Chemistry of Life

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2

 

Chemistry of Life: pH and Buffers Student Name Date

Data

 

Activity 1

 

Calculate the volume of 1 M NaOH needed to prepare 10.0 mL of a 0.10 M solution.

 

Calculate the volume of 1 M HCl needed to prepare 10.0 mL of a 0.10 M solution.

 

Data Table 1

 

  Initial pH pH after 1 drop 0.1M HCl pH after 10 drops 0.1M HCl pH after 1 drop 0.1M NaOH pH after 10 drops 0.1M NaOH
Water          
pH 4 buffer          
pH 6 buffer          
pH 8 buffer          

 

 

 

In Activity 1, what happened to the pH of the water sample as 0.1 M HCl was added? How did this compare to what happened with addition of one drop of 0.1 M HCl to each buffer solution?

 

In Activity 1, why did the pH of the buffer solutions change after the addition of 10 drops of 0.1 M NaOH? Activity 2

 

Activity 2

Data Table 2

 

  Initial pH pH after 1 drop 0.1M NaOH pH after 2 drops 0.1M NaOH pH after 4 drops 0.1M NaOH pH after 8 drops 0.1M NaOH
100%          
50%          
25%          
12.5%          

 

 

In Activity 2, which concentration was the effective buffer? Explain what happened chemically as the buffer became more dilute.

 

Explain how the buffer could be diluted (in Activity 2), yet maintain the same pH. Hint: Reference the Henderson-Hasselbalch equation.

 

Photos

 

Photo 1

 

Insert photo of results of Activity 1.

 

The following should be visible in this photo:

· Row and column labels

 

 

Photo 2

 

Insert photo of results of Activity 2.

 

The following should be visible in this photo:

· Row and column labels

 

K:CPMIDistance Learning TeamDL team ImagesDistance Learning Logo.jpg

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Using Genetics To Treat Disease

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* This case study presents a fictitious scenario, but one that is based upon clinical observations.

† Background information on Acute Lymphocytic (Lymphoblastic) Leukemia modified from Satake, N., Acute Lymphoblastic Leukemia, http://www.emedicine.com/ped/topic2587.htm. Last accessed: 07/08/09.

“Pharmacogenetics” by Jeanne Ting Chowning Page 1

by

Jeanne Ting Chowning Department of Education, Northwest Association for Biomedical Research

Part I – Acute Lymphocytic (Lymphoblastic) Leukemia It’s called the children’s ward. For two teenagers who have been recently diagnosed with leukemia, it seems insulting to have their lives hijacked by doctors and nurses with stuffed animals clipped to their stethoscopes.

Laura is a forward on her school soccer team and leads the league in scoring. For the last four months, she has been really tired, but nothing seemed really wrong until her legs became covered with bruises. Just pressing her fingers on her skin was practically enough to make a bruise. It didn’t seem real when her doctor, Jane Ryder, diagnosed her with Acute Lymphocytic (or Lymphoblastic) Leukemia (ALL), or when she told her that ALL is the most common malignant (spreading) cancer found in children. She’s 14 years old; she’s not a child!

Beth is 13 and looks remarkably like Laura. Both have straight dark hair, large brown eyes, and tall slender builds. Beth has never been that athletic; she prefers reading and theater. She’s hoping to be part of the drama team next year when she goes to high school, even though she’ll only be a freshman. But she’s been missing a lot of school because of one virus after another, lots of fevers and night sweats, then that rash in the fall. Now she’s in a hospital, and it seems like the only people she sees are her parents, Dr. Ryder, and the nurses.

Laura and Beth both have ALL, which arises from the uncontrolled growth of immature lymphocytes (a type of white blood cell, or leukocyte). These cells, which are “stuck” in an early stage of development, become so numerous that they crowd out normal blood cells. Each year about 30 cases occur per million people, and most of those cases are in children aged 2–5 years. The cause of ALL remains largely unknown, although a small number of cases are associated with inherited genetic syndromes.† Both girls are suffering from anemia (low blood cell levels), fevers, bleeding, and are pale and thin. Dr. Ryder has decided to treat them as in- patients, keeping them in the hospital while treating them with a “thiopurine” drug called 6-mercaptopurine (6-MP) known to be highly effective in treating leukemia. Thiopurines are very similar to the regular purine nitrogen bases such as adenine and guanine that make up DNA and RNA. The only difference is that thiopurines have an extra sulfur group attached to them. They are similar enough to a regular purine base that our cells convert them to nucleotides (with the addition of a deoxyribose sugar and phosphate). These modified thioguanine nucleotides (TGN) are then incorporated into DNA.

