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Publisher: Jitendar P Vij Publishing Director: Tarun Duneja Editor: Richa Saxena Cover Design: Seema Dogra Textbook of Medical Biochemistry First Edition. EIGHTH EDITION Textbook of V* MEDICAL BIOCHEMISTRY MN Chatterjea Design: Seema Dogra Textbook of Medical Biochemistry First Edition: 1 Textbook of Medical Biochemistry (8th Ed.) - Ebook download as PDF File .pdf), Text File .txt) or read book online. MN chatterjee Biochemistry.

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Ex-Professor and Head of the Department of Biochemistry. Armed Forces . and Dr Rana Shinde in their Textbook of Medical Biochemistry”. Authors' sincere. Medical biochemistry textbook by MN Chatterjea 8th edition. Textbook of Medical Biochemistry Eighth Edition Dr (Brig) MN Chatterjea i was searching for this book for ages online. there are many pdf files but none had. This book titled “Biochemistry” contains a selection of chapters focused on the biochemistry, enzymology, molecular biology and genetics many of which are.

Eu-true and karyon-nucleus include the protists. Essential differences between prokaryotic and eukaryotic cells Prokaryotic cell Eukaryotic cell 1. Cytoplasm contains no cell organelles 8.

Enzymes of energy metabolism bound to membrane 9. Mitochondria absent. No nuclei 7. Cytoskeleton—absent Several different types present Lipid bilayer membrane with proteins Aerobic Nucleus well defined.

Cell division usually by fission. Not well defined nucleus. Anaerobic or aerobic 5. Ribosomes present free in cytoplasm 3. Enzymes of energy metabolism are located in mitochondria Golgi apparatus present—flattened single membrane vesicles Lysosomes present—single membrane vesicle containing packets of hydrolytic enzymes Cell division—by mitosis Cytoskeleton—present RNA synthesised and processed in nucleus. RNA and protein synthesis in same compartment Schematic representation of an eukaryotic cell with cell organelles radiant energy to chemical energy is the highly structural chloroplasts.

Examples are bacteria. Proteins synthesised in cytoplasm Examples: Lysosomes—absent Golgi apparatus absent. Single membrane. Essential differences of prokaryotic and eukaryotic cells are given in Table 1. Storage granules with polysaccharides Mainly unicellular 1. Structure and Functions The mitochondrion is bounded by two concentric membranes that have markedly different properties and biological functions. These are embedded in the nuclear envelope. They vary greatly in size. The shape of mitochondrion is not static.

Transcription is the first step in the expression of genetic information and is the major metabolic activity of the nucleus.

Nucleoplasm of nucleus contain various enzymes such as DNA polymerases. Chemistry and Functions. Mitochondria assume many different shapes under different metabolic conditions.

A mitochondrion—shows half split to show the inner membrane with cristae 5 2. The number of mitochondria in a cell varies dramatically. A double membrane structure called the nuclear envelope separates the nucleus from the cytosol.

Mitochondrial Membranes a Outer mitochondrial membrane: The outer mitochondrial membrane consists mostly of phospholipids and contains a considerable amount of cholesterol. Cell Organelles Eukaryotic cells contain many membrane-bound organelles that carryout specific cellular processes. These complex structures control the movement of proteins and the nucleic acid ribonucleic acids RNAs across the nuclear envelope.

Some algae contain only one mitochondrion. Mitochondrion is the power house of cell Figs 1. The outer membrane also contains many copies of the protein called Porin. A typical mammalian mitochondrion has a diameter of 0.

A mammalian liver cell contains from to mitochondria. Chief organelles and their functions are as follows: A second dense mass closely associated with the inner nuclear envelope is called nucleolus. DNA in the nucleus is coiled into a dense mass called chromatin. In the respiring state. Functional changes: It is now known that mitochondria undergo dramatic changes when they switch over from resting state to a respiring state.

In contrast to outer membrane. H2 reduced FAD produced in the reactions of glycolysis. Varying in shape. The region enclosed by the inner membrane is known as the mitochondrial matrix. Composition of matrix: The enzymes responsible for citric acid cycle and fatty acid oxidation are located in the matrix. It contains high proportion of the phospholipid cardiolipin. Further mitochondrial DNA can be damaged by free radicals. Table 1. These membranes and the aqueous channels they enclose are called cisternae.

