* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download introacidbase
Survey
Document related concepts
Genetic code wikipedia , lookup
Citric acid cycle wikipedia , lookup
Photosynthetic reaction centre wikipedia , lookup
Metalloprotein wikipedia , lookup
Basal metabolic rate wikipedia , lookup
Proteolysis wikipedia , lookup
Amino acid synthesis wikipedia , lookup
Fatty acid metabolism wikipedia , lookup
Specialized pro-resolving mediators wikipedia , lookup
Fatty acid synthesis wikipedia , lookup
Butyric acid wikipedia , lookup
Biosynthesis wikipedia , lookup
Transcript
Biochemistry Study of chemistry in biological organisms Understand how the chemical structure of a molecule is determining its function Focus on important biochemical macromolecules – – – – amino acids ----->proteins fatty acids----->lipids nucleotides---> nucleic acids monosaccharides---> carbohydrates Focus on important processes – – – – Protein Function Compartmentalization/regulation MetabolismDNA synthesis/replication Protein Function – What is a protein’s structure and what role does it play in the body? – What are some important proteins in the body? – What are some key principles behind protein’s functions? Enzymes • What are enzymes? • What is the role of enzymes in an organism? • How do they work? Lipids • What are lipids and their structures • What are roles of lipids Membranes and Transport • What is the structure of a membrane? • What is compartmentalization and why is it important? • How can molecules and information get across a membrane? Carbohydrates • What the structures of carbohydrates and what is their role? Metabolism • Glycolysis, Krebs cycle, Oxidative Phosphorylation, beta oxidation • How does a cell convert glucose to energy? • How does a cell convert fat to energy? • Roles of ATP, NAD and FAD • vitamins Nucleic Acids • • • • What are their structures? What their functions? How do they replicate? What is the relationship between nucleic acids and proteins? Connecting structure and function requires chemistry • Chemistry knowledge needed: – – – – Intermolecular forces Properties of water Equilibrium Acid/Base Theory • Definitions • Buffers • Relation of structure to pH Connecting structure and function requires chemistry – – – – Oxidation-Reductions Thermodynamics: study of energy flow Organic functional groups Important organic reactions Intermolecular forces • Hydrogen bonds • Dipole/dipole interactions • Nonpolar forces Dipole/Dipole interactions • Polarity in molecules – Polar bonds – Asymmetry • Positive side of one polar molecule sticks to negative side of another Dipole-Dipole interactions Hydrogen Bonding • Special case of dipole dipole interaction – Hydrogen covalently attached to O, N, F, or Cl sticks to an unshared pair of electrons on another molecule • H-bond donors – Have the hydrogen • H-bond acceptors – Have the unshared pair • Strongest of intermolecular forces Hydrogen bonding Hydrogen bonding • Affect the properties of water • Water has a higher boiling point than expected • Water will dissolve only substances that can interact with its partially negative and partially positive ends Nonpolar forces • Nonpolar molecules stick together weakly • Use London dispersion forces • Examples are carbon based molecules like hydrocarbons • Velcro effect – Many weak interactions can work together to be strong Dissolving process • Solute—solute + solvent—solvent - 2 solute---solvent • Have to break solute—solute interactions as well as solvent—solvent interactions • Replace with solute-solvent interactions Like dissolves like • Hydrophobic = nonpolar • Hydrophilic = polar • Overall, like dissolves like means that polar molecules dissolve in polar solvents and nonpolar solutes dissolve in nonpolar solvents Like dissolves like • Salt dissolving in water Amphipathicity • Some molecules have both a hydrophilic and hydrophobic part • soap is an example Amphipathicity Equilibrium Two opposing processes occurring at the same rate: walking up the down escalator treadmill Equilibrium For chemical equilibrium, It is when two opposing reactions occur at the same rate. mA + nB <= pC + q D – Two reactions: • Forward: mA + nB - pC + qD • Reverse: pC + qD - mA + nB – Equilibrium when rates are equal Reaction Rates Rate of reaction depends on concentration of reactants For the reaction: mA + nB => pC + qD Forward rate (Rf) = kf[A]m[B]n Reverse rate (Rr) = kr[C]p[D]q (rate constants kf and kr as well as superscripts have to be determined experimentally) Equilibrium • When rates are equal: – Rf = Rr so (from previous slide) • kf[A]m[B]n = kr[C]p[D]q – Putting constants together: (Law of Mass Action) • kf = [C]p[D]q = Keq