Biochemistry

• Carbohydrates are widely distributed in plants and animals and are the most abundant biomolecules on the Earth.
• Carbohydrates are polyhydroxy aldehydes or ketones, or substances that yield such compounds on hydrolysis.
• Many, but not all, carbohydrates have the empirical formula (CH 2 O) n.
• Carbohydrates can be classified based on their size: monosaccharides, disaccharides, oligosaccharides, and polysaccharides.
• Certain carbohydrates (sugar and starch) form dietary staple, and the oxidation of carbohydrates is the central energy-yielding pathway.
• Insoluble carbohydrate polymers serve as structural and protective elements in the cell walls of bacteria and plants and in the connective tissues of animals.
• Other carbohydrate polymers lubricate skeletal joints.
• Specific carbohydrate containing molecules act in cell-cell recognition and adhesion, cell migration during development, blood clotting, the immune response, and wound healing.
• Carbohydrates are simple sugars, consist of a single polyhydroxy aldehyde or ketone unit.
• The most abundant monosaccharide in nature is D-glucose, sometimes referred to as dextrose.
• Monosaccharides of more than four carbons tend to have cyclic structures.
• Monosaccharides are usually colourless, water-soluble, crystalline solids.
• Some monosaccharides have a sweet taste.
• Compounds that have the same chemical formula but have different structures are called isomers.
• Carbohydrate isomers that differ in configuration around only one specific carbon atom are defined as epimers of each other.
• Heparin is a natural anticoagulant made in mast cells (a type of leukocyte) and released into the blood, where it inhibits blood coagulation by binding to the protein antithrombin.
• The oligosaccharide portions of glycoproteins form highly specific sites for recognition and high-affinity binding by other proteins.
• Proteoglycans are macromolecules on the cell surface or extracellular matrix, with Glycosaminoglycan chains joined covalently to a membrane protein or a secreted protein.
• Glycolipids are membrane lipids in which the hydrophilic head groups are oligosaccharides.
• Glycoproteins are found on the outer face of the plasma membrane, in the extracellular matrix, and in the blood, with several oligosaccharides of varying complexity joined covalently to a protein.
• Heparin is a glycoconjugate, which is the biologically active molecule.
• Proteoglycans are major components of connective tissue such as cartilage.
• Glycoproteins are found in specific organelles such as Golgi complexes, secretory granules, and lysosomes.
• Gangliosides are membrane lipids of eukaryotic cells made up of sialic acid and glycosphingolipid, with the oligosaccharide groups on gangliosides helping in cell recognition and cell-to-cell communication.
• The glycosaminoglycan commonly forms the greater part of the proteoglycan molecule and is often the main site of biological activity.
• Lipopolysaccharides are the dominant surface feature of the outer membrane of gram-negative bacteria, with lipopolysaccharides being important targets of the antibodies produced in response to bacterial infection and being important determinants of bacterial strain.
• Many of the proteins secreted by eukaryotic cells are glycoproteins, such as antibodies and hormones like luteinizing hormone, follicle stimulating hormone etc.
• Glucuronic acid/iduronic acid are components of Heparin.
• Another type of isomerism involves a pair of structures that are mirror images of each other, these mirror images are called enantiomers, and they are designated as a D- and an L- sugar.
• The concentration of glucose in the test sample can be extrapolated using the absorbance of the test sample and the standard curve.
• Standard solutions for glucose determination are glucose solutions prepared at different concentrations.
• Copper reduction method (modified Folin-Wu method) is used for the determination of glucose by measuring the absorbance of the sample (test) solution and a set of standard solutions.
• Glycogen molecules contain both alpha 1 - 4 glycosidic bond and alpha 1 - 6 glycosidic bond.
• Proteoglycans are formed when glycosaminoglycans are bound to proteins.
• Oxidation of both the aldehyde and terminal hydroxyl groups produce glucaric acid.
• Amylopectin is a branched chain of glucose molecules joined by only alpha 1 - 6 glycosidic bonds.
• Glycogen is a more extensively branched polysaccharide than starch.
• Amylose is a linear chain of glucose molecules joined by alpha 1 - 4 glycosidic bonds.
• Galactose is a monosaccharide that contains an aldehyde group.
• Fehling's test for qualitative analysis of sugar works on the principle that the reducing sugar will be reduced to enediols.