Questions:

1. The two most important buffer systems in blood are:
  1. Phosphorylated organic metabolites and hemoglobin
  2. Inorganic phosphate and hemoglobin
  3. Phosphorylated organic metabolites and pyruvate
  4. Hemoglobin and bicarbonate
  5. Hemoglobin and albumin
2. The pH of blood changes from normal to 7.25. As a result, the patient will:
  1. Breathe more slowly and the carbonic acid concentration will rise
  2. Breathe more slowly and the serum bicarbonate concentration will rise
  3. Breathe more slowly and the pH will rise
  4. Breathe more quickly and the bicarbonate concentration will rise
  5. Breathe more quickly and the carbonic acid concentration will drop
3. Di Beatty is a patient who has had IDDM for seven years. She missed her scheduled insulin shot and ate a candy bar. She was brought to the clinic after developing ketoacidosis.. Compared to normal, you would expect:
  1. higher PaCO2 and higher serum bicarbonate
  2. lower PaCO2 and higher serum bicarbonate
  3. lower PaCO2 and lower serum bicarbonate
  4. higher PaCO2 and lower serum bicarbonate
  5. no change in PaCO2 and higher bicarbonate
4. An acid anhydride is formed by removing water from
  1. A sulfhydryl group and a carboxylic acid
  2. An alcohol and a carboxylic acid
  3. An amino group and a carboxylic acid
  4. An alcohol group and an inorganic phosphate
  5. A carboxylic acid and an inorganic phosphate
5. The R-groups of the amino acids valine, leucine, and isoleucine are all:
  1. Nonpolar and aromatic
  2. Polar and hydrophobic
  3. Hydrophilic and branched chain
  4. Polar and charged
  5. Nonpolar and branched chain

6. The pKa's for this amino acid are 2, 9, and 10.5. At a pH of 7.4, this amino acid has a net positive charge. The amino acid is:
  1. Cystine
  2. Histidine
  3. Lysine
  4. Asparagine
  5. Valine
7. At pH of 7, a salt bond would most likely form between the R-groups of:
  1. Valine and alanine
  2. Histidine and lysine
  3. Aspartate and arginine
  4. Arginine and lysine
  5. Histidine and glutamate
8. Treatment for cystinurea could include:
  1. Oxidation of cystine to form 2 cysteine molecules
  2. Reduction of cystine to form carboxyl groups which would be more soluble
  3. Reduction of methionine in the diet, since this is a precursor to the synthesis of cysteine
  4. Feeding of reduced glutathione, since this will oxidize cystine
  5. Forming a salt bond between the disulfide bond and the R-group of glycine
9. In this type of structure, most of carbonyl groups of peptide bonds forms a hydrogen bond with the amide nitrogen of another peptide bond four amino acids further down the polypeptide chain.:
  1. Alpha-helix
  2. Beta-sheet
  3. Beta-turn
  4. Quaternary
  5. Primary
10. Concerning prion disease, the amyloid protein in the brain is thought to result from
  1. The repression of the PrPc gene
  2. The accelerated conversion of PrPsc to amino acids
  3. The raising of the activation energy for the conversion of PrPsc to PrPc
  4. The raising of the activation energy for the conversion of PrPc to PrPsc
  5. The lowering of the activation energy for the conversion of PrPc to PrPsc
11. Which of the following terms describes hemoglobin but not myoglobin?
  1. The protein contains hydrogen bonds
  2. The protein contains a hydrophobic pocket that contains heme
  3. Imidazole groups stabilize the ferrous ion
  4. Hydrophobic interactions are partially responsible for the conformation of the molecule
  5. The protein contains alpha and beta chains