The TGN nucleotides interfere with DNA replication and stop rapidly growing cells like cancer cells from further growth. Unfortunately, they also block the growth of other fast growing cells needed for good health, like the cells in the bone marrow that develop into erythrocytes (red blood cells) and leukocytes. As with

Pharmacogenetics: Using Genetics to Treat Disease*

 

 

“Pharmacogenetics” by Jeanne Ting Chowning Page 2

many drugs given as chemotherapy, it is important to give a high enough dosage to prevent cancer cells from replicating, while avoiding damage to the normal tissues. Too high a drug dose can be very toxic. Dr. Ryder knows that drugs are processed in various ways in the body. They must be absorbed by the blood, distributed throughout the body’s tissues, converted or transformed into forms that are easier to eliminate, and then removed from the body. Dr. Ryder gives both girls the same dosage of the drug before leaving the hospital for the night.

While making her rounds over the next few days, Dr. Ryder sees Laura’s vital signs plummet. Her anemia has worsened; her erythrocyte count is so low that her heart function could be compromised. Her fevers are spiking, and her breathing is becoming shallow and labored. She is not eating and is being hydrated intravenously. Her condition is life-threatening. In contrast, Beth’s anemia has decreased, she is free of fever, and is actually showing signs of an appetite and boredom, good indicators of improved health. Dr. Ryder had not anticipated that the drug could act so differently in two individuals. Even as she looks at Beth’s chart, she can picture Laura’s body struggling to hold its own just two private rooms away. Dr. Ryder knows she must find out why her patients are responding so differently. But where should she start, and will she find an answer in time to help Laura?

Questions 1a. Suggest a reason why the drug might affect the two girls differently.

1b. What tests might Dr. Ryder order to determine why the two girls are reacting as they are to the drug? Provide two or three appropriate examples of tests.

 

 

“Pharmacogenetics” by Jeanne Ting Chowning Page 3

Part II – Enzyme Activity Dr. Ryder learns that the difference in patient reaction to the drug probably has something to do with how the drug is naturally metabolized in the body to be removed as waste. After searching the scientific literature, she learns that the drug 6-MP can either be converted to the active form, TGN nucleotides, or can be inactivated with the help of the TPMT enzyme (thiopurine methyltransferase). Within each patient who takes the drug, both processes are occurring and they compete with each other.

Figure 1. Flow Chart Flow chart showing activiation and inactivation paths of the drug 6-MP.

 

 

“Pharmacogenetics” by Jeanne Ting Chowning Page 4

Since the therapy aims to harm rapidly replicating cells without overly impacting normal ones, it is important that excess drug is inactivated. Dr. Ryder decides to see how levels of the TPMT enzyme activity might vary between people.

She reviews the research papers that have been published about the TPMT enzyme and finds an interesting graph. From a study of 298 randomly selected Caucasian individuals, researchers found the following levels of TPMT enzyme activity:

Figure 2. Simplified Results. Simplified bar graph showing results from a study of 298 randomly selected Caucasian patients.

Questions 2a. If Dr. Ryder had 10 Caucasian patients in the next month, how many would you predict to have each

of the TPMT enzyme activity levels, based on the graph above?

Low:

Medium:

High:

Would you expect the actual/observed number of patients to be different? Why might there be differences?

2b. Each individual inherits two copies of the gene for the enzyme, one from each parent. Dr. Ryder suspects that variation in enzyme activity level is controlled by two different versions (alleles) of that gene. Does this graph (and the number of phenotypes) suggest that enzyme activity levels are based on a dominant/recessive or a codominant pattern of inheritance? Explain your answer.

Source: Simplified graph patterned after the top panel of Figure 2 in: Weinshilboum, R.M., and S. Sladek (1980) Mercaptopurine pharmacogenetics: Monogenic inheritance of erythrocyte thiopurine methyltransferase activity. American Journal of Human Genetics 32:651–662.

