Biochemistry Central Texas College BIOL 2402 Chelsea Loafman, MS Solutions Solutions are a See figure 2-14 in combination of: text. ◦ Solute: substances dissolved in a liquid ◦ Solvent: the liquid in which the solute dissolves Water is the universal solvent Solubility: how easily it dissolves ◦ Hydrophilic- “water loving” ◦ Hydrophobic- “water fearing” Solution Concentration Solute per solution The amount of solute is expressed in mass (g or mg) or number of molecules (mol) ◦ Mole: 6.02x1023 particles Molarity ◦ Number of moles of a solute in a liter of solution (mol/L or M) Equivalents are used to express the concentration of ions ◦ One equivalent (eq) is the molarity of an ion times the number of charges the ion has Molecular Mass In order to determine the mass of a single molecule: ◦ Find the atomic mass for each element present ◦ Multiply each by how many atoms of the element there are in the whole molecule ◦ Add the totals for each element together to give the mass of the whole molecule The mass of 1 mole of a substance is affected by the molecular mass of that substance Molecular Mass-Glucose (# of atoms) x (atomic mass of the element) = Molecular mass of molecule Element # of atoms Atomic mass of element Molecular mass Carbon (C) 6 12.0 amu 72.0 amu Hydrogen (H) 12 1.0 amu 12.0 amu Oxygen (O) 6 16.0 amu 96.0 amu Sum Total 180.0 amu Creating Solutions Percent solution allows for a solution to be prepared based on weight/volume rather than particle number (mol) X parts solute per 100 parts solution ◦ 5% glucose solution: 5 grams glucose dissolved in water to make a final volume of 100mL ◦ 0.1% HCl solution: 0.1mL acid dissolved in water to make a final volume of 100mL pH-The Power of Hydrogen pH is a scale used to show the concentration of H+ ions or the acidity of a substance The pH scale runs from 0-14 with each whole number change representing a 10x change in H+ ion concentration The concentration of H+ is inversely related to the concentration of OH- pH Scale Acidic ◦ 0-6.999 See figure 2-15 in ◦ The lower the number the text. more acidic the substance and the higher the H+ concentration Neutral-pure water ◦ 7 ◦ Equal concentration of H+ and OH- (H2O) Basic/Alkaline ◦ 7.0001-14 ◦ The higher the number the more basic/alkaline the substance and the lower the OH- concentration pH Homeostasis Normal body pH is 7.40 and is regulated in a narrow range Alkalosis: pH of 7.5-7.8 ▫ Feelings of being agitated or dizzy ▫ Causes include hyperventilation, mild vomiting Acidosis: pH of 7.0-7.3 ▫ Feelings of being disoriented or fatigued ▫ Causes include impaired breathing, severe vomiting In order to maintain homeostasis we must combat changes in the body’s pH ◦ Buffers combat increasing acidity by having a strong affinity for H+ and therefore taking them “out of play” and stabilizing pH ◦ Bicarbonate anion is a key buffer in the body ◦ Examples: CO2 + H2O H2CO3 HCO3- + H+ (H+ + Cl-) + (HCO3- + Na+) (H2CO3) + (Cl- + Na+) Hydrochloric Sodium Carbonic Sodium Chloride acid Bicarbonate Acid (table salt) Proteins Considered the body’s “work horses” Can be insoluble that provide structural support or soluble that provide one of the following functions: ◦ Enzymes ◦ Membrane transporters ◦ Signal molecules ◦ Receptors ◦ Binding proteins ◦ Regulatory proteins ◦ Immunoglobulin *all contain a binding site Proteins Ligand: a molecule that binds to another See figure 2-16 in ◦ Substrate: ligands that bind to enzymes or membrane text. transporters The ligand must be compatible with the binding site of the protein ◦ Binding occurs through hydrogen bonding, ionic bonding, or van der Waals forces The binding site changes shape slightly to fit snugly with the ligand Proteins are specific about what ligands they will bind to Protein Affinity Proteins have certain attractions to specific ligands called an affinity that will increase the potential for binding Binding of a protein and ligand can be reversible as they go through a dissociation process ◦ P+L PL P+L ◦ Equilibrium is reached when binding rate matches dissociation rate Some ligands become competitors as they fight for the ability to bind with a protein Agonists mimic another ligands action by binding to the receptor site on a protein ◦ Ex: nicotine mimics acetylcholine Protein Binding Affinity can change in See figure 2-17 & different situations to alter the binding ability 2-18 in text. of the protein Isoforms mimic other proteins functionally but carry and affinity for different ligands ◦ Ex-fetal and adult hemoglobin Some proteins need to be activated before they can bind to ligands ◦ Cofactors Modulation of Protein Binding Modulators affect protein binding or activity See figure 2-19 & Chemical modulators 2-20 in text. ◦ Antagonists/inhibitors Competitive inhibitors fight with normal ligands for the binding site (reversible binding) Irreversible inhibitors prevent normal ligand binding permanently ◦ Agonist or antagonist Allosteric modulators bind to a regulatory site that changes the binding site (reversible) Covalent modulators bind covalently to proteins to alter one of the properties of the protein Physical modulators include pH and temperature ◦ Proteins become denatured an lose their confirmation Physical Modulation See figure 2-21 in text. Protein Binding Overview See table 2-3 in text. Protein Numbers Up-regulation: programmed production of proteins to change a cell response Down-regulation: programmed removal of proteins to change a cell response A saturation point can be reached where the response peaks since all of the proteins are saturated with ligands despite a rising number of ligands Up vs Down Regulation See figure 2-22 in text. Saturation See figure 2-23 in text. Example Which has a higher affinity for oxygen? See figure 2-24 in text.
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