Cheat Sheet - Final Biochem Part I

Capitulo 2 1- Cell membranes are semipermeable, and osmosis is an ongoing process in the body. Differences in osmotic pressure inside and outside a red blood cell can result in crenation (shriveling) or hemolysis (rupture). The diagram shows three solutions: an isotonic solution, a hypertonic solution, and a hypotonic solution. Place the appropriate red blood cell in each solution. 2- Aspargine is a polar acid, shown at pH 7. What is the maximum number of water molecules that, in theory, one aspargine molecule at pH 7 can hydrogen bond with? 3- The concentration of acetylcholine (a neurotransmitter) in a sample can be determined from the pH changes that accompany is hydrolysis. When the sample is incubated with the enzyme acetylcholinesterase; 4- How does a buffer resist change in pH upon addition of a strong acid? 5- What is the pH of a 40.0   mL solution that is 0.15   M in CN  − and 0.29 M in HCN  ? The ka  for HCN is 4.9×10   . −9 6- Arrange the intermolecular forces according to their relative strengths. 7- Classify each molecule as hydrophilic, hydrophobic, or amphipathic (amphiphilic). 8- Freediving is an activity in which a person dives, sometimes to great depth, without the use of scuba gear. The diver must hold his or her breath for the duration of the dive. The record depth, with no equipment such as diving fins, is 101 m; the official record time is over 11 minutes. Historically, freediving has been used by pearl divers and sponge divers. 9- Urea is an organic compound widely used as a fertilizer. Its solubility in water allows it to be made into aqueous fertilizer solutions and applied to crops in a spray. 10- A patient is suspected of having low stomach acid, a condition known as hypochloridia. 11- Classify the compounds according to the pH condition that would improve their solubility in water. 12- Which acid and its conjugate base would be the best buffer at pH=6.0? 13- Acetone can dissolve sodium iodide. 14- Select the hydrophilic species. 15- What is the ratio [A  − ]/[HA] at pH 2.75?   The p   𝐾a of formic acid (methanoic acid, H−COOH) is 3.75. 16- A monoprotic weak acid, HA  , dissociates in water according to the reaction 17- Which of the following compounds is most soluble in water? 18- Identify the predominant intermolecular forces in each of the given substances. 19- The components of poison ivy and poison oak that produce the characteristic itchy rash are catechols substituted with long-chain alkyl groups. 20- You need to prepare an acetate buffer of pH 5.31 from a 0.735 M acetic acid solution and a 2.32 M KOH solution. If you have 630 mL of the acetic acid solution, how many milliliters of the KOH solution do you need to add to make a buffer of pH 5.31? The p𝐾a of acetic acid is 4.76. 21- Which three statements accurately describe the blood buffering system in humans? 22- Write the Henderson-Hasselbalch equation for a propanoic acid solution (CH  3 CH2 CO2 H, pka =4.874) using the symbols HA and A− , and the given p  𝐾  a value for propanoic acid in the expression. 23- During exercise when the body lacks an adequate supply of oxygen to support energy production, the pyruvate that is produced from the breakdown of glucose is converted into lactate. High lactate levels can lead to acidity in the muscle cells as some of the lactate hydrolyzes to lactic acid. 24- Covalent bonds place constraints on the shapes of biological molecules. As the size and complexity of a biomolecule increases, the chemical focus shifts from covalent bonds to noncovalent interactions. Noncovalent interactions dictate the stable, native conformations of large macromolecules and polymers while permitting the flexibility necessary for their biological functions. 25- Identify the characteristics of intermolecular interactions including hydrogen bonding, ion–dipole, and the hydrophobic effect. 26- When 3.42 g of a nonelectrolyte solute is dissolved in water to make 465 mL of solution at 27 °C, the solution exerts an osmotic pressure of 873 torr.