The inner mitochondrial membrane is very rich in proteins and the ratio of lipid to proteins is only 0. Since the outer membrane is freely permeable to small molecules. Enzymes of electron transport and oxidative phosphorylation are also located in different areas of this cell organelle. The inner mitochondrial membrane is highly folded.

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The energy produced is trapped and stored as ATP. The space between the outer and inner membranes is known as the intermembrane space. The mitochondrion is not. The matrix also contains several strands of circular DNA. These substances enter the mitochondrion only through the mediation of specific transport proteins.

Endoplasmic reticulum ER: Eukaryotic cells are characterised by several membrane complexes that are interconnected by separate organelles. These organelles are involved in protein synthesis. Recent evidence suggests strongly that the complex serves as a unique sorting device that receives newly synthesized proteins. It is interesting to note that those proteins with no signal or transit peptides regions are rejected by the Golgi apparatus without processing it further and remain as cytoplasmic protein.

Acid phosphatase is used as a marker enzyme for this organelle. Lysosomes are cell organelles found in cells which contain packet of enzymes. These proteins are inserted through the ER membrane into the lumen of the cisternae where they are modified and transported through the cell.

The lysosomal enzymes have an optimal pH around 5. Cytochrome P which participates in drug hydroxylation reside in the ER. The enzymes are active at postmortem autolysis. They do not have attached ribosomes. Lipid hydrolysing enzymes 4.

Phospholipids PL and the enzymes involved in detoxification of drugs. The ER is usually closely associated with the Golgi complexes. Discovered and described for the first time as a new organelle by the Belgian Biochemist de Duve in Near the nucleus. Functions i On the proximal or cis side. These secretory vesicles move to and fuse with the plasma membrane where the contents may be expelled by a process called exocytosis.

Each eukaryotic cell contains a unique stack of smooth surfaced compartments or cisternae that make up the Golgi complex. They can be grouped as follows: Lysosomal Enzymes 1.

Smooth endoplasmic reticulum is involved: A number of important enzymes are associated with the endoplasmic reticulum of mammalian liver cells.

Enzyme Groups Present in Lysosomes Essentially the enzymes about 30 to Proteolytic enzymes 2. Acid phosphatase Catalase. But when the membrane is ruptured. Golgi complexes or Golgi apparatus: They are also called Dictyosomes. They are coated with ribosomes. Functions a Function of rough ER: Rough ER synthesises membrane lipids. These include the enzymes responsible for the synthesis of sterol. Lysosome word derived from Greek word Gree. Nucleic acid hydrolysing enzymes 3. They are surrounded by a lipoprotein membrane.

Carbohydrate splitting enzymes 5. There are two kinds of endoplasmic reticulum ER: Mean diameter is approximately 0. The Golgi complex has a Proximal or Cis compartment. Studies now support the idea that this compartment contains actually a complex network of fine structures called a microtubules.

Allergic responses and arthritic conditions: Released enzymes from ruptured lysosomal membrane can hydrolyse external biopolymers substrates leading to tissue damage in many types of allergic responses and arthritic conditions.

Hence they can not be targeted to lysosomes. The structures are made primarily by the selfassembly of the heterodimer. These crystals when phagocytosed cause physical damage to lysosomes and release of enzymes producing inflammation and arthritis. They are long unbranched slender cylindrical structures with an average diameter of about 25 nm. Inherited disorders: A number of hereditary diseases involving the abnormal accumulation of complex lipids or polysaccharides in cells of the afflicted individual have now been traced to the absence of key acid hydrolases in the lysosomes of these individuals.

Cultured cells from patients with I-cell disease found to be deficient in the enzyme GlcNAc phosphotransferase. Sequence of events in genesis of I-cell disease: Hence these enzymes lack MannoseP the marker and are secreted into plasma leading to high plasma level. Studies have shown that lysosomal enzymes from patients with I-cell disease lack a recognition marker. For many years. In Gout: Urate crystals are deposited around joints.

I-Cell disease: I-cell disease is a rare condition in which lysosomes lack all of the normal lysosomal enzymes. Peroxisomes are small organelles also called Microbodies. The lysosomes thus accumulate many different types of undegraded molecules forming inclusion bodies.

These subcellular respiratory organelles have no energy-coupled electron transport systems and are probably formed by budding from smooth endoplasmic reticulum ER. The particles are approximately 0. Function It is not yet clearly understood and established fully whether or not soluble enzymes are associated or clustered with these structures to form unstable multienzyme complexes.

