Qualitative Reaction of Proteins Flashcards
polypeptides with at least
50 amino acid residues and could
have hundreds and even thousands
of amino acid residues
proteins
structure of
protein is largely determined by their
amino sequence as postulated by this
dogma
Anfinsen’s dogma
Hierarchy of structural organization
of proteins
➢ Primary structure (1o
➢ Secondary structure (2o
➢ Tertiary structure (3o
➢ Quaternary structure (4o
amino acid
sequence of polypeptide which starts
at the N-terminal amino acid and
ends with C-terminal amino acid
primary structure
refers to the
local folding of a short segment of a
peptide into specific configurations
such as α-helix, β-sheet, or random
coil
secondary stucture
over-all threedimensional shape of the protein
which can either be globular or
fibrous in conformation
tertiary structure
– association of
the various sub-units of a multimeric
protein
quaternary structure
play countless roles
throughout the biological world, from catalyzing chemical reactions to
building structures of all living things
protein
made up of carbon,
oxygen, nitrogen, hydrogen, and
sulfur atoms
amino acid
– interact with
oppositely charged amino acid or
water
charged amino acid
protein chian fold into this
can form regular patterns of
hydrogen bonds between the
backbone atoms of nearby amino
acids
alpha-helix
backbone atoms of the
chain can interact side-by-side to
form
beta-sheets
forms a pocket to hold
heme, a small molecule with an iron
atom at the center that binds oxygen
hemoglobin
its flexible arms protect
the body from disease by recognizing
and binding to foreign molecules and
thus preventing the viral RNA or DNA
to enter the cell
antibodies
forms a strong triple helix
that is used throughout the body for
structural support
collagen
moves ions across
cell membranes allowing the
synchronized contraction of muscles
calcium pump
small, stable protein that
can easily maintain its shape while
travelling through the blood to
regulate blood sugar level
insulin
enzyme that has a
catalytic site that begins the
breakdown of carbohydrates in our
saliva
alpha-amylase
forms a hollow shell that
stores iron from our food
ferritin
put together a model
of myoglobi
John Kendrew
proteins are made up
of these
amino acid
used to detect the
presence of a peptide bond and uses
alkaline/basic copper sulfate reagent
biuret test
what does biuret test uses as an reagent
alkaline
basic copper sulfate
forms a
coordination complex with the
nucleophilic nitrogen atom of
the peptide bond which
manifests as violet complex
copper ion
violex complex is called what in biuret test
biurety complex
color of biuret when negative
blue
color of biuret when positive
deep purple
– used for the
detection of free amine on amino
acids or peptides where ninhydrin
reagent forms an intense violet
colored complex called Ruhemann’s
purple
Ninhidyrin test
violet colored complex in ninhydrin test
Ruhemann’s purple
is a chemical test that can differentiate between an alpha-amino group and a free amino acid.
ninhydrin test
In this test, ninhydrin is used as an oxidizing/reducing agent that reacts with the amino group of the analyte
oxidizing
positive ninhydrin test is what color
purple-colored complex
what is the color of ninhydrin when proline is present
yellow
Proline is an _____ and it reacts with ninhydrin to form a yellow-colored complex
imino acid
This is because the reaction of proline with ninhydrin yields an ___ salt, which is yellow-orange in colo
iminium
used to
distinguish the presence of
tryptophan or tyrosine which forms
yellow-colored product with nitric
acid
Xanthoproteic test
tryptophan or tyrosine forms a yellow-coloredp roduct with what reagent
nitric acid
what structure of these amino
acids reacts with nitric acid
forming a yellow by-product
benzene ring
used to confirm the
presence of tyrosine by the formation
of reddish-brown product with
mercury in nitrous acid
Millons test
reagent that tyrosine reacts with in Millons test
acificied mercuric sulphate solution
Detects tyrosine by the
reaction of its phenolic group
with the reagents, producing a
reddish-brown complex
millons test
used for the
detection of tryptophan which forms
a violet ring upon reaction with
glyoxylic acid and conc. Sulfuric acid
hopkins-cole test
Detects tryptophan by the
reaction of its indole ring
reacts with the reagents
hopkins-cole test
Manifested in the formation of
violet ring in between the layer
of the sample and sulfuric acid
positive hopkins-cole test
reagent in Hopkins-cole test
glyoxylic acid
disruption of these
stabilizing forces and bonds in a