 

 

“Pharmacogenetics” by Jeanne Ting Chowning Page 5

2c. Which bar (low, medium, or high) represents individuals who might be homozygous for a “low enzyme activity’” version of the gene? Which bar represents individuals who might be homozygous for a “high enzyme activity” version of the gene? Which bar represents heterozygotes?

2d. Answer the question: “How does enzyme activity level vary among the patients examined?” In your answer, be sure to include supporting data from the graph above. Explain how these data support your conclusion.

2e. Challenge question: The actual graph (below) showed much more detail. Why do you think that there is more variation between patients than shown in the simplified graph?

Figure 3. Histogram RBC TPMT frequency distribution histogram for 298 randomly selected Caucasian subjects.

Source: Histogram drawn after top panel of Figure 2 in: Weinshilboum, R.M., and S. Sladek (1980) Mercaptopurine pharmacogenetics: Monogenic inheritance of erythrocyte thiopurine methyltransferase activity. American Journal of Human Genetics 32:651–662.

 

 

“Pharmacogenetics” by Jeanne Ting Chowning Page 6

Part III – TPMT Enzyme Activity Levels Dr. Ryder tested Laura, who was very sick, and found that her TPMT enzyme activity level was extremely low.

Question 3a. Why would individuals with the lowest level of enzyme get the sickest when they take the drug?

Suggest one possible reason.

Investigating further, Dr. Ryder decides to look at drug levels in many patients who are all receiving the same standard doses of the thiopurine drug and compare them to enzyme levels. When she compares the level of thioguanine nucleotides (TGN) created by the thiopurine drug to the body’s level of TPMT enzyme in patients, this is what she finds:

Figure 4. Scatter Plot of TGN vs. Enzyme Activity Thioguanine nucleotide concentrations and TPMT enzyme activity levels in 95 Children with Acute Lymphoblastic Leukemia (ALL) who were being treated with standard doses of thiopurine drugs.

Source: Modified from Lennard L., J.S. Lilleyman, J. Van Loon, and R.M. Weinshilboum (1990) Genetic variation in response to 6-mercaptopurine for childhood acute lymphoblastic leukaemia. Lancet 336:225–229.

Question 3b. Describe the relationship between TPMT enzyme activity levels and TGN levels. Be sure to include

supporting data from the graph.

 

 

“Pharmacogenetics” by Jeanne Ting Chowning Page 7

Part IV – Putting It All Together From her research, Dr. Ryder hypothesized that patients such as Laura (who became very sick upon receiving the drug) have very high / low TPMT enzyme activity and therefore very high / low levels of TGN nucleotides at normal doses. They easily became sick from the effects of the drug, and could even die. These patients are homozygous / heterozygous for the version of the gene encoding high / low enzyme activity. A better drug dose for these patients is 1/10th the level of other patients.

Patients such as Beth with high / low TPMT enzyme activity had high / low levels of TGN nucleotides. These patients would do well with the drug, and in some cases might even need a larger-than-normal dosage for the treatment to be most effective. These patients were either homozygous for the version of the gene encoding high / low enzyme activity, or were heterozygous.

Based on the graph in Part II, about 10% of the Caucasian population is homozygous / heterozygous.

Question 4. In the paragraphs above, circle the correct answer (high or low, heterozygous or homozygous).

 

 

“Pharmacogenetics” by Jeanne Ting Chowning Page 8

Part V – SNPs and TPMT DNA techniques reveal TPMT gene is located on chromosome 6, is about 34 kilobases in length (34,000 DNA bases), and has 8 exons. An exon is a region of a gene that is present in the final functional transcript (mRNA) from that gene. The diagram below shows a representation of the TPMT gene, showing the exons as boxes. The first “wild type” is the most common version. In our case, the second version of the TPMT gene is associated with low enzyme activity (TPMT*3A) and has two single nucleotide polymorphisms (SNPs), or changes in single DNA nucleotide bases (from “G” to “A” in one case and from “A” to “G” in another) that result in different amino acids being inserted in the enzyme. This, in turn, affects the enzyme’s function. Over 20 different gene variants have been found, three of which are shown below.

Figure 5. Selected Human TPMT Alleles. The wild-type human TPMT allele (TPMT*1) and variant alleles TPMT*3A, TPMT*3B, and TPMT*3C. Rectangles represent exons, with black coding areas and white untranslated regions.