They are more slender cylinder like structures made up of the contractile protein actin. They are linked to the inner face of the plasma membrane. Lipid metabolismFA synthesis. TCA cycle. The actual physio- 9 chemical state of cytosol is poorly understood. It has a high protein contents.

Power house of the cell. Cytosol also contains free ribosomes often in the polysome form. They appear to be very fragile tubes that form a transient network in the cytosol.

Cytoplasm Cytosol This is the simplest structure of the cell. Maturation of synthesised proteins. Degradation of proteins carbohydrates. Many metabolic reactions take place in cytosol where substrates and cofactors interact with various enzymes. A major role of cytosol is to support synthesis of proteins on the rough endoplasmic reticulum by supplying cofactors and energy. Organelles free sap is called as cytosol.

Involved in protein synthesis.

Function These structures may be involved in the generation of forces for internal cell motion. HMP shunt.

There is no specific structure for cytosol. They exist as 2 subunits and act as the site of protein synthesis. Biogenesis of proteins. DNA replication and transcription. Ankyrin and Band 4. Exocytosis 2. Learn how lipid bilayer is formed B. All membrane carbohydrate is covalently attached to proteins or lipids. Such a membrane barrier that separates cellular contents from the environment is an absolute necessity for life. Learn about proteins present and types: Active transport—Learn about uniport system.

Each internal membrane system is specialised to assist in the function of organelle it surrounds. It separates the cell contents from the outer environment. Learn about nature of carbohydrates 4. Learn about i Phagocytosis ii Pinocytosis—Mechanism of receptor mediated absorptive pinocytosis 3.

Facilitated diffusion 3. The relative content of these components varies widely from one type of membrane to another. Eukaryotic cells contain many internal membrane system that surround the cell organelles.

Learn the chemical composition of the membrane—Lipids and its types. Peripheral proteins: They also contain molecules at their surfaces that provide for cellular recognition and communication. Learn about special structural characteristics of red cell membrane 1. Passive or simple diffusion 2. The plasma membrane. Table 2. Integral protein: Plasma membranes have selective permeability that mediate the flow of molecules and ions into and out of the cell.

Study the fluid mosaic model structure of membrane and additional structures—Lipid rafts and caveolae C. Chemical Composition of the Membranes Membranes are composed of lipids. The degree of unsaturation determines the fluidity of the membranes. Sphingoserine myelin 12 20 20 25 19 17 7 3 2 0 4 6 12 2 4 3 5 7 Glycolipid 10 0 0 0 0 29 Types of Lipids Present in Biomembranes 1. Cephalin Phosphatidyl. About 6 per cent of the membrane lipids of grey matter cells in the brain are gangliosides.

Oleic acid is the most abundant unsaturated fatty acid in animal membrane lipids. The nonpolar tails of most membrane lipids are long chain fatty acids attached to polar head groups. Cholesterol is another common component of the biomembranes of animals but not of plants and prokaryotes. The most common saturated fatty acid groups in membrane lipids in animals contain 16 to 18 carbon atoms.

Composition of different membranes: Content of lipid.

Fatty acids: They are major components of most membrane lipids. There are three types of sphingolipids sphingomyelin. About 50 per cent of the fatty acid groups are saturated. Basic lipid structure—polar head and nonpolar tails 4. They comprise another group of lipids found in biological membranes specially in the tissues of nervous system. Refer to chapter on Chemistry of Lipids for details of lipids. Phosphatidylethanol amine cephalin. The other half of fatty acid molecules contain one or more double bonds.

Structure and Function. Lipids are the basic structural components of cell membranes. They are another group of major components of biomembranes. Hence they are amphipathic Fig.

These proteins can serve as receptors for hormones. Main types of membrane proteins are Fig. Fluid Mosaic Model of Membrane Structure The fluid mosaic model of membrane structure proposed by Singer and Nicholson in is now accepted widely. They can be removed without disrupting the membrane. The carbohydrate chains of many glycoproteins show structural variation from one molecule to another.

They may also interact with integral membrane proteins. Cholesterol helps to regulate fluidity of animal membranes. Early evidences for the model point to rapid and random redistribution of species—specific integral proteins in the plasma membrane of an interspecies hybrid cell formed by the artificially induced fusion of two different parent cells.

Carbohydrates are also present in apoprotein B of plasma lipoproteins. Thus portions of these proteins are in Van der Waals contact with the hydrophobic region of the membrane. A lipid bilayer can form only when the cross-sectional areas of the hydrophobic tail and hydrophilic polar head are about equal.