12. Concerning Di Abietes, HbA1c
  1. Measures blood glucose levels since birth
  2. Is high when the enzyme hemoglobin glycosylase is active
  3. Is best used to measure compliance over the last three days
  4. Is lower if the person lives in a cold climate
  5. Measures compliance over the last 6 weeks to eight weeks
13. The alpha helix found in myoglobin can best be described as
  1. Primary structure
  2. Secondary structure
  3. Tertiary structure
  4. Quaternary structure
  5. Motif structure
14. Will Sichel has sickel cell anemia. His beta-chains are changed by the substitution of :
  1. a nonpolar valine for a charged glutamate
  2. a nonpolar glutamate for a charged valine
  3. a polar valine for a polar glutamate
  4. a nonpolar valine for a nonpolar glutamate
  5. a charged valine for a noncharged aspartate
15. You have an aqueous solution on your lab bench. The concentration of hydroxide ions is 5 x 10-7. You can determine:
  1. That the proton concentration is 2 x 10-6
  2. That the proton concentration is 2 x 10-8
  3. That the proton concentration is 1 x 10-14
  4. That this is definitely a buffered solution
  5. Nothing, not enough data is presented here
16. Phosphate buffer in blood has a pKa = 6.8. If the pH of blood was 7.1, and the concentration of HPO4 was 0.8 mmol/L , What would be the concentration of H2PO4?
  1. 8 mmol/L
  2. 4 mmol/L
  3. 0.8 mmol/L
  4. 0.4 mmol/L
  5. 0.2 mmol/L

17. Which of the following statements about buffers are TRUE?
  1. Their effectiveness does not depend upon their concentration
  2. Maintenance of blood pH relies solely on the bicarbonate buffering system
  3. They usually consist of a strong acid and its conjugate base
  4. Buffers work best when the pH of the solution is within 1 pH unit of its pKa
  5. Although some problems may arise, the body could survive without buffers
18. You are working with arterial blood. The patient is acidotic with a pH = 7.1. The pKa for carbonic acid is 6.1. The partial pressure of CO2 is 37 mm Hg. The concentration of CO2 is 1.1 mM. What is the concentration of bicarbonate ion?
  1. 44 mM
  2. 22 mM
  3. 11 mM
  4. 1.1mM
  5. 0.11 mM
19. Which of the following statements regarding monosaccharides is FALSE?
  1. D-glucose and D-galactose differ in the orientation of one hydroxyl group; thus, they are epimers
  2. D-glucose and D-galactose are stereoisomers
  3. Most monosaccharides in humans exist in the D-configuration
  4. Monosaccharides in solution usually exist as ringed structures
  5. Gluconate and glucuronate are both formed by the reduction of glucose
20. An amide bond is formed from a
  1. sulfhydryl group and a carboxyl group
  2. carboxyl group and an amino group
  3. phosphate group and an alcohol group
  4. phosphate groupe and a carboxyl group
  5. carboxyl group and another carboxyl group
21. At physiologic pH, which R-groups of the following pairs could successfully form a salt bond?
  1. Phe - Trp
  2. Asn - Val
  3. Glu - Arg
  4. Met - Cys
  5. Ala - Arg
22. Which of the following amino acids has an isoelectric point of about 11
  1. Leucine
  2. Tryptophan
  3. Methionine
  4. Aspartate
  5. Arginine

23. All of the following are treatments for cystinuria EXCEPT:
  1. Increase fluid intake
  2. Increased protein in the diet
  3. Reduce methionine intake in diet
  4. Sonic fracturing of cystine stones
  5. Drugs which convert cystine to more soluble compounds
24. Which R-group of the following is MOST likely to form hydrogen bonds in aqueous solution?
  1. Proline
  2. Alanine
  3. Serine
  4. Isoleucine
  5. Valine
25. One of the following is NOT usually a force that helps to hold the monomer units of a quaternary protein together?
  1. Peptide bonds
  2. Disulfide bonds
  3. Hydrogen bonds
  4. Salt bonds
  5. Hydrophobic interactions
26. Of the following states of hemoglobin (Hb), which is least likely to bind the next molecule of oxygen (02)?
  1. Hb
  2. Hb (02)
  3. Hb (02)2
  4. Hb (02)3
27. Assume that an acid and the salt of an acid are equally soluble at pH 7.7 and that the pKa for the conversion of the salt to the acid is 5.7. As you add either the salt of the acid or the acid to a solution buffered at 7.7, which would precipitate first?
  1. The salt of the acid
  2. The acid
28. Which of the following statements regarding ligand binding is NOT correct?
  1. Some proteins require ligands in order to perform their function
  2. Enzymes with their attached ligands are called holoenzymes
  3. Ligands are synonymous with prosthetic groups
  4. The heme group on hemoglobin is an example of a tightly bound ligand
  5. Some apoproteins will bind to ligands