protein that results to the disruption of its native conformation and
subsequent loss of its biological
function
denaturation
Physical manifestations that can
denature a protein
mechanical agitation
heat
Chemical agents that can denature a
protein:
➢ Acids
➢ Bases
➢ Salts
➢ Organic solvents
➢ Detergent
➢ Alkaloids
➢ Heavy metals
Chaotropic agents include (5)
– guanidine
HCl
urea,
βmercaptoethanol,
dithioeitol
can disrupt specific
stabilizing bonds or forces in
the protein which leads to
alternation in its structure as
manifested by the
precipitation of the protein
from the solution
chaotropic agents
Stabilizing bonds or force in proteins
H-bond
Salt bridge
Hydrophobic interaction
disulfide bond
Fill in the blanks
Carefully separate egg white from
yolk of one medium-sized chicken
egg. Discard _____. Measure the
volume of egg using a ______ . Transfer to a 250 ml
beaker and dilute with equal
volume of _____ ______. Use
as a sample for subsequent
analysis
yolk
graduated cylinder
phosphate buffer
Transfer _____ mL of the egg white
solution to _____separate test tubes
and label them properly. Add the
ff reagents to the respective test
tubes:
2 mL
5 test tubes
Test tube 1 – 2.00 ml of
____solution, heat for
5 minutes in water bath or
until a color change is
observed
ninhydrin solution
test tube 2 – 5 drops of
concentrated ___ _____
(xanthoproteic test), heat
for 5 minutes in water bath
or until a color change is
observed
nitric acid
Test tube 3 – 5 drops of
______ _____, heat for 5
minutes in water bath or
until precipitate is formed
Millon’s reagent
Test tube 4 – 5 drops of
_____ ____ (HopkinsCole reagent), tilt the tube
slightly and carefully add
2.0 mlo of concentrated
sulfuric acid to form two
layers. Wait for color
change
glyoxylic acid
Test tube 5 – 2 mL of ______
solution and 1 mL of 0.200
M _____. Shake vigorously
and incubate until a color
change is observed
biuret
NaOH
Transfer 2 mL of the egg white
solution to _ separate test tubes
and label them properly. Add the
following reagents to the
respective test tubes
8
Test tube 1 – 0.200 M ___
drop by drop until change
occurs
HCl
test tube 2 – 0.200 M ____
drop by drop until change
occurs
NaOH
Test tube 3 – 0.200 M _____
____drop by drop until
change occurs
lead acetate
Test tube 4 – 0.200 M _____
drop by drop until change
occurs
urea
Test tube 5 – 0.200 M ____
acid drop by drop until
change occurs
tannic
test 6 – 70% ____
drop by drop until change
occurs
ethanol
Test tube 7 – _____in water
bath until change occurs
heat
Test tube 8 – ______
vigorously until change
occurs
shake
– increases kinetic energy,
causing atoms of proteins to vibrate.
The vibrating motion disrupts or
breaks the weak hydrogen bonds and
dispersion forces
heat
The accelerated vibration can
disrupt the _____ ______ ,
_______ ______, as
well as ___ _____forces,
causing the unfolding of
protein’s 3D structure
hydrogen bond
hydrophobic interactions
van der waals
a hydrogen bonds to
polarized areas of charge, such as
peptide groups.
urea
Mutual influence weakens the
intermolecular bonds and
interactions, weakening the
overall secondary and tertiary
structure
urea
capable of engaging in
intermolecular hydrogen bonding
with protein molecules, disrupting
intramolecular hydrogen bonding
within the protein
ethanol
combine with positively
charged amino groups in proteins to
disrupt ionic bonds
tannic acid
normally, a person hav
protein
– large amount of protein
in urine may mean that you have a
problem with your kidneys
proteinuria
Early sign of chronic kidney
diseases (CKD
proteinuria
Needed for the
synthesis of proteins
phenylalanine
Important precursor
of amino acid Ltyrosine (Tyr)
phenyalanine
Used as an energy
fuel
phenylalanine
too much of this when converted into
phenylpyruvate, and
the individual usually
develops seizures,
brain damage, and
mental retardation
phenyalanine
too little of this causes growth
failure, loss of
muscle mass, and
organ damage
phenylalanine
Play a significant role
in the regulation of
energy metabolism,
locomotor activity,
and eating behavior
tyrosine
too much of this can cause migraine headaches
and hyperthyroid
conditions
tyrosine
too little of this is associated with
behavioral and
learning disorders,
depression, anxiety,
and inability to deal
with stress
tyrosine
role in
brain serotonin
synthesis is an
important factor
involved in mood,
behavior, and
cognition
tryptophan
high levels is
associated with
headaches and
selective serotonin
reuptake inhibitor
treatmen
tryptophan
Low levels are
commonly correlated
with depression,
insomnia, and
schizophrenia
tryptophan
