LAB: EXP 2 (Isolation of Proteins) Flashcards
Proteins are made up of smaller units called _____
amino acids
They are essential for the structure, function, and regulation of the body tissues and organs
Proteins
Amino acids that have an amino group bonded directly to the alpha-carbon are referred to as _____
alpha amino acids
the polar group is a hydroxyl (-OH) bonded to aliphatic hydrocarbon groups
serine and threonine
the hydroxyl group (phenol) is bonded to an aromatic hydrocarbon group
tyrosine
the polar side chain contains a thiol group (-SH)
cysteine
contain amide groups in their side chains
Glutamine and asparagine
Acidic amino acids
Glutamic acid, aspartic acid
Basic amino acids
Histidine, lysine, and arginine
Classification of amino acids according to polarity
- Uncharged non-polar
- Uncharged polar
- Charge polar
Classification of amino acids according to nutritional availability
- Non-essential
- Essential
Amino acids are linked together by ‘amide groups’ called _____.
peptide bonds
During protein synthesis, the carboxyl group of amino acid at the end of the growing polypeptide chain reacts with the amino group of an incoming amino acid, releasing a molecule of _____
water
Amino acid links to another to form a peptide through _____ and _____
peptide bond, condensation
Identify the structure: Sequence of amino acid residues that serves as the backbone of a peptide chain or protein
Primary
Function of the protein depends on the _____ structure
primary
Identify the structure: Regular, repeating folding patterns
secondary
Identify the structure: the “local” ordered structure brought about via H-bonding mainly
secondary
Identify the structure: α-helix & β-pleated sheets
secondary
Identify whether α-helix or β-pleated sheets: Rod-like structure
α-helix
Identify whether α-helix or β-pleated sheets: N-H to C=O
α-helix
Identify whether α-helix or β-pleated sheets: H-bonds in 4th succeeding amino acids
α-helix
Identify whether α-helix or β-pleated sheets: H-bonds parallel to axis
α-helix
Identify whether α-helix or β-pleated sheets: typically amphiphilic
α-helix
Identify whether α-helix or β-pleated sheets: polypeptide chains are arranged side by side
β-pleated sheets
Identify whether α-helix or β-pleated sheets: H-bonds form between chains
β-pleated sheets
Identify whether α-helix or β-pleated sheets: parallel or antiparallel
β-pleated sheets
Identify whether α-helix or β-pleated sheets: more stable
β-pleated sheets
Identify the structure: The way the segments of the protein fold in 3 dimensions
tertiary
Identify the structure: overall folding of domains
tertiary
Identify the structure: specific overall shape of a protein
tertiary
Identify the structure: cross links between R-groups of amino acids
tertiary
Cross links in tertiary structures happen in:
o Disulfide
o Ionic
o Hydrophobic
Identify the structure: Interaction between different polypeptide chains to produce an oligomeric structure
quaternary
Identify the structure: Aggregates of two or more protein chain connected by weak non-covalent interactions
quaternary
Identify the structure: Proteins with two or more chains
quaternary
Yield only amino acids upon hydrolysis
Simple proteins
Simple proteins + non-protein substances
Conjugated proteins
Catalytic protein example
Enzymes
Transport protein examples
Hemoglobin, transferrin, albumin
Storage protein examples
Ovalbumin, casein, gliadin
Contraction protein examples
Actin, myosin
Gene regulation protein examples
Histones, non-histone nuclear
Regulatory protein examples
Hormone, repressor proteins
Immune protein examples
Antibodies, fibrin, complement
Structural protein examples
Collagen, elastin, keratin
Neurotransmission protein examples
Receptor proteins
polypeptide chain/s folded into spherical or globular shape
globular protein
soluble in aq. system
globular protein
polypeptide chains arranged in long strands or sheets
fibrous protein
water insoluble
fibrous protein
Soluble in water and dilute aqueous solutions
Albumins (Plasma)
Soluble in dilute salt solutions but are insoluble or sparingly soluble in water