29. Concerning a patient with diabetic ketoacidosis, which compound in her blood reacts with nitroprusside?
  1. Glucose
  2. Glucose oxidase
  3. Beta-hydroxybutyrate
  4. Acetoacetate
  5. A long chain fatty acid
30. Which of the following is a free radical?
  1. N2
  2. O2-
  3. OH-
  4. alanine
  5. NAD+
31. Regarding any untreated person having diabetes, what level of fasting blood sugar would you expect?
  1. 55 mg/dL
  2. 70 mg/dl
  3. 90 mg/dl
  4. 110 mg/dL
  5. 126 mg/dL
32. If a person breathes into a paper bag, you would expect their blood CO2 to
  1. decrease and their blood pH to increase
  2. decrease and their blood pH to decrease
  3. increase and their blood pH to increase
  4. increase and their blood pH to decrease
  5. remain the same because the kidney determines the blood CO2 concentration
33. A thioester is formed by removing water from
  1. A sulfhydryl group and a carboxylic acid
  2. An alcohol and a carboxylic acid
  3. An amino group and a carboxylic acid
  4. An alcohol group and an inorganic phosphate
  5. A carboxylic acid and an inorganic phosphate

34. Refer to the structures in Figure 1 below. Which column contains the structure for a ketohexose?
  1. Column A
  2. Column B
  3. Column C
  4. Column D
  5. Column E
Figure 1.Five possible curves for an allosteric activator added to an allosteric enzyme.
35. Refer to the structures in Figure 1 above. Which column contains both sorbitol and a ketose?
  1. Column A
  2. Column B
  3. Column C
  4. Column D
  5. Column E

36. Refer to the structures in Figure 2 below. Which column contains the structure for adenine?
  1. Column A
  2. Column B
  3. Column C
  4. Column D
Figure 2.Five possible curves for an allosteric activator added to an allosteric enzyme.

Answers:

As a reference point, previous classes scored a combined mean of 75% for questions 1 through 36. Some answers have a Help link attached.
1. Answer: D, 100%. Chapter 4, Objective 10: "What are the two main buffers in blood?"
2. Answer: E, 65%. Chapter 4, Objective 11: "Be able to draw the equations that show how the bicarbonate buffer system works in blood! What is the respiratory compensation when the blood pH drops to 7.3? What is the respiratory compensation when the blood pH rises to 7.5?"
3. Answer: C, 42%. Chapter 4, Objective 14: "Regarding the Di Beatty Case...Explain why an increase in a metabolic acid would cause the changes seen in PaCO2 and serum bicarbonate. What would happen to the concentration CO2 and serum bicarbonate after the insulin injection?"
4. Answer: E, 68% Ch 5, Objective 3, "What are the substrates for a reaction that forms an ester, a thioester, an amide, a phosphoester, and an acid anhydride? What are the products of a reaction that hydrolyzes an ester, a thioester, an amide, a phosphoester, and an acid anhydride?"
5. Answer: E, 93%. Chapter 6, Objective 5: "Be able to name the structures of all 20 amino acids. Be able to say which contain R-groups that are nonpolar, polar, or charged. Be able to predict which R groups should be soluble in water and which should not"
6. Answer: C, 87%.Chapter 6, Objective 10: "Given the pH, predict whether the amino acids aspartic acid, glutamic acid, histidine, lysine, and arginine would be neutral or would carry a net negative or net positive charge."
7. Answer: C, 64%. Chapter 6, Objective 8: "Given any two amino acids, predict whether their R-groups could form a salt bond at pH = 7.4"
8. Answer: C, 64%. Chapter 6, Objectives 6 and 17: "Be able to recognize cysteine, cystine, a sulfhydryl group, and a disulfide bond. Which are more oxidized and which are more reduced?" and "Concerning Cal Kullis: To the extent covered in this chapter, explain his disease in terms of amino acids."
9. Answer: A, 89%. Chapter 7 Objective 2: "Be able to recognize and discern between the three types of secondary structure discussed in class!"
10. Answer: E, 70%. Chapter 7, Objective 23: "Explain how a prion can cause dementia and death. Include the terms PrPc, PrPsc, template, activation energy, cascade, amyloid protein, and proteolytic degradation"
11. Answer: E, 79%. Chapter 7, Objective 14: "Using the terms ferrous iron, heme, hydrophobic pocket, imidazole group, histidine, alpha-helix, alpha-turns, salt bonds, hydrophobic interactions, hydrogen bonds, oxygen, and subunits, describe the myoglobin and hemoglobin molecule"
12. Answer: E, 73%. Chapter 7, Objective 27: "Concerning Di Abietes, What is HbA1c? How is it made and what does it measure?"
13. Answer: B, 90%. Chapter 7, Objective 1: "Understand the meaning of primary, secondary, tertiary, and quaternary structure and be able to discern the difference." Objective 6: "What is a motif? " Objective 14: "Using the terms ferrous iron, heme, hydrophobic pocket, histidine, alpha-helix, alpha-turns, salt bonds, hydrophobic interactions, hydrogen bonds, oxygen, and subunits, describe the myoglobin and hemoglobin molecule. "

