PROTEINS Flashcards
Proteins came from the Greek word ______ meaning “pre-eminence” or of first importance.
PROTEIOS
are chains of amino acids
Peptide bond
Proteins are made up of _ _ _ _ ; usually S and traces of Fe, Cu, I, Mn, Zn etc.
CHON
these are true proteins found abundantly in both plants and animals.
Simple Proteins
soluble in water and dilute neutral salt solutions
Albumins
Examples of Albumins
serum albumin - blood
lactalbumin - milk
ovalbumin - eggwhite
soluble in neutral dilute salt solutions but NOT in water
Globulins
Examples of Globulins
ovoglobulin - egg white
edestin - hempseed
myosinogen - muscles
legumin - peas
serum globulin - blood
soluble in dilute acids and alkalis but insoluble in neutral solvents
Glutelins
Insoluble in ordinary solvent but soluble in 70% alcohol at about neutral point.
not coagulable by heat.
Prolamines
soluble in water, dilute acids and alkalis but not in dilute ammonia
not readily coagulated by heat
strongly basic and occur in tissues in the form of salt combinations with acid substances like heme of the hemoglobin
Histones
Examples of Histones
globin - hemopglobin
Thymus histone
Scobrone - mackerel
contains small number of amino acids
soluble in water and dilute acids and alkalis
not coagulated by heat
Protamines
Example of Protamines
Salmin - salmon sperm
soluble in water and neutral solvents
Scleroproteins (Albumonoids)
Examples of Scleroproteins
Keratin - epidermal tissues
elastin - ligaments
collagen - hides, bones and cartilages
made up of protein molecules combined with non-protein groups
Conjugated proteins
Conjugated Proteins
Nucleoproteins
Glycoproteins
Phosphoproteins
Chromoproteins
Lipoproteins
Classification of Proteins according to Hydrolysis Products
Simple Proteins
Conjugated Proteins
Derived
Simple Proteins
Albumins
Globulins
Glutelins
Prolamines
Histones
Protamines
Scleroproteins
combination of histones and protamines with NUCLEIC ACIDS
Nucleoproteins
obtained from grandular tissues and germ of grains
chromatins
compounds of proteins with a carbohydrate component
Glycoproteins
Examples of Glycoproteins
mucin - saliva
tendomucoid - tendons
osseomucoid - bones
have the prosthetic group (H3PO4) joined to the protein molecule
Phosphoproteins
Examples of Phosphoproteins
casein - milk
vitelin - egg yolk
protein compounds with hematin or similar pigments in their molecules
Chromoproteins
examples of Chromoproteins
cytochromes, hemoglobin, rhodopsin
have fatty substances combined with their molecules like lecithin, cephalin, etc.
Lipoproteins
lipoproteins are present in:
blood serum, brain tissue, cell nuclei, egg yolk and milk
include substances formed from simple and conjugated proteins
Derived
2 divisions of derived proteins
Primary Protein Derivatives, Secondary Protein Derivatives
have undergone slight INTRAmolecular rearrangement through the hydrolytic action of certain physical and chemical agents
synonymous with denatured proteins
Primary Protein Derivatives
examples of Primary Protein Derivatives
Proteans, Metaproteans and Coagulated Proteins
insoluble substance resulting from preliminary action of water, dilute acids or enzymes
Proteans - myosann, edestan
are products of further hydrolysis
soluble in weak acids and alkalies but insoluble in neutral salt soln.