Globulins (Serum)
Soluble in dilute solutions of acids and bases; insoluble in neutral solvents
Glutelins (Flour)
- Soluble 50-90% alcohol
- Insoluble in water, neutral solvents, or absolute alcohol
Prolamins (Store protein in plants)
Albumin-like that is insoluble in most ordinary solvents
Albuminoids/Scleroproteins
A loss of three-dimensional structure sufficient to cause of loss of function
Protein Denaturation
Denaturating agents
- Strong acids and bases
- Organic solvents
- Detergents
- Reducing agents
- Salts (salting in and salting out)
- Heavy metals
- Temperature
Type of protein hydrolysis: uses a strong acid or base + high temperature
Complete hydrolysis
Type of hydrolysis: Most commonly used reagent is 6N HCl
Acid hydrolysis
In acid hydrolysis: ___ and ___ are partially destroyed
cys and tyr
In acid hydrolysis, ___ is completely destroyed
trp
In acid hydrolysis, ___ and ___ are incompletely liberated
val and ile
In acid hydrolysis, ___ and ___ are racemized and destroyed
ser and thr
Type of hydrolysis: uses NaOH or KOH
basic hydrolysis
Advantage of basic hydrolysis
trp not destroyed
Disadvantage of basic hydrolysis
arg, asn, gln, ser are destroyed
Type of hydrolysis: uses enzyme called protease
Incomplete/partial hydrolysis
_____ (eg. acid, base, enzyme) are needed to facilitate the hydrolysis of peptide bonds
Catalysts
type of hydrolysis: presence of proteolytic enzymes results to partial or selective hydrolysis of polypeptide to yield a mixture of peptide fragments.
Enzymatic hydrolysis
enzymes that hydrolyze peptide bonds at specific sites
proteases/peptidases
Advantage of incomplete/partial hydrolysis
Amino acids are not affected
Type of hydrolysis: requires certain temperature & pH conditions for optimum activity of enzymes
Incomplete/Partial hydrolysis
Type of exopeptidase: cuts C-terminal residues except R,K and P
Carboxypeptidase A
Type of exopeptidase: cuts C-terminal residues except R,K
Carboxypeptidase B
Type of exopeptidase: cuts most N-terminal except when P is the next residue
Aminopeptidase
Type of endopeptidase: cuts C side R & K
Trypsin
Type of endopeptidase: cuts C side of F, Y, W
Chymotrypsin
Type of endopeptidase: cuts C side of hydrophobic groups/aromatic R-groups
Papain
Used in precipitation separation method and their solubility
- ammonium sulfate (sol)
- polyethylene glycol (sol)
Properties of proteins being considered during separation
o Charge
o Molecular size, shape
o Solubility
o Affinity to a ligand
o pI/IpH
A procedure in which the pH of the protein mixture is adjusted to the pI of the protein to be isolated to selectively minimize its solubility.
Change in pH
Casein: source and isolation method
- Source: Skimmed milk
- Isolation method: Isoelectric precipitation
Casein: type of protein
Phosphoprotein
Isoelectric point of casein
4.6
Mechanism of casein separation
PO4—3 interacts (ionic) with Ca+2 leading to polymerization of casein
Albumin: source and isolation method
- Source: Skimmed milk
- Isolation method: Denaturation and Coagulation by heat
Albumin: type of protein
Globular protein (sol in water and diluted salt solutions)
Second major protein in bovine milk and can serve as a regulator protein in lactose biosynthesis
Albumin
Albumin is a _____ that can bind to several metal ions like calcium and zinc
metalloprotein
Myoglobin: source and isolation method
- Source: Beef muscle
- Isolation method: Salt-induced precipitation
Color of isolated myoglobin precipitate
White
Gluten: source and isolation method
- Source: Wheat flour
- Isolation method: Solubility difference
Gives bread its structure, texture, and elasticity
Gluten
Gluten is a composite of _____ and ____, which exist, conjoined with starch
Prolamin and glutelin
T/F: the isolated gluten should be positive of the iodin test
F. Should be negative.
Role of gluten in bread making
traps the CO2 and gives off chewiness
Solution used to test the complete removal of starch
I2
Appearance of isolated gluten
Yellowish-white solid, tough, elastic, sticky