14. Answer: A, 80%. Chapter 7, Objective 24: " Concerning Will Sichel: In biochemical terms, explain the development of pain during a sickle cell crises. Include the specific mutation, oxygen pressure, and protein conformation in your answer.?"
15. Answer: B, 61% Ch. 4, Objective 2; "Define the ion product for water. Given any hydroxide ion concentration, determine the hydrogen ion concentration and vice versa."
16. Answer: D, 86% Ch. 4, Objective 4; "Given a weak acid, be able to draw the equation for its dissociation and label the conjugate base (salt of the acid). Be able to define the Ka for the acid. Be able to write the Henderson-Hasselbalch equation for acid."
17. Answer: D, 98% Ch. 4, Objective 5; "Define the term buffer. Name two factors that determine the effectiveness of the buffer. At what pH are buffers most effective?"
18. Answer: C, 59% Ch. 4, Objectives 4 and 8; "Given a weak acid, be able to draw the equation for its dissociation and label the conjugate base (salt of the acid). Be able to define the Ka for the acid. Be able to write the Henderson-Hasselbalch equation for acid.""Be able to draw the equations that show how the bicarbonate buffer system works in blood. What is the respiratory compensation when the blood pH drops to 7.3? What is the respiratory compensation when the blood pH rises to 7.5?"
19. Answer: E, 68% Ch. 5, Objectives 7, 8 and 9; "Given two compounds, be able to tell whether they are stereoisomers or epimers!""What is the difference between alpha- and beta-D-glucopyranose?""Compare glucuronate, gluconate, and sorbitol with glucose!"
20. Answer: B, 51%. Ch. 5, Objective 3; "What are the substrates for a reaction that forms an ester, a thioester, an amide, a phosphoester, and an acid anhydride? What are the products of a reaction that hydrolyzes an ester, a thioester, an amide, a phosphoester, and an acid anhydride?"
21. Answer:C, 95% . Ch. 6, Objective 8; "Given any two amino acids, predict whether their R-groups could form a salt bond at pH =7.4."
22. Answer: E, 81%; Ch. 6, Objective 13; Given any amino acid except cysteine, serine, threonine and tyrosine, be able to predict the isoelectric point."
23. Answer: B, 89% Ch.6, Objective 17; "Concerning Cal Kullis: To the extent covered in this chapter, explain his disease in terms of amino acids"
24. Answer: C, 84% Ch. 6, Objective 5 "Be able to name the structures of all 20 amino acids. Be able to say which contain R-groups that are nonpolar, polar, or charged. Be able to predict which R groups should be soluble in water and which should not"
25. Answer: A, 95% Ch. 7, Objective 12 "What are the forces that hold the monomer units of a quaternary structure together?"
26. Answer:A, 86% Ch. 7, Objective 18 " Be able to explain why the oxygen saturation curve for hemoglobin is sigmoidal while the curve for myoglobin is a rectangular hyperbola. Include the terms subunits, O2, Fe2+, conformation, salt bridges, T-state, R-state.?"

