Download 1D17 – BMI201 Page 1 of 3 Code Questions Answers 1 Discuss the

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1
Questions
Discuss the functions Of
Albumin and Its Clinical
Significance.
2
Explain specificity
enzymes.
3
Discuss
Stereoisomerism.
1D17 – BMI201
of
Answers
Plasma albumin performs the following functions:
1. Osmotic function: helps in maintaining the intra vascular colloidal osomotic
pressure. Due to its high concentration and low molecular weight, albumin
contributes to 80% of the total colloidal pressure. This pressure prevents the
flow of the plasma into the tissue spaces by which the fluid volume inside the
blood vessels. Albumin play a major role in maintaining blood volume and
body fluid distribution.Decrease in albumin level leads to fall in the osmotic
pressure and in turn leads the escape of fluid resulting in edema.
2. Transport function: transport many hydrophobic substances like
unconjugated bilirubin, free fatty acids, steroid harmones, thyroxine, drugs,
calcium, copper and other heavy metals.
3. Nutritive function: Serves as a source of aminoacids for the tissue protein
synthesis . albumin contains almost all proteins in good proportions.
4. Buffering function : All proteins show buffering action due to the presence of
the aminoacids histidine. Since albumin present in high concentration in
blood and also contains good number of histidine residues, it shows
maximum buffering capacity.
Hypoalbuminemia: seen in following conditions
Liver disease: chronic liver failure, cirrhosis
Kidney diseases: Nephrotic syndrome- Albuminuria
Microalbuminuria
Malnutrition/ malabsorption
Burns and trauma
Enzymes are highly specific in their reaction. Occurrence of thousands of
enzymes in biological system might be due to this specific nature of enzymes.
There are three types of enzyme specificity and they are as follows:
1. Stereospecificity: also called optical specificity. Stereo isomer are the
substances which have same molecular formula but differ in their structural
configuration. The enzyme act only one isomer and therefore exhibit stereo
specificity.
e.g L-aminoacid oxidase and D aminoacid oxidase act on L &D aminoacid
respectively
2. Reaction specificity : the same substance can undergo different types of
reaction and each reaction is catalyzed by different enzymes and this is
referred as reaction specificity.
3. Substrate specificity :The substrate specificity varies from enzyme to
enzyme. They are of three types
a. Absolute substrate specificity- certain enzymes act only on
one
type of substrate. E.g glucokinase acts on glucose
b. Relative substrate specifity- some enzymes act on structurally related
substances. E.g hexokinase acts on glucose, fructose, mannose.
c. Broad specificity: certain enzymes act on closely related compounds.
E.g trypsin hydrolyses peptide linkages next to arginine and lysine in any protein.
Important character of monosachharides. Stereoisomers are the compounds that
have the same structural formulae but differ in their spatial configuration. These
include1. Enantiomer: D and L sugars are referred to as enantiomers. Their structures
are mirror images of each other. Only D-sugars are utilized by humans.
Eg. D-glucose and L-glucose are termed D and L form depending on the
arrangement on H and OH on the penultimate carbon atom. When the sugar
is has OH group on the right, this form is D-isomer. If the OH group is on the
left side thenit is L-isomer. Figure 3.7
2. Anomers: Sugars in solution exist in ring form and not in ketosugar forms
furanose ring structure.
Carbon 1 after ring formation becomes asymmetric and is called anomeric carbon
aataom. If the two sugars differ in the configuration at only C1 in case of
aldoses and C2 in ketoses then they are known anomers and are
represented as alpha and beta sugars.
3. Epimers: the isomers formed due to variations in the configuration of H and
OH around a single carbon atom in sugar molecule are called epimers.
Page 1 of 3
4
Explain the properties of
proteins.
5
Discuss
inhibition.
1D17 – BMI201
Enzyme
Mannose is 2-epimer of glucose because these two have different
configuration onlyl around C2. Similarly galactose is 4-epimer of glucose
because these two have different configuration only around C4
Proteins are characterized by their size and shape, amino acid composition and
sequence, isoelectric point, hydrophobicity, and biological affinity. Differences in
these properties can be used as the basis for separation methods in a purification
strategy. The chemical composition of the unique R groups is responsible for the
important characteristics of amino acids, chemical reactivity, ionic charge and
relative hydrophobicity. Therefore, protein properties relate back to the number
and type of amino acids that make up the protein.
1. Size: size of proteins is usually measured in terms of molecular weight
although occasionally the length or diameter of a protein is given in
angstroms. The molecular weight of a protein is the mass of one mole of
protein, usually measured in units called daltons.
2. Amino acid composition and sequence: The amino acid composition is the
percentage of the constituent amino acids in a particular protein while the
sequence is the order in which the amino acids are arranged from N-terminal
to C-terminal.
