BCH 380 Biochemistry Exam # 2 Study Guide Lectures: 13 – 21 (Chapters 9-13, 15-18) March 2015Lecture 13 (February 23) Chapter 9: Hemoglobin- What are the 2 Oxygen Carriers in the Body?:1. Hemoglobin: Hemoglobin (Hb) carries O2 from lungs to tissue Hb-O2 and CO2 and H+ from tissues to lungs HB-CO2/H+. Not a true enzyme, but has allosteric behaviors in the regulation of O2 carrying capacity Tetramer (alpha2beta2) Bind 4 O2 Found in RBCs Gives up 66% of O2 Fetal Hb has a higher affinity for O2 than maternal Hb 2. Myoglobin: Monomer Bind I O2 Found only in muscles Gives up 7% of O2-How does oxygen binding to hemoglobin effect kinetic curve and relate to release?o Mb displays classical M-M kinetics (hyperbolic). o Hb displays classical Allosteric Kinetics (sigmoidal).-Where is oxygen bound in heme and how does binding of one oxygen influence structure and cooperative binding of more oxygen?o **Binding of oxygen moves the iron atom into the plane of the heme Low oxygen affinity= T-state  High Oxygen Affinity (O2 bound to heme)= R-state1. 2,3-BPG binds to deoxyhemoglobin= stabilized T-state of O2 carrier2. Molecular symmetry and positive polarity form salt bridges with lysine and histideine residues in the 4 subunits of hemoglobin**Fetal Hb has a higher affinity for O2 than maternal Hb -What are the allosteric regulators (positive and negative) of oxygen affinity in hemoglobin and how do they work? Bohr effect.The Bohr Effect: The effect of pH and CO2 on O2 binding to Hb Increase CO2= Decrease pH= proteins release O2 load Decrease CO2= Increase pH= Hb picks up more O2 CO2 reacts with water to form H2CO3Lecture 14 (February 25) Chapter 10: Carbohydrates -Role and structures of carbohydrates o Single most abundant form of biomolecule found in nature.o Have the general molecular formula of (CH2O)n where n = 3 or higher.o Function: cellularly= forms of energy, structural= linkers with other biomolecules (glycolipids, RNA/DNA, glycoproteins).o Serve as recognition molecules between cell types and cell structures.o Carbs have one or more asymmetric (chiral) centero As the monomer, they can exist in either a linear of cyclized formo They can form polymers via a glycosidic bondo Readily form H-bonds to water or other molecules of importance in their environment-(Nomenclature) aldose? Ketose? Hexose? Triose? etc Numbering.: A sugar that meets the (CH2O)n formula ends in –ose and can be named by number of carbon atoms e.g. triose, tetrose, pentose, hexose.o The name can also include whether it is an aldose or ketose e.g. aldohexose, ketopentose etc,o Monosaccharide: individual sugar unit with formula (CH2O)n. 2 Classes:1. Aldoses: contains analdehyde –at least onechiral center2. Ketoses: has a ketonefunctional group- atleast one chiral centero Disaccharide, tri-tetra etc from 2-10 units.o Oligosaccharide greater than 10o Polysaccharide: larger polymer 10’s to 1000’s, may be linear or branched. MW of> than 1x106 possible.-Know structures of Glucose and Fructose both linear (Fischer) form and Haworth.-Identify the anomeric carbon and know the alpha and beta ring structures.o Anomers: a new chiral center formed upon cyclization. Designated as a or b depending on direction of new alcohol functionality alpha is down and beta is up-Know isomer nomenclature: Epimer, Diastereomer, Constitutional isomer, Anomer , Enantiomer.o Enantiomer: non-superimposable mirror images- either D or L using a fishcher projection By convention, for monosaccharides with 2 or more asymmetric centers (diastereomers) the prefix D- or L- refers to the configuration of the carbon with the highest # (the asymmetric carbon furthest from the carbonyl carbon).o Diastereomer: multiple chiral centers, not mirror imageso Epimer: diastereomers that differ at only one chiral center Epimers are a kind of diastereomer-Linkages, know what they are and how to draw them and resulting polymers i.e. Glycogen alpha 14 linkages (with alpha 16 branches). o When put two monomers together=glycosidic bondD-glucose alpha-1,6 D-Glucoseo Sugar Polymers Can be broken down into three classes:1. Unmodified glucose polymerso i. alpha-linked: α1->4 linkage causes a KINK=Many H-bonds are made between the Glc and waterii. beta-linked: i.e cellulose(most abundant nature polymer in world)= forms long flat stackable polymersi.e chitin= antiparallel and a mix otherwise similar to cellulose** Aliginate can be alpha or beta or both2. Modified glucose polymers3. Mixed sugar polymerso Polysaccharides allow many Glc molecules to be stored in a cell with little effect on osmolarity (osmolarity depends on # of molecules, not their size). – Branching helps present many non-reducing ends (on the many chains in the branched polymer) to enzymes that break down polysaccharides – so we can quickly produce glucose when we need it-Know the difference between proteoglycan and a glycoprotein and their functions?o Glycoproteins: Covalently-linked oligosaccharide and proteins. Main function (and usually mass) comes from the protein. Mainly proteins with a little carb Most secreted proteins are glycosylated. Include structural proteins, enzymes, membrane receptors transport proteins, immunoglobulins… Bacteria don’t do this. Can be O-linked: often found in suface glycoproteins and mucins(to Ser, Thr, or hydroxylysine) (N-acetylglucosamine although Mann, Gal, Xyl also N-Linked: linked to mannose triad – to Asn (N-acetylgalactosamine and rich in sialic acids).o Proteoglycan: mainly carb with some protein Example: cartilageLecture 15 (March 2) Chapter 11: Lipids-Roles for fatty acids and lipidso Lipid is a generic term for any biological molecule that has low water solubility.o Many biomolecules can fall into this category so the exact definition is somewhathazy. Generally regarded as the categories described under Structures in slide 1.o Generally the structures we are describing as lipids have numerous reduced carbons in large chains. This gives them significant upside with regard to oxidation potential.o Lipids can be classified as either hydrophobic or amphipathic(has both polar and nonpolar parts).o At physiological pH the carboxyl group is ionized.o Most fatty acids have an even number of carbons because they are made from the two carbon acetyl CoA precursor.o Most of the biologically relevant fatty acids fall in the number range of C12-C24.o Fatty acids can be