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Biological techniques

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Structures and functions of biological molecules Task 1 Describe the structures and list the functions of the following biological molecules of: a) DNA b) RNA-include types of c) Carbohydrates d) Proteins e) Lipids DNA-DNA contains the genetic information that codes for the RNA and proteins necessary for cell function. All DNA in the chromosomes has to be copied (replicated) and transmitted to daughter cells via mitosis. Structure of DNA Four nucleotides (A,T,C,G) are chemically joined through sugar and phosphate molecules in the backbone. Base pairs across the double helix are joined by complementary base-pairing: A base pairs with T, C base pairs with G. The complementary base pairs direct the addition of nucleotides during synthesis of new DNA strands or synthesis of mRNA (where U is used instead of T) or hybridization of two different molecules. The overall directionality (seen best by looking at the sugar molecules) is antiparallel in the two strands. One strand has a 5'-3' direction; the other a 3'-5' direction. This has consequences for enzymes that work on the DNA (e.g. DNA polymerase, restriction enzymes). RNA RNA-there are three main kinds of ribonucleic acid, each of which has a specific job to do. Ribosomal RNAs-exist outside the nucleus in the cytoplasm of a cell in structures called ribosomes. Ribosome's are small, granular structures where protein synthesis takes place. ...read more.


* The transport of materials in body fluids depends of proteins. * The receptors for hormones and other signalling molecules are proteins. * Proteins are an essential nutrient for heterotrophs. * The transcription factors that turn genes on and off to guide the differentiation of the cell and its later responsiveness to signals reaching it are proteins. * allow for communication with individual cells * transport numerous substances through cells and the blood. * and many more - proteins are truly the physical basis of life. Lipids- Lipids are fats. Their primary purpose in the body is energy storage- a very small mass of lipids can store a very large amount of energy, Describe using examples the laboratory techniques which enable the above biological molecules (a-e) to be identified and characterised Carbohydrate tests Test for Reagent Positive test Carbohydrates - starch Dilute iodine Turns blue-black Carbohydrates - glucose Benedict's solution Orange/red precipitate Carbohydrates - sucrose A few drops of dilute HCl acid + a few drops of Benedict's solution Orange/red precipitate If a chemist is given an unknown sample, he can use a number of chemicals tests to determine if the sample contains a carbohydrate. If it does contain a carbohydrate, further tests can be performed to classify and possibly to identify it. ...read more.


Protein tests Proteins are the most complex and functionally diverse molecules of living organisms. Proteins compose enzymes; blood cells and muscle tissue just to name a few and are therefore associated with meat products. Proteins are created by RNA during DNA Transcription and Translation, a process you will learn about in a later lab. The base elements of proteins are C, H, O and N. The monomers of proteins are 20 different amino acids. The amino acids are bonded together in unique combinations to create a polypeptide chain, the protein polymer. This chain is then folded into a unique, functional protein. Test for Reagent Positive test Protein Biuret test - add a few drops of dilute copper sulphate solution, followed by a few drops of sodium hydroxide Purple or violet precipitate Fat Rub a food sample onto a piece of paper. Leave to dry. Translucent stain round the sample when held up to the light Protein (biruet test). To about 2 cm� of test solution, an equal amount of volume of biuret solution is added down the side of the test tube. A blue ring forms at the surface of the solution, which disappears on shaking, and the solution turns lilac-purple, indicating protein. The colour is due to a complex between nitrogen atoms in the peptide chain and Cu2+ ions, so this is really a test for peptide bonds. ...read more.

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