3. Charge: Each protein has an amino group at one end and a carboxyl group
at the other end as well as numerous amino acid side chains, some of which
are charged. Therefore, each protein carries a net charge.
4. Hydrophobicity: In aqueous solutions, proteins tend to fold so that areas of
the protein with hydrophobic regions are located in internal surfaces next to
each other and away from the polar water molecules of the solution. Polar
groups on the amino acid are called hydrophilic because they will form
hydrogen bonds with water molecules. The number, type and distribution of
non-polar amino acid residues within the protein determine its hydrophobic
character.
5. Solubility: The 3-D structure of a protein affects its solubility properties.
Cytoplasmic proteins have mostly hydrophilic amino acids on their surface
and are therefore water soluble, with more hydrophobic groups located on
the interior of the protein, sheltered from the aqueous environment. In
contrast, proteins that reside in the lipid environment of the cell membrane
have mostly hydrophobic amino acids on their exterior surface and are not
readily soluble in aqueous solutions.
Enzyme inhibitors are the substance which bind with enzymes and decrease their
activity. They are organic or inorganic in nature.
Enzyme inhibitors are broadly classified into three types as follows:
a. Reversible inhibition
b. Irreversible inhibiton
c. Allosteric inhibition
a. Reversible inhibition: inhibitors bind noncovalently with enzymes and this
inhibition can be reversed by removing inhibitors.
b. They are again subdivided into:
1.competitive inhibition
2.Non competitive inhibition
3.Un-competitive inhibiton
Competitive inhibiton:
The inhibitor competes with the substrate for binding site on enzyme( because of
structural similarity) and binds to the active site.
Example: malonate is structural analog of succinate and competitively inhibit the
enzyme succinate dehydrogenase blocking its conversion to fumarate.
This type of inhibition can be overcome by increasing the concentration of
substrate in the system.
Non-competitive inhibition:
Substances that reversibly bind to group such COO, NH3, SH, OH in a site other
than the active site of an enzyme can alter the protein conformation and
inactivate it by changing site. this is referred to as non-competitive inhibition. As
the inhibitor is not acting at the active site, adding more substrate will not
overcome this kind of inhibition and only removal of inhibitor will restore full
enzyme activity.
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6
Explain
hemoglobin
derivatives.
1D17 – BMI201
Example: heavy metal ions(Ag+, Pb2+) inhibit enzymes.
Uncompetitive inhibition:
In uncompetitive inhibition , the inhibitor binds only to ES complex at locations
other thanthe catalytic site. substrate bibding modifies enzyme structure making
inhibitor binding site available. Inhibition occurs since enzyme substrate inhibitor
complex (ESI) cannot form product. Uncompetitive inhibition can’t be overcome
by adding excess substrate. The inhibitor lowers the concentration of the
functional enzyme.
IRREVERSIBLE inhibition: Inhibitor inactivates the enzymes by binding covalently
with the enzymes, which is reversible. Inhibitors are usually toxic substances.
Example: Iodoacetate
Allosteric inhibition: Enzymes have additional sites known as allosteric sites
besides the active site. such enzymes are known as allosteric enzymes. Enzyme
activity increases when positive allosteric effector binds allosteric site and
decreases with negative allosteric effector binds.
a.
Oxyhemoglobin: present in the RBC, in the body . it is dard red in color and
the lambda max is 577nm
b. Carboxy Hemoglobin: the binding of carbonmonoxide with hemoglobin forms
carboxy hemoglobin. CO binds with the iron atom inthe same way as oxygen
binds. CO has more affinity to Hb than oxygen
c. Methhemoglobin: the substitution of tyrosine for the histidine of the alpha
and beta chains of Hb locks the heme iron into a trivalent state or the action
of oxidizing agents on ferrous form of hemoglobin converts ferrous into ferric
astate. This ferric form cannot bind oxygen and hence oxygen transport is
disturbed. Increased methemoglobin level in the blood is known as
methemoglobinemia
d. Sulfhemoglobin : this is an abnormal sulfur containing Hb attached to the
porphyrin ring. It does not act as an oxygen crrier and it is not present in the
normal red blood cells. It is formed by the toxic action of drugs and chemical
agents that contain sulphur. Sulfhemoglobinemia is characterized by
cyanosis. Unlike methemoglobin cannot be converted to hemoglobin. Thus
once sulfhemoglobinemia occurs it will persist until the erythrocytes carrying
the abnormal pigment reach the end of their life span.
e. Cyanomethemoglobin : hemoglobin is converted t cyanmethemoglobin by
Drabkins reagent . it is a complex formed by methemoglobin with cyanide
and it is a stable compound having lambamax at 540 nm. This provides an
accurate method for the estimation of Hb in the blood.
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