The hydrophobic effect and the solvent entropy provide the driving force for the formation of lipid bilayer. Occurs in cell membranes and in Lipoproteins. Glycerophospholipids and sphingolipids fulfil this criteria and hence can form bilayer.

The membrane proteins. Not all lipids can form bilayers. This diffusion within the plane of the membrane is termed translational diffusion. Within the plane of the membrane.

Lipid bilayer. A lipid bilayer is about 6 nm across and this is so thin that it may be regarded as a two-dimensional fluid. Approximately 5 per cent of the weight of cell membranes is carbohydrate.

Integral membrane proteins also called intrinsic membrane proteins: These proteins are deeply embedded in the membrane. It has amino acid residues and spans the lipid membrane.

Glycophorin is a major integral membrane glycoprotein of human erythrocytes. Formation of Lipid Bilayer Membrane glycerophospholipids and sphingolipids spontaneously form bilayers. Carbohydrate chains are attached to the amino terminal portion outside the external surface. Their presence on the outer surface of the plasma membrane. Lipid molecules in a bilayer are highly oriented Fig. The lysophospholipids have only one fatty acyl group.

Transmembrane proteins: Some of the integral proteins span the whole breadth of the membrane and are called as transmembrane proteins. The hydrophobic side chains of the amino acids are embedded in the hydrophobic central core of the membrane. It can be quite rapid for a phospholipid molecule. The phase changes. Peripheral membrane proteins also called extrinsic proteins: It has subsequently been shown that it is not only the integral proteins.

It can be compared like icebergs floating in sea water Figs 2. The longer and more saturated fatty acid chains interact more strongly with each other via their longer hydrocarbon chains and thus cause higher values of Tm. Effects of Fluidity of Membrane The fluidity of membrane significantly affects its functions: They also take part in signal transduction. Proteins detected in caveolae include various components of the signal transduction system. Proteins in fluid bilayer Effect of temperature: In a lipid bilayer.

On the other hand. The following two structures which currently drawn attention are: They are dynamic areas of the exoplasmic leaflet of the lipid bilayers enriched in cholesterol and sphingolipids. Many of the caveolae contain a special protein called caveolin By electron microscope they look like flask-shaped indentations of the cell membranes.

The temperature at which the structure undergoes the transition from ordered to disordered state. They are probably derived from lipid rafts. They are involved in signal transduction and possibly other processes. This exchange occurs by way of a channel in bandprotein. It is dimeric having molecular weight of Bandprotein time. The oligosaccharides bound to glycophorin are linked to serine. The inner face of the red blood cells membrane is laced with a network of proteins called cytoskeletons that stabilises the membrane and is responsible for the biconcave shape of the cells: The special peripheral membrane proteins participate in this stability of red cells are: The polypeptide chain of glycophorin contains amino acid residues.

It is another major integral protein found in red cell membrane. Both the C and N terminals of bandprotein are on the cytosolic side of the membrane. Spectrin dimers are linked through short chains of actin molecules and band 4. Integral proteins: Two major integral proteins are found in red cells membrane. Thus bandprotein is an example of a membrane transport protein. Glycophorins are glycoproteins. A sequence of 23 hydrophobic amino acid residues lies within the nonpolar hydrocarbon phase of the phospholipid bilayer.

The nature and function of these proteins require special mention. In red blood cells and other nonmuscle cells. The polypeptide chain of the dimer is thought to traverse the membrane about a dozen Fig. As red blood cells flow through the capillaries of the lungs. The N-terminal residues extend into the cytosol and interact with components of the cytoskeleton.

Bandprotein plays an important role in the function of red blood cells. About 20 actin molecules polymerise to form short actin filaments. Glycophorin integral protein Fig. It contains 60 per cent carbohydrates by weight. Ligand gated channels: In this a specific molecule binds to a receptor and opens the channel. About five distinct types of aquaporins have been recognised. In hereditary spherocytosis the red cells are spherical and in hereditary elliptocytosis they are ellipsoidal.

It is now known that the protein network can also be bound directly to glycophorin integral protein or to bandprotein. These compounds must enter or leave the cells in an orderly manner for normal functioning of the cell.

These compounds include a vast array of substances like sugars. It is a complex of five subunits. Mutations of genes encoding transmembrane proteins can cause specific diseases.

