Amphipathic Molecule
As it pertains to the biological systems, explain what is meant by “dynamic steady state.” Provide examples Explain what is meant by the term an “amphipathic” molecule. Provide examples Explain what sets the lower limit of the cell size and the upper limit. The antidepressant medication citalopram (trade name Celexa), a selective serotonin reuptake inhibitor, is a racemic mixture of the two isomers, but only (S)-citalopram has the therapeutic effect. A stereo chemically pure preparation of (S)-citalopram (escitalopram oxalate) is sold under the trend name Lexapro. Explain what is meant by “stereospecificity Explain why ionic attractions are weaker in media with high dielectric constants, e. g., water and aqueous buffers. Explain how cellular communication occurs on molecular and cellular levels. Provide examples. In regards to the protein structure, explain what is meant by “quaternary structure.” What are the main forces that stabilize quaternary structures in proteins? Provide examples.
In your understanding, do you think that the following statement is correct: “Water is an effective solvent for living systems because of its inert behavior”? Why or why not? Explain your answer. Explain Endosymbiotic Theory; provide supporting evidence that substantiates this theory. Explain why hydrophobic molecules aggregate together when placed in water and aqueous buffers. What is the thermodynamic driving force for this separation? Amino acid thyroxine is an iodine containing biological derivative of tyrosine and is a major hormone, T4, secreted by the follicular cells of the thyroid gland. The three pKa values for thyroxine are pK1 = 2.2, pK2 = 10.1, and pKR = 6.5 (see structure below). Would it be correct to say that at physiological pH 7.4, [Fully deprotonated thyroxine] > [Fully ionized thyroxine]? Explain your answer. Explain why those biological reactions that have their equilibria shifted towards the products have negative values for ΔGo of reactions. Explain how equilibria relates to Gibbs free energy. Explain why synthesis of a dipeptide from two individual amino acids is energetically unfavorable.
Explain how this unfavorable synthesis occurs in biological systems. The mitochondrial enzyme fumarase is involved in the Krebs Cycle, and catalyzes the reversible hydration of fumarate to (S)-malate. What is the ΔGo′ (in kJ/mol) for the forward reaction catalyzed by mitochondrial fumarase at an average adult body temperature of 37 oC? Equilibrium concentrations of the reactants and products are given below for each of the components. You must show your calculations. Normally, in mammals the body maintains the blood glucose level at a reference range between 3.6 and 5.8 mM (mmol/L). It is tightly regulated as a part of metabolic homeostasis. Explain what would happen if red blood cells were placed into a solution containing 0.5 mM glucose; what would be the term that describes this solution? The pH of blood in normal individuals is 7.4, while alcohol abuse may result in blood pH elevated to as high as 8.0, a condition known as metabolic alkalosis. Calculate the ratio of hydronium ions in blood of a normal individual to that of a person with alcohol abuse.
You must show your calculations. MOPS (3-(N-morpholino) propane sulfonic acid) is a physiologically relevant acid has a pKa of 7.2. What would be pH of the buffer prepared from equal amounts of 15 mM MOPS acid and 6 mM MOPS base? Show your calculations. Would this prepared buffer be a suitable buffer? Explain your answer. Calculate the molar extinction coefficient of tryptophan (in M‒1cm‒1) (MW 204.23 g/mol) if 0.01 g sample is prepared in 100 mL buffer, the above solution produced an absorbance of 2.74 when using a spectrophotometer with a cuvette path length of l = 1 cm. Calculate the net charge on the following nonapeptide at the physiological pH 7.4, and predict the peptide’s mobility in an electric field. Explain your answer. Tyr – Ala – Phe – Lys – Gly – Cys – Ser – His – Asp Explain how the directionality of bonding may affect the strength of the hydrogen bonds A mixture of urease (pI = 5.1; MW 482,000), catalase (pI =5.6; MW 247,500), lactoglobulin (pI = 5.2; MW 37,100) and hemoglobin (pI = 6.9; MW 64,500) were applied in a pH 6.5 buffer to a CM-cellulose (cation exchanger resin) chromatography column and eluted with the same buffer. What is their order of elution? How would you elute bound proteins from this type of resin? Explain your answer. Explain the theory behind gel filtration chromatography.
In a mixture of five proteins listed, draw an elution profile (Absorbance vs. mL eluted, arbitrary) for the purification of the listed proteins on a gel filtration chromatography resin: Cytochrome c (Mr = 13,000), Immunoglobulin G (Mr = 145,000), Ribonuclease A (Mr = 13,700), RNA polymerase (Mr = 450,000), Serum albumin (Mr = 68,500). Label your elution peaks.Draw a sketch of an SDS-PAGE, reflecting the mobility of the above mixture as they elute from the column. Label you protein bands.A peptide was found to have a molecular mass of about 550 and upon hydrolysis produced Ala, Asp, Cys, Lys and Phe in a 1:1:1:1:1 ration. The peptide upon treatment with Sanger’s reagent (FDNB) produced DNP-Cys and upon exposure to carboxypeptidase produced aspartate residue. Chymotrypsin treatment of the above peptide produced a dipeptide that contained sulfur and had a UV absorbance, and a tripeptide. Exposure of the original peptide to trypsin produced a dipeptide and a tripeptide. Deduce the sequence of the peptide analyzed. Explain in detail the rationale behind your answer.