Source: Weinshilboum, R. (2001) Thiopurine pharmacogenetics: Clinical and molecular studies of Thiopurine Methyltransferase, American Society for Pharmacology and Experimental Therapeutics 29:601–605. Available online at http://dmd.aspetjournals.org/. This case is based on this article.

Questions 5a. Dr. Ryder now has the ability to conduct a SNP genetic test on her patients to determine what level

of drug they should get. A new patient on the ward, Kevin, is homozygous for TPMT 3A*. The graph shown in Part III is reproduced on the next page. Circle the area of the graph that might likely corresponds to Kevin’s TGN and enzyme activity levels. Explain why you circled that region.

 

 

“Pharmacogenetics” by Jeanne Ting Chowning Page 9

Case copyright held by the National Center for Case Study Teaching in Science, University at Buffalo, State University of New York. Originally published February 4, 2010. Please see our usage guidelines, which outline our policy concerning permissible reproduction of this work. Title block illustration, licensed, ©Scott Maxwell | Dreamstime.com.

5b. What level of the drug (low, medium, or high) should Dr. Ryder give him? Explain your answer.

5c. In your own words, summarize how knowing someone’s TPMT DNA sequence could be used to determine what kind of medical care they should receive.

Postscript Dr. Ryder responded quickly to Laura’s drug reaction. She discontinued the drug while alternate treatment regimens were explored, and Laura’s condition began to improve.

 

 
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BI101 Unit 1 Experiment

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  • Read through the introductory materials below.
  • Open the Unit 1 Experiment Answer Sheet and complete the following Experiment exercises this unit:
    • Experiment 1 Exercise 1 – The Scientific Method (~30-45 min)
    • Experiment 1 Exercise 2A – pH of Common Materials (~30-45 min)
    • Experiment 1 Exercise 2B – pH and Buffers (~45-60 min)
  • Save your completed Unit 1 Experiment Answer Sheet and submit it no later than Sunday midnight CT.

The Scientific Method – Introduction

The Scientific Method is the basis for almost all scientific research. If you click on the Unit 1 Overview page, you can read about how the Scientific Method is conducted. You can also read about the process in your book on pp 14-17. One area of confusion often involves the difference between a hypothesis and a prediction. This is because many people use these terms interchangeably, but in fact, they are different. Here is how your book discerns the two:

Hypothesis – an answer to a question or explanation of an observation (p 14).

Prediction – an expected outcome if our hypothesis is correct; often worded as “if…then” (p15).

The purpose of this first exercise is to have you use the Scientific Method yourself. We will use the following web site. Be sure that you can access it and use it:

Bowers, N. 2013. Scientific Method Exercise (Links to an external site.)
When you are ready to begin, use the instructions in the Unit 1 Experiment Answer Sheet and work through the exercise.

pH of Common Materials – Introduction

This unit we are also learning about some of the chemistry that is important in biological systems, such as pH. Be sure you have read pp 32-33 in your book and our online lecture this unit before beginning this exercise. The pH scale ranges from 0 to 14; a pH less than 7 is considered acidic and a pH greater than 7 is basic. The pH scale is logarithmic, which means that a solution with a pH of 3 is ten times more acidic than a solution with a pH of 4 and a hundred times more acidic than a solution with a pH of 5.

Acids and bases are not necessarily a bad thing. Many of the materials that we handle and eat and drink everyday vary in pH. Some of these materials are safe to handle, such as “weak” acids (e.g., soda, coffee). Stronger acids (e.g., battery acid) and bases (e.g., ammonia) can be quite caustic and damaging. One way to measure the pH of liquids is to use pH indicator paper; paper that turns a particular color depending on the pH of the solution. Anyone with a swimming pool or hot tub is probably familiar with such paper.

When you are ready to begin, open the Unit 1 Experiment Answer Sheet and follow the instructions to complete this exercise.

Buffers – Introduction

As you saw in the previous exercise, the pHs of common solutions vary across the pH scale! Yet our body is constrained to work within a very narrow pH range. Small changes in pH can alter the function of biologically important molecules such as enzymes, by breaking hydrogen bonds and denaturing these proteins. For this reason, in most organisms (such as ourselves), pH is very closely regulated. pH can be kept relatively constant by the use of buffers, chemicals which can absorb or release hydrogen ions to maintain a relatively steady pH.

