What types of behaviors are considered high risk for acquiring sexually transmitted infections?

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As part of their commitment to “going green,” Layla and Steve Jackson lived on a small farm in rural northwest Pennsylvania. Steve chopped wood from their forest to burn in their Franklin stove, and about 25% of their electricity was generated by the wind turbines on top of their mountain. They raised almost all of their own food between their small apple orchard, huge vegetable garden, and a berry patch. The couple reared numerous sheep, a few pigs, and one dairy cow. These animals plus the rabbit, turkey, and deer Steve hunted more than covered their meat and milk needs. Although the young couple loved working their farm, to make ends meet financially, they also taught at the local high school. Layla was a 10th grade math teacher and Steve served as both the choral and band directors for grades 7–12. Unless the roads were icy in the winter, the “green team” biked the four miles to work every day. While this lifestyle kept them extremely busy, Layla and Steve felt great satisfaction knowing their carbon footprint was significantly less than that of the average American.

As Layla picked the green beans and weeded around the squash one July morning, she pondered how their lifestyle would change in November when their first child was due to be born. She was pleased to be able to raise their child in the unpolluted environment of their country farm and nourish him with homegrown foods free of the pesticides and preservatives found in many commercially produced items. “Of course,” Layla said to herself while patting her belly, “I think we’ll have to break down and drive a little more this winter. You’ll be a bit too small for my baby bicycle seat.” As if on cue, the baby started “dancing.” Laughing, Layla collected the baskets of produce she had harvested and headed to the kitchen to start making lunch. After rinsing the fresh-picked fruits and vegetables, Layla used her garden’s bounty to assemble a delicious salad and homemade strawberry shortcake with cream from Josie, their cow. Later that afternoon, the couple went to Dr. Schneider’s office for Layla’s monthly prenatal examination. They watched with amazement as the obstetricianused ultrasoundto measure the baby’s growth, confirming that Layla was 23 weeks pregnant. Dr. Schneider pointed out different features of their developing child. They saw a tiny beating heart and learned it was time to paint the nursery blue!

Layla’s pregnancy progressed normally until her next appointment at 27 weeks gestation. Dr. Schneider was surprised to find Layla hadn’t gained any weight in four weeks. “At this stage of your pregnancy, you should be gaining about 0.5 to 1 pound per week,” Dr. Schneider said with concern. “Are you eating enough nutritious foods?”  Layla was happy to report a healthy appetite that she regularly indulged with the foods she and Steve raised. “I bet it’s the extra exercise I’m getting,” Layla explained. “I’ve been canning produce as fast as I can harvest the garden and orchard. I’m up and down the hillside a dozen times a day hauling a full bushel basket, so I bet I’m just burning off the calories with my gardening.”  Dr. Schneider cautioned Layla not to be lifting heavy baskets and encouraged her to add an afternoon snack to her usual diet. “I want to see you in two weeks to be sure your weight gain is back on track,” Dr. Schneider ordered. Exactly one week later, Layla called and scheduled an urgent appointment. For the previous 48 hours, Layla had experienced significant vomiting and diarrhea. By the time she arrived at Dr. Schneider’s, Layla was weak and slightly dehydrated. Frantic, Layla reported a decrease in fetal activity. Dr. Schneider admitted Layla to the hospital for IV fluids and prescribed medication to ease her GI distress.

  1. What infections manifest with these symptoms? Are any specifically associated with pregnancy?

An hour later Dr. Schneider performed an ultrasound to check on the progress of Layla’s developing son and was shocked to see no fetal growth since her week 23 examination. In the morning, Dr. Schneider arrived at the hospital early to examine Layla and her baby. Steve was asleep in a chair and Layla sat up in bed weeping gently. She hadn’t felt the baby move since midnight. Dr. Schneider confirmed Layla’s worst fears with another ultrasound, which showed no fetal heartbeat. Labor was induced to deliver Layla and Steve’s 28-week-old stillborn son. A fetal autopsy revealed elevated titers of toxoplasmosis antibodies, hydrocephalusand brain lesions.

  1. Describe the causative agent of toxoplasmosis. Outline the life cycle of this microorganism.

A week later, Layla and Steve met with Dr. Schneider to review the autopsy report and answer their long list of questions. “So, I got toxoplasmosis and that’s why I was so sick…and then I made the baby sick too,” Layla said dismally.

  1. Were Layla’s symptoms consistent with toxoplasmosis? Describe the usual signs and symptoms of this infection. What is a secondary infection?

