1 Structure and Function of Large Biological MoleculesCh 3

2 Large Biological MoleculesCritically important molecules in all living things divided into 4 classes: Lipids (fats) Carbohydrates (sugars) Proteins Nucleic Acids (DNA & RNA) Carbs, Proteins and Nucleic Acids are Polymers

3 Polymers are built from MonomersPolymers (large) are made of covalently bonded monomers (building blocks) Polymers built by dehydration synthesis Polymers broken into monomers by hydrolysis The order of the monomer determines the function and shape of the polymer.

4 Hydrolysis & Dehydration synthesisBreaks bonds in a polymer by adding water Dehydration Synthesis Bond forms between 2 monomers & a water molecule is lost Facilitated by enzymes

5 Carbohydrates, fuel & building materialCarbon & water CH2O w/ a 2:1 ratio of H to O Can exist as a ring or linear, notice the numbering of the Carbon atoms. Start at the top of a chain & to the right of a ring.

6 Monosaccharides: simple sugarsMonosaccharides generally have molecular formulas that are some multiple of the unit CH2O. Glucose has the formula C6H12O6. Quick energy for cells Monosaccharides: one ring structure Disaccharides: 2 ring structure Polymer: many rings Most names for sugars end in –ose. Glucose, an aldose, and fructose, a ketose, are structural isomers. Monosaccharides are also classified by the number of carbons in the carbon skeleton

7 Disaccharides Consist of 2 monosaccharides joined by a glycosidic linkage (covalent bond formed by dehydration synthesis) Glucose + fructose= sucrose Glucose + galactose = lactose

8 Polysaccharides Polysaccharides – many saccharidesEnergy storage (alpha glucose) - helical Starch – plants Amylose - unbranched Amylopectan - branched Glycogen – animals, liver and muscle energy stores Structure and support (beta glucose) – straight Cellulose – plants, structural support creates a cable like structure called microfibrils by H-bonding to adjacent cellulose molecules Chitin – exoskeletons and fungi Contains nitrogen

9 Lipids: not a polymer or a macromoleculeLipids are hydrophobic, mostly hydrocarbons with non-polar covalent bonds In a fat, three fatty acids are joined to glycerol = triglyceride Glycerol: an alcohol with 3 carbons each with a hydroxyl group

10 Saturated vs. Unsaturated FatsHave all single bonds between C atoms, solid at room temperature Unsaturated Fats: Have double or triple bonds between C atoms, liquid at room temperature

11 Fats and Cell MembranesIn a phospholipid, two fatty acids and a phosphate group are attached to glycerol: the main component of cell membranes The two fatty acid tails are hydrophobic, but the phosphate group and its attachments form a hydrophilic head

12 Choline Phosphate Hydrophilic head Glycerol Fatty acidsFig. 5-13ab Choline Phosphate Hydrophilic head Glycerol Fatty acids Hydrophobic tails Figure 5.13 The structure of a phospholipid (a) Structural formula (b) Space-filling model

13 Steroids Lipids characterized by a carbon skeleton of 4 fused ringsCholesterol and many other hormones (sex hormones) important in cell membranes Too much builds up in the arteries = atherosclerosis Trans fats: artificially made fats, no enzymes to break them down = heart disease cholesterol

14 Proteins Enzymes – catalysts Structural support Storage TransportCell communication Movement Defense

15 Proteins Protein – made of one or more polypeptidesPolypeptide – polymer of amino acids joined by peptide bonds amino acids are alternately flipped upside down Amino acid – contains an amine group and a carboxyl group 20 different Differ in properties due to R groups or side chains

16 Protein Structure Protein Folding AnimationPrimary: Amino Acid Sequence Secondary: α helix or β pleated sheet (H bonds between a.a.) Tertiary: the folding of the secondary structure 3-D due to hydrogen bonds and disulfide bridges Quaternary: 2 or more polypeptide chains put together by chaperone proteins (errors in folding cause disease: Alzheimer’s and Parkinson’s, sickle cell anemia) Primary Structure Secondary Structure Tertiary Structure Quaternary Structure

17 Fig. 5-22 Normal hemoglobin Sickle-cell hemoglobin Primary structure Primary structure Val His Leu Thr Pro Glu Glu Val His Leu Thr Pro Val Glu 1 2 3 4 5 6 7 1 2 3 4 5 6 7 Exposed hydrophobic region Secondary and tertiary structures Secondary and tertiary structures  subunit  subunit     Quaternary structure Normal hemoglobin (top view) Quaternary structure Sickle-cell hemoglobin     Function Molecules do not associate with one another; each carries oxygen. Function Molecules interact with one another and crystallize into a fiber; capacity to carry oxygen is greatly reduced. Figure 5.22 A single amino acid substitution in a protein causes sickle-cell disease 10 µm 10 µm Red blood cell shape Normal red blood cells are full of individual hemoglobin moledules, each carrying oxygen. Red blood cell shape Fibers of abnormal hemoglobin deform red blood cell into sickle shape.

18 Proteins Denaturation – the unfolding of a proteinDepends on chemical and physical conditions pH, Ionic concentration, temperature Chaperonins – aid in the folding process

19 Nucleic Acids (more in Ch 16)Genes - Store and transmit genetic information and are made of nucleic acids DNA – deoxyribonucleic acid RNA – ribonucleic acid Proteins are made from info in nucleic acids Nucleotides are the monomers of nucleic acids Sugar Ribose Deoxyribose Phosphate Base Purines - AG Pyrimadines - CT Nucleotide DNA replication

20 DNA 1 Synthesis of mRNA in the nucleus mRNA NUCLEUS CYTOPLASM mRNA 2Fig DNA 1 Synthesis of mRNA in the nucleus mRNA NUCLEUS CYTOPLASM mRNA 2 Movement of mRNA into cytoplasm via nuclear pore Ribosome Figure 5.26 DNA → RNA → protein 3 Synthesis of protein Amino acids Polypeptide

21 Graphic Organizer for the large Biological MoleculesNucleic Acid Proteins 4 levels Biological Molecules Carbohydrate Lipids