In most vertebrate animals, blood pH must be maintained between 7.35 and 7.45. There are several biological buffers that work to maintain this pH; one of the more important being the carbonic acid – bicarbonate system:

H2O + CO2 <–> H2CO3 <–> H+ + HCO3-

In the reactions above, the double headed arrows indicate that each step is reversible. If carbon dioxide (CO2) levels increase in our blood, it can combine with water to form carbonic acid (H2CO3), which can break down to form bicarbonate (HCO3-) and hydrogen ions. This would shift the pH towards the acidic end. If the acidity levels become too high, the whole process will reverse, such that hydrogen ions are removed and carbon dioxide is produced; thereby shifting the pH towards the alkaline end. This is only one example of a biological buffer; there are several other systems involved, but they all operate in a similar manner.

The purpose of this exercise is to help you understand the chemistry of buffers. Be sure that you have read through the material on pp 32-33 in your book and this unit’s online lecture on The Chemistry of Life. For this exercise, you will use the following website (be sure your speakers are on):

McGraw-Hill Education. No date. Buffers Animation. (Links to an external site.)

You may need to download and install a plugin to use this simulation, so test this simulation early in the unit in case you run into problems. When you are ready, open the Unit 1 Experiment Answer Sheet and follow the instructions there to complete this exercise.

WEEK 1 EXPERIMENT ANSWER SHEET Please submit to the Week 1 Experiment dropbox no later than Sunday midnight.

SUMMARY OF ACTIVITIES FOR WEEK 1 EXPERIMENT ASSIGNMENT

· Experiment 1 Exercise 1 – The Scientific Method

· Experiment 1 Exercise 2A – pH of Common Solutions

· Experiment 1 Exercise 2B — pH and Buffers

Experiment 1 Exercise 1: The Scientific Method

After viewing following video, answer the questions that follow:

Bowers, N. 2013. Scientific Method Exercise http://www.youtube.com/watch?v=8S7N_1xnYEE&feature=youtu.be

1. Write out four biological observations you made as you watched the video. Be specific about what you saw. These observations might deal with the habitat, season, flora, fauna, behaviors and interactions (2 pts).

2. Choose one or two of the observations above and write two questions you have regarding what you observed (2 pts).

3. Based on your observations or questions write two possible hypotheses that might explain your observation and/or answer your question (2 pts).

4. Write one prediction based on each hypothesis listed in Q#3 (2 pts).

5. What additional information might you need in order to design and conduct an experiment to test that one of your hypotheses (2 pts)?

Experiment 1 Exercise 2A: pH of Common Solutions

Be sure that you have completed your text book readings, have read through the online lecture and have read the introductory material for the Week 1 Experiment before starting. First, answer the following questions:

Questions

1. What is the definition of an acid? Your definition should include more than just a pH range. Provide one example of an acid. Cite your sources. (2 pts).

2. What is the definition of a base? Your definition should include more than just a pH range. Provide one example of a base. Cite your sources. (2 pts).

Procedure

A. Using your textbook, online lecture or other source, fill in Table 1 below. Be sure to complete your predictions BEFORE you look up the actual pH values.

B. Be sure to provide complete citations for the sources used to determine the actual pH values.

Table 1. Predicted and actual pH values and your explanations. You are only required to complete the first six; the others are optional. Use your textbook, online lecture or other source to determine the actual pH values (6 pts).

 

 Substance Predicted pH Explanation for Prediction Actual pH
1 Lemon juice      
2 Stomach acid      
3 Oven cleaner      
4 Antacid      
5 Pure water      
6 Orange juice      
Optional additional solutions
7 Sea water      
8 Vinegar      
9 Shampoo      
10 Soft drinks      
11 Tomatoes      
12 Battery acid      

Questions

1. Which of your substances tested are considered an acid (1 pts)?

2. Which of your substances tested are considered a base (1 pts)?

3. What surprised you most about your results in this activity (1 pts)?

Experiment 1 Exercise 2B: Buffers

Before beginning, answer the following question:

Question

1. What is a buffer and briefly, how do they work? Cite your source (2 pts)?

Procedure

Watch the following simulation and answer the questions after watching.

https://www.youtube.com/watch?v=ZLKEjXbCU30

Questions

2. Why does the green bar in the graph drop? Why does the purple bar in the graph rise? Explain what is occurring chemically (4 pts).

3. In the simulation shown, what happens to the pH in the beaker when HCl is added? How do you know this based on what you see in the graph (2 pts)?

