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Transcript
LIPIDS -Fats , oils, Steroids, waxes, Phospholipids. Most common property; Insolubility in water . Hydrophobic in nature. Lipids are not polymers, but a macromolecule Functions: Fats and oils are biological fuels (store energy) Components of membranes. Hormones, fat soluble vitamins, Light absorbing pigments. Fats serve as thermal insulation, waxes on leaf serve as water repellent FATS or SIMPLE FATS. Made up of a. Glycerol b. Fatty acids FATS • Fatty acid -consists of a carboxylic Group and -A long hydrocarbon chain (C4 to C18) -hydrophobic due to hydrocarbon chain FATS, , TRIGLYCERIDE • 3 fatty acid chains linked to a glycerol molecule via an ester linkage called • TRIACYLGLYCEROL OR TRIGLYCERIDE OR FATS . • FATS are esters of Glycerol and fatty acids Saturated fatty Acid No double bonds in C-C skeleton Fat made from saturated fatty acid is called a saturated fat Animal fats are saturated .ex Butter Unsaturated Fatty acid • An unsaturated fatty acid has one or more double bonds • Produce a kink or bending in the structure. • fats of plants and fishes – liquids at room temperature --OILS • Ex: Cod liver oil, Groundnut oil Phospholipids – Phospholipids • Glycerol molecule with… • 2 fatty acid chain AND • A phosphate group – polar or hydrophilic Chapter 7: Membrane structure and function PHOSPHOLIPIDS • Hydrophilic Region:phospholipid head is polar and it is associated with water molecules • Hydrophobic Region : long FATTY ACID TAIL IS nonpolar. Major components of all CELL MEMBRANEs STEROIDS • Steroids consist of carbon skeleton of four fused ring • Different functional groups attached to it Cholesterol • Present in animal membranes • Is the precursor for sex hormones, bile acids High % of cholesterol in blood may cause atherosclerosis. LIPIDS • Compare the structure of a fat ( triglyceride) with that of a phospholipid • How do saturated fats differ from unsaturated fats both in structure and in function • Why are human sex hormones considered to be lipid. PROTEINS Amino acids • Amino acids are the building blocks of proteins. • Proteins are built from a repertoire of 20 amino acids Glycine : Gly Amino acid Central carbon is referred to as α carbon. Linked to 1. Carboxylic acid group (COOH) 2.Amino group (N H2) 3.Hydrogen atom and 4.R is the variable component -the side chain CORN Glycine has H atom Aromatic amino acids Glycine is the smallest a.a. It is the only a.a. which is not having a chiral C atom. The sulfhydryl( -S-H) group of two cysteine can react to form a covalent disulfide bridge(-S-S) -a Cystine molecule The side chain of Proline is covalently linked back to Amino group. • Essential amino acid • -supplied by dietary protein • Try, Lys, Met, Phe, Thr, val, Leu& Iso • Non essential amino acid -synthesis by the body. -ala, asp, cys, Glu, Gly, Pro, ser, Tyr Mnemonic for semiessential and essential a.a. PVT TIM HALL. (Phe, Val, Thr, Trp, Ile, Met, His, Arg, Leu & Lys) What are proteins • Proteins are polymers of amino acids in which the adjacent amino acids are connected by peptide bonds. Peptide Bonds Peptide bonds a C-N covalent bond between the carboxyl group(-COOH) of one amino acid And the Amino( NH2 ) group of an adjacent amino acid Polypeptide Polymer of many amino acids linked by peptide bond. • Each polypeptide has N-terminal and C terminal. Protein • Protein conformation is defined by its sequence of a.a. residues , which determines the function. • 3D- structure of a protein is determined by The characterisitics & interactions of the side chains in it’s a.a. sequence . Protein: glucagon -29 residues Lysozyme - 129 residues mol wt. 13,930 Linus Pauling (February 28, 1901 – August 19, 1994) Structure of chemical bonds & structure of molecules Nobel prize for chemistry Nobel Prize for Peace Explained the structure of alpha helix of proteins Example of Transthyretin Primary Structure C-terminus N-terminus Linear arrangement or sequence of amino acids linked by peptide bond Determined by genetic information Secondary structure a helix • Polypeptide chains fold into regular structures such as the alpha helix, the beta sheet • Hydrogen bonds stabilizes the secondary structures. In alpha Helix • all the main chain - CO and -NH groups are hydrogen bonded. Secondary structure a helix alpha Helix coiled structure stabilized by intrachain hydrogen bonds. • all the main chain - CO and -NH groups are hydrogen bonded. Hydrogen Bonding in H20 O atom H atom A hydrogen bond forms when a hydrogen atom covalently bonded to one Electronegative atom is also attracted to another electronegative atom .In living Cells, the electronegative partners are usually oxygen or nitrogen atoms. Secondary structure • b sheet B Sheet consists of beta strands connected laterally by five or more hydrogen bonds, forming a twisted, pleated sheet Ex :β –keratins in claws, scales , feathers , beaks & silk is made up of beta sheets. Tertiary structure Is the 3D structure of a protein Tertiary structure • Is the 3D structure of a protein • Interactions between the side chains of the amino acids. • Hydrophobic interactions, ionic bond and vanderwaals interactions are involved. Tertiary structure of 6 different proteins Orange color shows ----Beta sheets. Blue color shows alpha helix. Quaternary Structure • Proteins consisting of more than one polypeptide chain display quaternary structure. • Each polypeptide chain is called a subunit. Examples of quaternary structure. Haemoglobin- 4 polypeptide chains 2 alpha ,2betachains -globular protein Collagen-Triple Helix, Proteins • Function as catalysts. • Mechanical support • Immune protection • Interact with other biological macromolecules To form macromolecular assemblies each type of protein has a unique 3Dstructure or conformation Structure determines function Protein Denaturation • Loss of three dimensional structure of the Protein causes loss of biological function. Ex: salt concentration, extremes of pH, thermal energy from heat, organic solvents alcohol or acetone. boiling of egg. Renaturation: certain proteins denatured by heat or denaturing agents regain their native structure Protein folding • Protein folding in cell is assisted by a class of proteins chaperonin. Refer chapter 2 & 3 (Biology- campbell ) polar, nonpolar covalent bond, hydrogen bond , hydrophilic & hydrophobic character . - For understanding the concept ( not in syllabus) BONDING IONIC BONDING COVALENT BONDING non-polar covalent and polar covalent Bonding Covalent bonding Polar covalent bond Bonding Covalent bonding Polar covalent bond – unequal sharing of electrons A great example of a molecule with polar covalent bonds is water. Why is water considered polar? What is a partial positive and partial negative charge? Bonding Covalent bonding Non-polar covalent bond – equal sharing of electrons.hydrophobic Polar covalent bond – unequal sharing of electrons. Hydrophilic. Bonding Ionic bonding – Atoms transfer or accept electrons from one another The sodium ion and the chloride ion will be attracted to each other and form an ionic bond. Na + Cl - The ionic bond is due to the attractive forces between the now positively charged sodium & the negatively charged chloride. Bonding Electronegativity is the tendency of an atom to attract electrons. If the electronegativity of an atom is high, then it attracts and holds on to electrons. If the electronegativity of an atom is low, then it tends to give electrons away.