2Amino Acid Structure Know the parts of an amino acid 1. Amino group 2. Carboxylic Acid (Carboxylate)3. R-Group
3R-GroupsAmino acids are classified by their R-groups and the groups interaction with water1.Hydrophobic-The majority of R-groups2. Polar Uncharged3. Polar Charged
4Hydrophobic R-Groups R-groups composed of only Hydrogen and Carbons One exception- Methionine contains sulfur, bound only to CarbonPhenylalanineMethionine
5Polar uncharged and charged Look for Oxygens and NitrogensCharged groups will be charged or have a primary amine or carboxylic acid part.Primary amines are written NH2 and Carboxylic acids COOH
6Acid Base Properties Amino acids can be proton donors The pH at which the Carboxylate group gives up its proton is the pK1 and the Amino group is pK2pK1 is the point where 50% of the carboxylate groups are unprotonated, and pK2 is where 50% of the amino groups are unprotonatedAmino acids are good buffers at these pointsAdd them together and divide by 2 to get the isoelectric point (pI)This is the point where all amino acids in a solution have zero net chargeAmino acids are bad buffers at this point
7Amino acids can form polypeptides Peptide Linkages: C-N bondDifferent order equals different peptidesEx: Gly-Ala-Pro isn’t the same as Pro-Ala-GlyNumber of possible combinations using each AA once: (Number of Amino Acid)!Ex: tetrapeptide is 4! (4x3x2x1=24)Number of possible combinations using each AA as many times as we want:(number of AA)number in polypeptideEx: 4 amino acids in a tetrapeptide =44
8Amide planes An amide plane forms around the peptide linkage C,N,O,H are involved in the formationThe double bonded O electrons resonate to the C-N bond, giving the peptide linkage a partial double bonded characteristic.
9Protein Substructures PrimaryOrder of the amino acidsEx: ala-gly-asp-leu-lys-pheMain type of interaction: covalent between amino acids, called peptide bondSecondaryAlpha helixMain type of interaction: hydrogen bonds between amide planes
10Protein substructure Tertiary Quaternary Main type of interactions: between R-groupsH-bonds, Electrostatic, Hydrophobic, Covalent (disulfide bonds)Specifically, covalent bond called disulfideBetween 2 cysteines’ sulfhydryl R-groupsQuaternaryLarge molecular weights
11Collagen Predominate AA: proline and glycine Gly- small R-group for rope-like structurePro- Oxidizable R-groupRequires Vitamin C; deficiency=scurvySteps in formationImmature collagen is hydroxylated (-OH groups added) becoming procollagenNeed Vitamin C as reducing agent in this step. If deficient, the person has scurvyProcollagen is glycolyslated (carbohydrate moeities added) making tropocollagenMature collagen formed by crosslinks between hydroxylated prolines
13Gas exchange driven by pH HHb (protonated Hemoglobin) enters lungsLungs are more basic, so HHb more likely to give up protonOxygen (O2) binds to hemoglobin and it gives up the H+HHb+ O2+HCO HbO2+H2O+CO2The bicarbonate is the form that carbon dioxide goes to the lungs as. It travels in the blood plasma.All of the reactions occur inside the red blood cell
14Gas ExchangeOxygenated hemoglobin travels to the tissues where it encounters an acidic enviroment.The acidity is the result of increase carbon dioxide, which is a metabolic byproductIn an acidic environment, hemoglobin tends to give up oxygen and bind the protons that are in the tissuesExtra protons are there as the result of the acid CO2Bicarbonate is moved out of the RBC, exchanged with Chloride (Cl-).
15Gas Exchange Know that pH and Gas Pressures drive respiration Know which direction the equation is goingH2O + HbO2- + CO HHb + O2 + HCO3-Which one occurs in the lungs?Which one occurs in the peripheral tissues?