kr [A]m[B]n • Keq is the equilibrium constant • Solids and liquids don’t appear…they have constant concentration Equilibrium in quantitative terms • The equilibrium state is quantified in terms of a constant called the Equilibrium Constant Keq. It is the ratio of products/reactants • It is determined by Law of Mass Action Possible Situations at Equilibrium • 1. There are equal amounts of products and reactants. K=1 or close to it • 2. There are more products than reactants due to strong forward reaction – equilibrium lies right) – K >>1 • 3. There are more reactants than products due to strong reverse reaction – equlibrium lies left Keq Constant Expression • Given the following reactions, write out the equilibrium expression for the reaction • CaCO3(s) + 2HCl(aq) ---> CaCl2(aq) + H2O(l) + CO2(g) • 2SO2(g) + O2(g) --->2SO3(g) Answers [CaCl2][CO2] [HCl]2 [SO3]2 SO2]2 [O2] Le Chatelier’s Principle • When a system at equilibrium is stressed out of equilibrium, it shifts away from the stress to reestablish equilibrium. – Shifts away from what is added – Shifts towards what is removed Le Chatelier’s Examples • N2 + 3 H2 => 2 NH3 – If we add nitrogen or hydrogen, it shifts to the right, making more ammonia – Removal of ammonia accomplishes the same thing – Shifts to the left if add ammonia Le Chatelier’ and Regulation of Metabolism • What the diet industry doesn’t want you to know! – Food - ABCDenergy • A fat – What happens if energy is used up? – What happens if eat a big meal and don’t use energy Acid/Base Theory • Definitions – Acid is a proton (H+) donor • Produces H3O+ in water • HCl + H2O - H3O+ + Cl- – Base is a proton (H+) acceptor • Produces OH- in water • NH3 + H2O > NH4+ + OH- Strong acids v weak acids – Strong 100 percent ionized • No Equilibrium or equilibrium lies to the right • K eq >>> 1 and is too large to measure – Weak acids not completely ionized • Equilibrium reactions • Have Keq – For acids, Keq called a Ka Acetic Acid as Example of a Weak Acid • HC2H3O2(aq) <---> H+(aq) + C2H3O2- (aq) • K = [H+] [C2H3O2-] [HC2H3O2] • value is 1.8 x 10-5 • 1.8 x 10-5 <<< 1 Weak acids, Ka and pKa – pKa = - log Ka – For weak acids, weaker will be less dissociated • Make less H3O+ • Eq lies further to left • Lower Ka – Since pKa and Ka inversely related: the lower the Ka, the higher the pKa, the weaker the acid pH • pH= -log [H+] • increasing the amount of H+ (in an acidic solution), decreases the pH • increasing the amount of OH-decreases the amount of H+ (in a basic solution), therefore, the pH increases • pH< 7 acidic • pH>7 basic Conjugate Base Pairs • Whatever is produced when the acid (HA) donates a proton (H+) is called its conjugate base (A-). • Whatever is produced when the base (B) accepts a proton is called a conjugate acid (HB+). Conjugate Base Pairs • HA(aq)+ H2O(l) H3O+(aq)+ A–(aq) • Acid conjugate base Base conjugate acid • differ by one H+ for acids/bases • Example: HC2H3O2 and C2H3O2• acid conj. base Buffers • A buffer is a solution that resists a change in pH upon addition of small amounts of acid or base. • It is a mixture of a weak acid/weak base conjugate pair – Ex: HA/ A- Buffer with added acid • Weak base component of the buffer neutralizes added acid • A- + H+ -- HA Buffers with added base • Weak acid component of the buffer neutralizes added base • Equation: OH- + HA --> H2O + A- Relationship of pH to structure • We can think of a weak acid, HA, as existing in two forms. – Protonated = HA – Deprotonated = A- • Protonated is the acid • Deprotonated is the conjugate base – Titrated form Henderson-Hasselbach Equation • pH = pKa + log ([A-] / [HA]) • Can be used quantitatively to make buffers • Ka is the equilibrium constant for the acid – HA(aq) + H2O(l) < H3O+(aq) + A-(aq) – Ka = [H3O+][A-] [HA] – Higher Ka = more acidic acid Henderson Hasselbach continued • pH = pKa + log ([A-] / [HA]) • pKa = -logKa Since negative, lower pKa = more acidic Henderson Hasselbach and structure In a titration if we add base to the acid: HA + OH- - H2O + AFor every mole of HA titrated, we form a mole of ASo, if we add enough OH- to use up half the HA (it is half-titrated) we end up with equimolar HA and ALooking at the equation: pH = pKa + log ([A-] / [HA]) If [A-] = [HA] then [A-] / [HA] = 1 and log ([A-] / [HA]) = log (1) – 0 So pH = pKa So what? We can now relate the pH of the solution to the structure of weak acid using Henderson-Hasselbach pH = pKa + log ([A-] / [HA]) If pH = pKa, we have equal amounts of protonated and deprotonated forms If, pH < pKa, means log term is negative so [HA]>[A-] and protonated form dominates If pH > pKa, means log term is postive so [HA] < [Aand deprotonated form dominates.