Cation conductive channels are negatively charged within the channel and have an average diameter of about 5 to 8 nm. These defects in shape of red blood cells lead to increased haemolysis.

They mediate and regulate the passage of ions and small molecules upto to mol wt. They result from mutations in the genes coding for proteins of the membrane. They are primarily composed of protein. The abnormality may be from defective spectrin that is unable to bind either ankyrin or band 4. The protein has 2 domains: One binds to spectrin.

Types of Gates Two types of gated channels. These abnormally shaped red blood cells are fragile and have shorter life than normal erythrocytes. Two main types of gates: Ligand-gated and voltage gated.

All ion channels are basically made up of transmembrane subunits that come together to form a central pore through which ions pass selectively. Ion Channels Ion channels are transmembrane channels. The network of spectrin. All channels have gates. These ionophores contain hydrophilic centres that bind specific ions and are surrounded by peripheral hydrophobic regions.

Acetylcholine receptor is present in postsynaptic membrane. Voltage gated channels: These channels open or close in response to changes in membrane potential.

The network of proteins is instead attached to another peripheral protein called ankyrin. Water Channels Aquaporins In certain cells. Transport Systems An essential role of biomembranes is to allow movement of all compounds necessary for the normal function of a cell across the membrane barrier. Gap Junction Certain cells develop specialised regions on their membranes for intercellular communications which are in close proximity.

Highly selective. Acetylcholine released from the presynaptic region binds with the binding site of postsynaptic region. Ionophores Certain microorganisms can synthesise small organic molecules.

Two types: Like valinomycin Refer uncouplers of oxidative phosphorylation. Ankyrin has a molecular weight Activities are affected by certain drugs. Like gramicidin. But it differs from passive diffusion in that it requires a carrier or transport protein. Types of transport system: Transport systems can be classified as follows: D-fructose is absorbed from intestine by facilitated diffusion. Glucose transporters in various cells.

Co-transport system: Increased temperature will increase particle motion and thus increase the frequency of collisions between external particles and the membrane.

Solutes move toward the solution that has the opposite charge. The process does not require any energy and can operate bidirectionally.

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The process neither requires any carrier protein nor energy. Factors affecting net diffusion: The solutes move from high to low concentration. Transport of two different molecules or ions in same direction. Transport of Macromolecules The mechanism of transport of macromolecules such as proteins.

Hence it requires energy. Chloride and bicarbonate ion exchange in lungs in red blood cells. The solute passes from higher concentration to lower concentration till equilibrium is reached. Mechanism of facilitated diffusion has been explained by ping-pong model. It requires the mediation of specific carrier or transport proteins. It operates unidirectionally. Net diffusion also depends on the permeability coefficient for the membrane.

Increased pressure will increase the rate and force of the collision between the molecules. It is a type of cotransport system in which two solutes or ions are transported simultaneously in opposite directions. Active transport occurs against a concentration gradient and electrical gradient.

Initial rate v at which a solute s diffuses across a phospholipid bilayer is directly proportional to the concentration gradient across the membrane [s] out — [s] in and inversely proportional to the thickness t of the membrane. The inside of the cell usually has a negative charge. Hence the rate of diffusion is faster than simple diffusion. Types of Transport Mechanisms The following are three important mechanisms for transport of various compounds across the bio-membrane a Passive or simple diffusion b Facilitated diffusion and c Active transport a Passive or simple diffusion: It depends on the concentration gradient of a particular substance across the membrane.

Uniport system: This system involves the transport of a single solute molecule through the membrane. It is similar to passive diffusion in that solutes move along the concentration gradient. It is a co-transport system in which the transporter carries the two solutes in the same direction across the membrane.

About 40 per cent of the total energy requirement in a cell is utilised for active transport system. Exocytosis Fig. All eukaryotic cells are continuously ingesting parts of their plasma membrane.

This process is also involved in membrane remodelling when the components synthesised in the Golgi apparatus are carried in vesicles to the plasma membrane. The vesicle then pinches off as the fusion of plasma membranes seal the neck of the vesicle at the original site of invagination. Endocytosis Fig. Exocytosis—involves the contact of two inside surface cytoplasmic side monolayers Types of macromolecules released by exocytosis: They fall into 3 categories.

Endocytosis—results from the contact of two outer surfaces monolayers Fig. Most cells release macromolecules to the exterior by the process called exocytosis. The movement of the vesicle is carried out by cytoplasmic contractile elements in the microtubular system.

