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Code 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. Page 2 of 3 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. Page 3 of 3