Properties and Functions of Water, Carbohydrates, Proteins, and Lipids, Lecture notes of Genetics

Download Properties and Functions of Water, Carbohydrates, Proteins, and Lipids and more Lecture notes Genetics in PDF only on Docsity! Water - a polar molecule which allows hydrogen bonds between molecules giving water important properties. Property Function Solvent Polar molecules dissolve in water and are able to be transported. Metabolite Water is a reactant in photosynthesis and hydrolysis, produced in aerobic respiration and condensation. High specific heat capacity A lot of energy is required to change the temperature of water so aquatic/cellular environments remain stable. High latent heat of vaporisation Evaporative cooling. Surface tension Support and buoyancy. H H H H O O δ+ δ+ δ+ δ+ δ- δ- Hydrogen bonds Carbohydrates Monosaccharides Triose 3C important in respiration and photosynthesis. Pentose 5C Important in nucleotides. H H H HH C C C O O O2 Hexose 6C Glucose is a really important hexose sugar. It is used in respiration. Monosaccharides are linked to make dimers and polymers. There are two isomers of glucose. H I C I HO 6CH20H I C I H OH I C I H H I C I OH OH O H I 1C I 3 4 2 5 H I C I HO 6CH20H I C I H OH I C I H H I C I OH H O OH I 1C I 3 4 2 5 or α glucose β glucose α−glucose OH group points up on carbon 1 but on β−glucose it points down. Disaccharides Sucrose Glucose and fructose linked in a condensation reaction where one molecule of water is lost and a glycosidic bond is formed. Maltose As above but the monosaccharides linked are α−glucose and α− glucose. Lactose A dimer formed from glucose and galactose. Polysaccharides Starch A polymer of α−glucose (composed of straight-chain amylose and branched amylopectin) Compact energy storage in plants with little osmotic effect. Glycogen A polymer of α−glucose, energy storage in animals. Cellulose A polymer of β−glucose, adjacent monomers twisted through 180° to each other, allowing hydrogen bonds between chains, forming microfibrils. A strong structure for plant cell walls. Chitin As cellulose but with some –OH groups replaced by nitrogen-containing acetylamine groups. Strong, lightweight and waterproof for exoskeletons. OHHOCH2 OH H H HH H 14 3 2 5 O Proteins Proteins are constructed from 20 types of amino acid. The general form of an amino acid is shown here. The R group is different in each of the 20. Two amino acids linked form a dipeptide. A polymer is called a polypeptide. Primary Structure The sequence of amino acids as coded by the DNA. Amino acids are linked together by condensation reactions that form peptide bonds. Secondary Structure Hydrogen bonds formed between the amino acids in the chain cause it to fold into an alpha helix or beta pleated sheet. Tertiary Structure Hydrophobic interactions between the variable groups within the secondary structure forms and disulphide and ionic bonds forms a very specific folded structure e.g. the active site of an enzyme. Quaternary Structure More than one polypeptide chain linked to form a molecule. Fibrous proteins e.g keratin- structural function Globular proteins e.g enzymes- metabolic function Test for proteins Biuret solution -blue Positive reaction – A purple/violet colour is seen. H | N | H R | C | H O || C | OH Variable group Carboxyl (acid) group Amino(basic) group Chemical elements are joined together to form biological compounds