The process is also called reverse pinocytosis. Types of endocytosis: The endocytosis is of following types: Most endocytic vesicles fuse with primary lysosomes to form secondary lysosomes which contain hydrolyic enzymes. Endocytic vesicles are formed when segments of plasma membrane invaginates enclosing a minute volume of extracellular fluid ECF and its contents.

Vesicular contents are digested liberating simple sugars. Transport of two different molecules or ions in opposite direction 1. Factors required for endocytosis: Endocytosis requires the following: Usually derived from ATP hydrolysis. The innermembrane of the vesicle fuses with the outer plasma membrane. The vesicle fuses with other membrane structures and thus transports of its contents to other cellular compartments.

The protein dynamin which binds and hydrolyses GTP. The granulomas are formed as attempts to wall off bacteria that have not been killed due to genetic deficiencies in the NADPH oxidase system Fig. The formation of these vesicles is an extremely active process. They extend pseudopodia and surround the particles to form phagosomes which later fuse with lysosomes to form Phagolysosomes in which the particles are digested.

By coated vesicles and endosomes All eukaryotic cells have transient structures like coated vesicles and endosomes that are involved in the transport of macromolecules from the exterior of the cells to its interior. It is a property of all cells and leads to the cellular uptake of fluid and fluid contents. Cell surfaces are rich in receptor proteins that can combine with macromolecules ligands.

Phagocytosis Greek word-Phagein-to eat is the engulfment of large particles like viruses. Macrophages are extremely active and may ingest 25 per cent of their volume per hour. These coated pits are rapidly pinched off and are internalised as coated vesicles.

The coated vesicles about nm in diameter have a very characteristic brittle coat on their outer surface. Sequence of events that occur in chronic granulomatous disease Defect: The disorder is attributed to mutations in the genes encoding the four polypeptides that constitute the active NADPH oxidase system.

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In resting phagocyte it is in an inactive form. The disease is characterised by: Killing of bacteria within phagolysosomes appears to depend on the combined action of elevated pH. The NADPH oxidase system is activated by recruitment in plasma membrane by two more cytoplasmic polypeptides. The vesicles are covered with an unusual peripheral protein called clathrin. Biochemical mechanism is called respiratory burst.

Approximately 2 per cent of the external surface of plasma membrane are covered with receptors and characteristic coated pits. In such a process. It is a nonselective process in which uptake of a solute by formation of small vesicles is simply proportionate to its concentration in the surrounding extracellular fluid ECF.

It is bad. The low pH breaks the linkage between receptor-macromolecule. Efforts are in progress to use gene therapy to restore the activity of CFTR protein. Genetic mutation produces an abnormal CFTR. The commonest mutation found involves deletion of three bases resulting to loss of phenylalanine in position. They do not contain hydrolytic enzymes. The low density lipoproteins LDL molecule bound to receptors are internalised by means of coated pits.

Clinical Features: The macromolecules containing endosomes now move. The internalised coated vesicles fuse with the endosomes and discharge their macromolecules into the interior of the endosomes. Gene for CFTR has been identified on chromosome 7.

Iron toxicity also occurs with excessive uptake due to endocytosis. Cystic Fibrosis Inheritence: A recessive genetic disorder. This gene is responsible for encoding CFTR protein.

Glycogen animal starch —Chemistry and properties. Carbohydrates are defined chemically as aldehyde or ketone derivatives of the higher polyhydric alcohols.

Carbohydrates are divided into four major groups— monosaccharides. List the disaccharides of biological importance and learn their properties. Example—Mucopolysaccharides glycosaminoglycans 1. Differentiate sucrose from either lactose or maltose.

List the monosaccharides of biological importance and learn their properties. Learn the general properties of carbohydrates with reference to glucose. Chemistry and properties. List and describe the monosaccharides of biological importance.

Specific Objectives A. Sulphate free acid MPS—Hyaluronic acid and chondroitin 2. Define carbohydrates in chemical terms. Study important properties of monosaccharides. Describe the biomedical importance of carbohydrates. Homopolysaccharides homoglycans 1. List the disaccharides of biological importance. Neutral MPS—Blood group substances. Example of both aldoderivatives and ketoderivatives.

Study the chemistry and properties of various polysaccharides. What are carbohydrates? Their general properties and biomedical importance. Learn chemistry and functions of proteoglycans. Differentiate between amylose and amylopectin in tabular form 2. Classify carbohydrates into four major groups with examples of each group. Learn chemistry of each MPS. Study the chemistry and functions of proteoglycans. Study the chemistry and properties of three important disaccharides.