Metaproteans - acid metaproteans / alkali metaproteans
Insoluble products resulting from either the action of heat, alcohol, UV rays or simple mechanical shaking
Coagulated Proteins - cooked
products of MORE extensive hydrolysis
mix of fragments of original protein varying in composition and size
NOT coagulated by heat
Secondary Protein Derivatives
Examples of Secondary PD
Primary Proteoses, Secondary Proteoses, Peptones, Peptides
are combinations of 2 or more amino acids
Peptides
According to Biological Significance
Transport Proteins - carry/ circulate - hemoglobin (O2), serum albumin(fatty acids)
Storage Proteins - store - Ovalbumin, Ferretin (liver protein)
Protection Proteins - defense - antibodies
Catalytic Proteins - catalyze - enzymes
Structural Proteins - mechanical support - collagen (bones) Keratin (Hair)
Contractile Proteins - nerve impulses - myosin(muscle)
Chemical Proteins - hormones
According to conformation/ shape:
Fibrous - Collagen, Elastin, Keratin
Globular - Antibodies, Enzymes
Mixed - both
are chains of amino acids
Peptide bonds
two amino molecules can be covalently joined through a substitute linkage termed peptide bond to yield ____?
Dipeptide
three amino acids can be joined by 2 peptide bonds to form ___?
tripeptide
4 amino acids can be linked to form a _____?
tetrapeptide
5 amino acids form ______?
pentapeptide
few amino acids are joined, the structure is called ____?
oligopeptide
when many amino acids are joined, the product is called ______?
Polypeptide
“protein” and “polypeptide” are sometimes used interchangeably, polypeptide generally have molecular weights below 10,000 while PROTEINS have higher molecular weights
TRUE
The peptide bond is a ________ bond.
partial double bond
is trans in nature and there is no freedom of rotation because of the partial double bond character
C-N bond
the angles of rotation that determine the spatial orientation of the peptide chain
Ramachandran angles (by Dr GN Ramachandran) / Gopalasamudram Narayanan Ramachandran
Properties of Proteins
Physical and chemical properties
are color less, odorless and tasteless except protein hydrolyzates
CHON
Proteins are precipitated by:
Organic Acids
Inorganic Acids
Salts of Heavy metals
Alkaloidal Reagents
High concentration of neutral salt solution / salting out
Alcohol
Levels of organization of CHON:
Primary Structure
Secondary Structure
Tertiary Structure
Quaternary Structure
linear arrangement of amino acid in a polypeptide chain joined together by means of peptide linkages (e.g. Insulin)
Primary Structure
BOTH above, BOTH BELOW, both left, BOTH RIGHT
Cis Isomer
1 above and 1 below; 1 left and 1 right
Trans Isomer
Involves the folding of the polypeptide chain.
particularly stable arrangements of amino acid residues giving rise to recurring structural patterns
steric relationship of amino acids
Secondary Structure
2 types of Secondary Structure
Alpha Helix and Beta Pleated Sheet (Pauling & Corey)
secondary structure chain formed due to INTRAmolecular H- bonding
has a spiral structure
Alpha Helix
2 amino acids that disrupt the regularity of the alpha helical backbone conformation
Proline & Glycine
it means within molecules
INTRAMOLECULAR
a secondary structure formed due to INTERmolecular H- bonding
are formed by similar hydrogen bonds between continuous sequences of carbonyl and amino groups
Beta-Pleated Sheet
it means between different peptides
INTERMOLECULAR
a weak bond due to the weak attraction between a a+H and lone pairs of an atom
H-Bond
furthermore unfolding of polypeptide chains due to formation of bonds like H-Bond, peptide bond, covalent bond, disulfide bond, ionic bond and hydrophobic interactions
Tertiary Structure
is the term used to denote a compact globular functional unit of a protein
Domain
Most complex aspect of protein strand
involves polypeptide chains tightly woven with each other
stabilized by relatively weak interactions
e.g. Hemoglobin
Quaternary Structure
destruction of the secondary, tertiary and quaternary structures of CHON leading to changes in its physical, chemical and biological characteristics
Denaturation of Proteins
2 types of Denaturating Agents
Physical (heat, UV rays, high pressure)
Chemical (acids & bases,, physical-increased viscosity, Chemical - decreased solubility, Biological - increased digestibility of enzymes)
splitting enzyme by acids, bases and protein
Hydrolysis
Denatured proteins are easily digested in the stomach as compared to undenatured proteins
true