27. Answer: A, 75% Ch 5, Objective29, "Concerning Lotta Topaigne, Given that the pKa for uric acid is 5.7 and that uric acid is 20 times less soluble than sodium urate, explain which is more likely to precipitate in the toe and which is more likely to precipitate in the kidney tubule"
28. Answer: C, 36% Ch. 7, Objective 16; "What is a ligand?"
29. Answer: D, 77% Ch 5, Objective 25, "Concerning Di Abetes, what two compounds were raised in her blood that caused acidosis? Where were they made? Which one was not measured by the nitroprusside reaction and why wasn't it measured?"
30. Answer: B, 57% Ch. 5, Objective 24, "Be able to recognize the structure and name three of the free radicals generated in human tissues!"
31. Answer: E, 70% Ch 4, Objective 15, " Regarding any person suspected of having diabetes: What levels of fasting plasma glucose or levels of random plasma glucose would you expect to measure?"
32. Answer: D, 68% Ch 4, Objective 17, "Regarding Percy Veere: Using the Henderson-Hasselbalch equation, explain the effect of breathing into a paper bag upon blood pH."
33. Answer: A, 75% Ch 5, Objective 3, "What are the substrates for a reaction that forms an ester, a thioester, an amide, a phosphoester, and an acid anhydride? What are the products of a reaction that hydrolyzes an ester, a thioester, an amide, a phosphoester, and an acid anhydride?"
34. Answer: D, 88%. Chapter 5, Objectives 4 and 5: "Be able to recognize a aldose and ketose.!"" Be able to recognize a triose, tetrose, pentose, hexose, heptose!"
35. Answer: D, 70% Ch. 5, Objectives 4 and 9 ; "Be able to recognize a aldose and ketose.! " " Compare glucuronate, gluconate, and sorbitol with glucose!"
36. Answer: A, 70%. Ch. 5, Objective 21, "Be able to recognize the structure of a purine and a pyrimidine base. Be able to identify the structure of adenine, guanine or thymine."

Selected Answers to Some Questions on Examination 1

Help for Examination 1, Question 4

Removing water from between two acids forms an acid anhydride.  Only Answer E has two acids.  Water is removed from the other choices but they do not contain two acids.  Answer A forms a thioester (the SH is considered equivalent to an alcohol).  Answer B and D also form esters (one acid + one alcohol).  Answer C forms a amide bond ( amino group + acid group)

Help for Examination 1, Question 7:

At pH=7 the R group of aspartate is negative and the R-group of arginine is positive.
At pH=7 the R-group of histidine is neutral and the R-group of glutamate is negative.
Both of the above are determined from using the pKa of the R-group and knowing the charge on the R-group.

Help for Examination 1, Question 15:

Kw = 1 X 10-14 = [OH-][H+] and [OH-] = 5 X 10-7

1 X 10-14 = (5 X 10-7)[H+]

Or, [H+] = (1 X 10-14) /(5 X 10-7) = (10 X 10-15) /(5 X 10-7)

Since 10 / 5 = 2 and (-15)- (-7) = -8

[H+] = 2 X 10-8

To check, [5X10-7] [2 X 10-8] = 10 X 10-15 = 1 X 10-14

Help for Examination 1, Question 16:

Since pH = 7.1 and pKa = 6.8

Use the Henderson Hasselbalch equation: 7.1= 6.8 + Log [(HPO42-)/(H2PO4-)]

So 0.3 = log [(HPO42-)/(H2PO4-)]

Since the log 2 = 0.3, then [(HPO42-)/ (H2PO4-)] = 2

And since HPO42- = 0.8, then [0.8/(H2PO4-)] = 2

and HPO42- = 0.4 mmol/L

Help for Examination 1, Question 18

Use the Henderson Hasselbalch equation: 7.1 = 6.1 + Log [(HCO3-)/(H2CO3)]

Saying 37 mm Hg is exactly the same as saying 1.1 mmol/L Remember that you multiply mmHg by 0.03 to get mM.

So 7.1 = 6.1 + Log [(HCO3-)/1.1)]

Or, 1= Log [(HCO3-)/1.1)]

If the Log [(HCO3-)/1.1)] = 1 then (HCO3-)/1.1) = 10

So, HCO3- = 11 mmol/L

Help for Examination 1, Question 27

If the pKa is 5.7 and the pH is 7.7, then according to the Henderson-Hasselbalch Equation, the Log [salt/acid] =2 so, salt/acid =100.  That is, there are 100 molecules of salt for every molecule of acid.  If they are equally soluble, the salt will precipitate long before the acid at pH=7.7.