Study the sugar derivatives of biological importance. Use of dextran as plasma expander. Heteropolysaccharides heteroglycans. Learn about lactalose. Relation of MPS to mucopolysaccharidoses. Dextrins and Dextran—Differentiate. Learn the chemistry and properties of polysaccharides of biological importance.

Inulin—Chemistry and physiological importance. General Properties in Reference to Glucose Asymmetric carbon: A carbon atom to which four different atoms or groups of atoms are attached is said to be asymmetric Fig. Those sugars which yield 3 to 10 monosaccharide units on hydrolysis. Constituents of compound lipids and conjugated proteins. General formula: CnH2nOn They can be subdivided further: C-atom 5 in glucose determines the series.

The presence of asymmetric carbon atoms in a compound gives rise to the formation of isomers of that compound. Heteropolysaccharides heteroglycans: Polymer of different monosaccharide units or their derivatives. Inherited deficiency of certain enzymes in metabolic pathways of different carbohydrates can cause diseases. Constituents of mucopolysaccharides which form the ground substance of mesenchymal tissues.

Most of the monosaccharides occurring in mammals are D-sugars.

Example—Mucopolysaccharides glycosaminoglycans. Polysaccharides Glycans: Those sugars which yield more than ten molecules of monosaccharides on hydrolysis. Homopolysaccharides homoglycans: Polymer of same monosaccharide units. Such compounds which are identical in composition and differs only in spatial configuration are called stereoisomers.

Degradation products utilised for synthesis of other substances such as fatty acids. D-Series and L-Series: The orientation of the H and OH groups around the carbon atom just adjacent to the terminal primary alcohol carbon. Those sugars which yield two molecules of the same or different molecules of monosaccharide on hydrolysis. Lactose principal sugar of milk—in lactating mammary gland.

Derangement of glucose metabolism is seen in diabetes mellitus. When the — OH group on this carbon is on the right. C6H10O5 n Polysaccharides are further divided into two groups: The number of possible isomers of any given compound depends upon the number of asymmetric carbon atoms the molecule possesses.

Stereoisomers of glucose As the two reacting groups aldehyde and alcoholic group belong to the same molecule. Compounds related in this way are called anomers and carbon When an aldohexose is first dissolved in water and the solution is put in optical path so that plane polarized light is passed. Such a mixture is said to be Racemic.

The mechanism of mutarotation probably involves opening of the hemiacetal ring to form traces of the aldehyde form. Chemistry of Carbohydrates 25 has no optical activity.

When a beam of plane-polarised light is passed through a solution exhibiting optical activity. When the OH group extends to right. Anomers and anomeric carbon: This phenomenon of change of rotation is called as mutarotation. When equal amounts of dextrorotatory and laevorotatory isomers are present. The separation of optically active isomers from a racemic mixture is called resolution.

If the open-chain form of D-Glucose. Presence of asymmetric carbon atoms also confers optical activity on the compound. The two cyclic compounds. He prepared two isomeric forms of DGlucose by crystallisation under different conditions: Process by which one epimer is converted to other is called epimerisation and it requires the enzyme epimerase. The aldehyde form is extremely unstable and exists only as a transient intermediate.

Haworth projection. Pyranose and furanose forms of glucose in solution a Trioses: Both D-glyceraldehyde and dihydroxyacetone occur in the form of phosphate esters. Similarly Haworth designated sugar containing 5-membered rings as the furanoses. Haworth in suggested that the six-membered ring forms of the sugars be called Pyranoses. This work of Tanret showed that glucose exists in isomeric forms which in solution changes into the same equilibrium mixture regardless of which form is dissolved.

Recent studies [ 54 — 56 ] continue to reveal triptans complex actions including meta-analyses comparing the effectiveness of triptans alone or in combination with other drugs [ 57 ].

Although triptans are the most effective drugs for migraine they exhibit therapeutic variability in different patient groups. The different levels of drug response can be explained by different metabolic routes, rates and efficiency.

In a meta-analysis by Cameron et al. Triptans used in combination with ASA or acetaminophen, or by alternative administration methods injectables yielded slightly better outcomes than standard dose triptan tablets.

