for processed meat and fish products)
- texture (heat coagulation and film forming. fiber structure in meat)
food application of physicochemical properties of proteins
- emulsifier
- foam forming (foam of egg whites)
- dough forming (viscoelatic gluten protein in bread)
- maillard reaction (sugar and protein/amino acid)
how does viscosity affect protein
viscosity of a protein solution is increased by denaturation of protein
functional properties of proteins in relation with water
wet ability, swelling, rehydration, water holding, solubility
functional properties of proteins in relation with water and proteins
viscosity, gelling, fiber forming, dough forming
functional properties of proteins in relation with lipids/gases
emulsification, foaming ability, foam stabilization
characteristics affected by food proteins
hydration, taste, appearance, viso-elasticity
what is protein gelation
gelation is a result of denaturation. it’s a 3d network of protein fibers that develops high structural rigidity.
the gel matrix of protein can hold water, fat, and other food ingredients (gelatin desserts, tofu, yoghurt)
what is the water holding capacity of protein
the ability of protein to bind water is related with the presence of hydrophilic and charged groups in the structure (meat retains water when cut, heat, or grinding)