4. What will happen to the pH if HCl is added after all of the acetate is used up? (1 pts)?

5. What is formed when sodium hydroxide is added and how does this affect the pH (4 pts)?

 

Week 1 Experiment Grading Rubric

Component Expectation Points
Experiment 1 Exercise 1 Demonstrates an understanding of the Scientific Method and an ability to apply it (Table 1, Questions 1-3) 10 pts
Experiment 1 Exercise 2A Demonstrates an understanding of pH and how it applies to your everyday life (Table 2, Questions 1-5). 13 pts
Experiment 1 Exercise 2B Demonstrates an understanding of pH and the effect of buffers (Questions 1-5) 13 pts
TOTAL  

 36 pts

Updated August 2017

 
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BioChemistry Test

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Question 1.1. Rank butane (CH3CH2CH2CH3), butanoic acid (CH3CH2CH2COOH), and pentane (CH3CH2CH2CH2CH3) in order of increasing boiling point. (From lowest to highest.) (Points : 3)

butane < butanoic acid < pentane        butane < pentane < butanoic acid        butanoic acid < pentane < butane        pentane < butanoic acid < butane

 

Question 2.2. Choose the equilibrium constant that indicates the greatest relative amount of reactant concentration at equilibrium. (Points : 3)

1.1 x 10–7        2.3 x 107        6.7 x 102        8.3 x 10–2

 

 

Question 3.3. Which of the following is the conjugate acid of NH3? (Points : 3)

NH2-        NH4+        HNO3        H3O+

 

 

Question 4.4. What volume of 0.200 M HCl is required to completely neutralize 50.00 mL of 0.150 M KOH? (Points : 3)

7.50 mL        50.0 mL        66.7 mL        37.5 mL

 

 

Question 5.5. The fluid mosaic model  proposes that (Points : 3)

membranes can move like a fluid.        proteins are embedded into the cell membrane.        materials that are fluid move across a membrane.        the composition of membranes includes a mosaic fluid

 

 

Question 6.6. The IUPAC name of the molecule below is                                        (Points : 3)

hydroxyl -2,4-dichlorocyclohexene        3,4-dichlorophenol        2,4-dichlorophenol        1,3-dichlorophenol

 

 

Question 7.7. Which of the following is the conjugate base of the acid, carbonic acid?  (Points : 3)

H2CO3        H2O        H3O+        HCO3–

 

 

Question 8.8. How many alkane constitutional isomers exist with the formula C5H12? (Points : 3)

2        3        4        more than 5

 

 

Question 9.9. The side chain of the amino acid tyrosine is shown here. The side chain is classified as ___. (Points : 3)

nonpolar        polar-acidic        polar-basic        polar-neutral

 

 

Question 10.10. Which of the following lipids is not derived from cholesterol? (Points : 3)

progesterone        thromboxane        cortisol        testosterone   51.Which is an α-amino acid?   *a)  b)  c)  d)

 

 

Question 11.11. Antacids may contain which ion to reduce acidity? (Points : 3)

Na+        CO32–        Al3+        Cl–

 

 

Question 12.12. In which of the following levels of protein structure can hydrogen bonding NOT play a role? (Points : 3)

primary        secondary        tertiary        quaternary

 

 

Question 13.13. What is the pH of a solution in which [H3O]+ is 2.2 x 10-12 M? (Points : 3)

2.34        4.54 x 10-3        11.66        8.42

 

 

Question 14.14. What level of protein structure is not disturbed by denaturing? (Points : 3)

tertiary structure        primary structure        secondary structure        quaternary structure

 

 

Question 15.15. The pH of a 1.25 x 10-3 M NaOH solution is: (Points : 3)

2.90        7.00        11.1        3.10        10.9

 

 

Question 16.16. What is the concentration of [H3O+] in an aqueous solution when the [OH-] is 5.2 x 10-9 M? (Points : 3)

1.9 x 10-6 M        5.7 M        1.0 x 10-14 M        9.8 x 10-9 M

 

 

Question 17.17. The element found in the center of the heme prosthetic group is ___. (Points : 3)

iron        sulfur        nitrogen        carbon

 

 

Question 18.18. The Ka for the reaction of acetic acid and water shown below is 1.8 x 10-5.   Which of the following statements is true at pH 7? (Points : 3)

there is much more acetic acid than acetate ion        there is more acetate ion than acetic acid        the concentration of acetate ion is equal to that of acetic acid        the pH is lower than pKa of acetic acid