Biochemical peculiarities of the guinea pig and some possible examples of convergent evolution

Thorlund et al. Among the seven different triptans tested, eletriptan was the best triptan and all triptans were found better than placebo [ 58 ]. This result was also upheld by a recent report showing that triptans still have the most favorable efficacy-tolerability profile [ 59 ]. The hunt for better more specific drugs continues particularly in the era of pharmacogenetic research whose goal is to evaluate the impact of genetic constitution on migraine drug response [ 60 ].

Pharmacogenetics recognizes that numerous genes drug metabolizing enzymes and drug transporters play a role in the mechanism of drug response, resistance, toxicity, drug transport or drug targeting and ultimately affect how patients metabolize and consequently respond to different drug regimens [ 61 , 62 ].

This information can help inform doctors prescribing practices ie. In a study by Terazzino et al. However the authors caution some limitations in their study such as a small sample size but nevertheless support future pharmacogenetic testing to identify algorithms for more effective treatment [ 64 ].

Recently, Christensen et al. To explore the role of genetic factors in drug metabolism Gentile et al. Serotonin receptors are also targeted by other drugs besides triptans and in a study by Brandl et al.

In a follow up study in , Gupta et al. Although specific SNPs in genes that metabolize triptans have yet to be identified, current pharmacogenetics studies indicate that defining the effect SNPs have on drug metabolism and treatment response may have value in classifying patients into groups of poor metabolizers to predict therapeutic responses and to evaluate sex differences.

Several studies have shown that SNPs in genes of most metabolic enzymes can affect enzyme activities and may account for inter-individual variation, in drug bioavailability and efficacy and consequently can bear a role in therapy response [ 63 ]. Results of future testing the clinical utility of SNPs and genetic variability in the signalling components of the serotonergic system as well as additional genes involved in triptan metabolism will impact patient care and may be useful to personalize medicine.

Metabolic routes of serotonin Tryptophan - Indole-kynurenine-niacin pathway Tryptophan is a requisite precursor necessary for various metabolic reactions primarily the synthesis of serotonin, proteins, melatonin, tryptamine and kynuramines [ 82 , 83 ]. In the body, tryptophan is metabolized, via two basic pathways, the indole-kynurenine-niacin pathway and the serotonin-melatonin pathway [ 84 ].

Recently Curto et al. Curto et al. Indeed activation or inhibition of kynurenine pathway enzymes and accumulation of kynurenines within the CNS has been considered a therapeutic strategy [ 90 ].

However, the potential of this therapeutic strategy has not yet been tried in migraine [ 91 ]. To investigate central and peripheral serotonin turnover in neurological disorders and in depressed mood, researchers have adopted the tryptophan depletion technique Acute Tryptophan Depletion ATD [ 82 ]. Initial studies in healthy volunteers showed that depletion of tryptophan is correlated with a decline in central serotonin turnover [ 92 , 93 ].

The tryptophan-serotonin relationship has been confirmed in animal models [ 94 — 96 ] and was first demonstrated in , indicating this mechanism may be potentially important in serotonin related pathologies in humans [ 97 , 98 ]. Changes in the composition of the blood plasma in the periphery can influence functioning of the nervous system and affect various serotonin-dependent brain functions and mood states like depression [ 99 — ]. Changes in diet and nutrition can lead to changes in brain levels of the precursors for neurotransmitter synthesis and influence the rates at which neurons synthesize neurotransmitters [ ].

Tryptophan depletion increases nausea, headache and photophobia in migraine sufferers [ ]. Two studies in the 70s, tested L-tryptophan treatment in headache patients and reported headache indices were markedly lower with supplementation of L-tryptophan than with placebo [ , ]. The utility of tryptophan for both research and clinical purposes has been underexplored.

Further analysis of the relationship of plasma tryptophan with brain serotonin metabolism in both normal and diseased states will be beneficial to understanding the complex serotonergic biochemistry of migraine.

Tryptophan - Serotonin-melatonin pathway Melatonin is a hormone that is synthesised at night-time from the precursor tryptophan in the pineal gland.Action with alkalies: Inherited deficiency of certain enzymes in metabolic pathways of different carbohydrates can cause diseases.

Two students record the results of their experiment Course and Program Information. Erythromycin contains dimethyl amino sugar and carbomycin 3-amino-D-Ribose. When an aldohexose is first dissolved in water and the solution is put in optical path so that plane polarized light is passed. Phospholipids PL and the enzymes involved in detoxification of drugs.

These defects in shape of red blood cells lead to increased haemolysis.