Exam I/Biochemistry I/Fall 2002/ Dr. Stone
1.Acid-Base review.
What is the pH of a .005 M solution of KOH?
What is the pH of a solution made by adding 50 ml of 1.20M HCl to 450 mL of water.
What is the pH of a 0.05 M solution of acetic acid?
2. Draw the titration curve (pH vs amount of NaOH added) for the titration of a 0.1 M solution of acetic acid with 0. M sodium hydroxide. Be sure to show the starting pH (no NaOH added), the equivalence point, and the point that is half way to the equivalence point. Be sure to label both axes correctly.
3. You need to make a buffer for your biochemistry laboratory experiment that involves intestinal mucosa cells. These cells require a pH of 6.7 to survive. Give the complete directions (including substances, volumes and weights) for preparing 400 mL of this 0.15M buffer solution.
4. Phosphoric acid is a weak acid and can be used to prepare buffer solutions. If 500mL of 0.1M phosphoric acid has a starting pH of 7.4, and then an amount of 0.1M NaOH is added to this buffer to change the pH to 8.2, what volume of 0.05M NaOH has been added?
5. Acetylcholine is a potent neurotransmitter. Concentrations in the synapses between nerves is regulated by the enzyme acetocholinesterase. This enzyme degrades acetocholine to choline and acetic acid. The acetic acid then dissociates to acetate ion and hydrogen ion. Calculate the moles of acetylcholine present in 0.05 ml if the addition of acetylcholinesterase decreases the pH from 7.4 to 7.3. (The Ka for acetic acid is 1.74 x 10-5.)
6. Cigarette manufacturers tend to add all sorts of chemicals to make their products more effective nicotine delivery devices. The Ka for nicotine is 8.31 x 10-9. One of these additives is ammonia. (Ammonia is a base.)
a. Circle the species of nicotine that predominates at pH 10. (sorry pictures not available now.)
b. Put a square around the species of nicotine that is the most hydrophobic.
7. (12 points) Draw the structures and give the names and three letter codes for these amino acids.
|
T (at pH 7.0) |
H (at pH 7.0) |
|
W (at pH 7.0) |
N (at pH 70) |
|
G (at pH 7.0) |
R (at pH 7.0) |
8. An unconscious, 67 year old, 70 kg male is brought into the ER. Dr. Dewgi orders blood gases and blood pH to be determined. The results of the tests indicate that the patient has metabolic acidosis.
Normal values
pH = 7.4
CO2 = 1.2 mM
HCO3- = 24 mM
Patient
CO2 = 1.1mM
pH = 7.03
Dr. Dewgi didn’t take his Chemistry II seriously, so now you need to help him save his patient!
Determine the amount of bicarbonate in the patient’s blood.
How much bicarbonate (it is packaged in 50 mL ampules that contain 1 mEq/mL,1mEq = 1 mmole for bicarbonate) should be given to this pt (pt = patient) to restore his bicarbonate levels? (The total blood volume of a 70 kg male is 5.6L.)
Why is bicarbonate so important?
9. It’s a busy night in the ER, Dr. Dewgi didn’t get any time to flirt with Dr. Nosital. The next pt was a 21 year old, 65kg male in a coma who was breathing very slowly with episodes of apnea. The pts buddys ditched him at the door and ran off, but their erratic behavior was noted by the door guard. All signs pointed to a narcotic overdose. Dr. Dewgi ordered CO2 levels and blood pH. The results indicate that the pt has respiratory acidosis.
Pt values: pH = 7.22 CO2 = 1.9 mM
Dr Dewgi was about give the order to inject the pt with bicarbonate when Dr. Nosital popped in to save the day.
What is the pt’s bicarbonate level?
What would be a better treatment for this patient?