 

 

Question 19.19. Which of the following statements is true about alkanes? (Points : 3)

alkanes contain polar bonds        alkanes are attracted to one another by London forces        alkanes are polar molecules        alkanes are unsaturated hydrocarbons

 

 

Question 20.20. The structure of glycerophospholipids contains (Points : 3)

a phosphate group, glycerol, three fatty acids, and a sugar molecule.        a phosphate group, glycerol, two fatty acids, and an alcohol molecule.        a phosphate group, a cyclic carbon ring, and variable numbers of fatty acids.        a phosphate group, a carbohydrate molecule, an alcohol, and fatty acids.

 

 

Question 21.21.  Kw, the equilibrium constant for the ionization of water by the equation below, is 1.0 x 10-14. What does that mean when we are considering pure water?  (Points : 3)

More ions exist than water molecules.        The majority of the molecules present are in the form of H2O.        The amount of water is the same as the amount of the ions present.        There will always be more hydronium ions present than water at equilibrium.

 

 

Question 22.22. Carbon must form how many bonds? (Points : 3)

1        2        3        4

 

 

Question 23.23. What is the function of nonsteroidal anti-inflammatory drugs (NSAID)? (Points : 3)

To interrupt the production of prostaglandins from arachidonic acid.        To interfere with the production of anabolic steroids.        To facilitate the production of cyclooxygenase.        To stimulate the production of leukotrienes.

 

 

Question 24.24. You produce 500 mL of a 0.001 M HClO4, which ionizes completely in water. What is the pH you should expect? (Points : 3)

pH = 0.5        pH = 3.0        pH = 2.7        pH = 500

 

 

Question 25.25. The α-helix and β-pleated sheet are both forms of the ___ structure of proteins. (Points : 3)

primary        secondary        tertiary        quaternary

 

 

Question 26.26. The ethylammonium ion, CH3CH2NH3+ has a pKa of 10.81. It reacts with water to form ethylamine, CH3CH2NH2 and H3O+ as shown below. Which of the following statements is true at pH 7? (Points : 3)

ethylammonium ion predominates        ethylamine predominates        the concentration of ethylamine equals that of ethylammonium ion        the pH is higher than pKa of the ethylammonium ion

 

 

Question 27.27. Which of the following is the conjugate acid of the bicarbonate ion, HCO3-? (Points : 3)

H2CO3        CO32-        CO2        H3O+

 

 

Question 28.28. A solution in which the concentration of H+ is greater than the concentration of OH- will (Points : 3)

have a pH greater than 7.0 and be basic.        have a pH less than 7.0 and be basic.        have a pH greater than 7.0 and be acidic.        have a pH less than 7.0 and be acidic.

 

 

Question 29.29. Whenever an equilibrium constant, Keq, has a value greater than 1, which of the following statements is true at equilibrium? (Points : 3)

The concentration of reactants is greater than the concentration of the products.        The concentration of products is the same as the concentration of reactants.        The concentration of the products is greater than the concentration of the reactants.        Relative composition of reaction mixture cannot be predicted.

 

 

Question 30.30. The term commonly used for a chain of amino acids 100 units long is ___. (Points : 3)

peptide        oligopeptide        polypeptide        centapeptide

 

 

Question 31.31. Which material would be effective for neutralizing a minor acid spill? (Points : 3)

soap solution        vinegar solution        baking soda        household ammonia

 

 

Question 32.32. One characteristic of basic solution is that (Points : 3)

the solution would turn litmus red.        the solution would have a slippery feel to it.        the solution would have a sour taste.        the solution would dissolve some metals.

 

 

Question 33.33. Give the correct IUPAC name for the following molecule:  (Points : 3)

3, 4-Dimethylpentane        2,3-Dimethyl heptane        2,3-Dimethylpentane        1,1,2-Trimethylpentane

 

 

Question 34.34. A Ka can be calculated for some chemical reactions. The Ka is (Points : 3)

the Keq for the reaction to the right.        the Keq for the reaction to the left.        the Keq for the dissociation of an acid.        the pH of a very weak solution.

 

 

Question 35.35. The equation: has the following equilibrium constant expression. (Points : 3)

 
 
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