“No,” Dr. Schneider replied, “not exactly. Your GI symptoms were coincidental and represent a secondary infection. They simply alerted us to the problem with the baby’s growth. It does; however, appear you’ve been infected with toxoplasmosis and the pathogen crossed the placenta to affect your baby. “Wait a minute,” Steve interjected. “How did Layla get toxoplasmosis? I’ve heard about this disease. Pregnant women get it from changing litter boxes. We don’t have a pet cat. In fact, we don’t even have strays in our barn!”

  1. Are litter boxes a source of pathogen transmission? Explain.
  2. What are the most common means of toxoplasmosis transmission? Based on this information, was Layla at high risk for infection? How can toxoplasmosis be prevented?
  3. What is the prevalence of toxoplasmosis?

“Dr. Schneider, was there any way to diagnose and treat my infection that might have saved our baby?” Layla asked. “There are different diagnostic tests for toxoplasmosis, but they aren’t routinely run in a prenatal panel in the U.S. unless we have reason to suspect infection,” Dr. Schneider explained. “If a pregnant woman is infected, several treatment protocols are available, but the benefits must be carefully weighed against the risks since the likelihood of transmission and fetal damage varies with the gestational age of the mother seroconversion

  1. How is toxoplasmosis typically diagnosed? What challenges are associated with interpreting test results? How can fetal infection be determined?
  2. Describe the principal treatment protocols for toxoplasmosis infection in a pregnant patient. Indicate the pros and cons of each treatment. When is the best time during the course of Toxoplasma gondii infection to administer treatment to a patient?
  3. Explain the correlation between the gestational age of maternal seroconversion for toxoplasmosis and the risk of fetal infection.
  4. What signs and symptoms are expressed by neonates with congenital toxoplasmosis? What symptoms are expressed by infected children within the first year of life? What is the miscarriage rate associated with fetal toxoplasmosis?

“Now that I’ve been infected with toxoplasmosis, do I need to be treated? If I’m cured can we still have other children, or will I infect them too, causing another miscarriage?” Layla asked hopefully. “Not to worry,” Dr. Schneider consoled the young couple. “You’ve suffered a devastating loss, but I’m confident you’ll soon be parents.”

  1. Is it necessary to treat Layla for toxoplasmosis? Can she have subsequent children without risking their infection?

Anderson, R. et.al. Case study in microbiology: A Personal Approach, Publisher: John Wiley & Sons Copyright year: © 2006.

Case Study # 4

Sex, Drugs and Rock and Roll

Jim was a police officer and his wife Barb a nurse at the hospital that handled most of the city’s poor. It was inevitable that their paths would occasionally cross during work. Tonight, they were both at a community outreach meeting concerning the problems caused by the increase in crystal meth use. Methamphetamine, or crystal meth, is a powerfully addictive stimulant that has an intense euphoric

effect.  Jim saw its effect when chronic crystal meth users would embark on binges of constant meth use. The results were universally disastrous––intense paranoia, visual and auditory hallucinations, and violently out-of-control behavior. Barb saw another side of abuse of the drug. Crystal meth use has a potent effect of increasing the sex drive. As a result, crystal meth users were more likely than others

to engage in high-risk sexual behaviors and have more sexual partners than nonusers. Barb had seen a significant increase in cases of gonorrhea in general, and increases in syphilis and HIV disease among gay men. Long-term users of crystal meth build up a tolerance to the drug. As a result, many choose to inject the drug to continue to get high. Not unsurprisingly, intravenous drug use increases the spread of HIV as users share needles (and therefore exchange small amounts of blood). At counseling programs designed to help HIV-positive gay and bisexual men who use crystal meth, about half had injected meth during the last year. Neither Jim nor Barb was the type to sit back and hope for the best. They had much invested in their community where their children went to school. Both were consistent volunteers. Jim already coached soccer and led scouts. Barb was active at their church and volunteered to help students with reading and math at school. At the end of the meeting, both took part in the discussion and planning sessions on how to help the community stem the problems caused by widespread crystal

meth abuse.

  1. What types of behaviors are considered high risk for acquiring sexually transmitted infections?
  2. What pathogens are responsible for causing these STI’s? Describe each.
  3. What are the clinical signs and symptoms of gonorrhea? Compare them to those caused by syphilis.
  4. What other STIs would you expect to be increased following an increase in high-risk sexual behaviors and an increase in sexual partners?
  5. In general, how can the spread of STIs be reduced?
  6. Are the activities needed to prevent or reduce the spread of STIs likely to be followed by crystal meth users?
  7. What recommendations would you make to Jim and Barb’s community group to help reduce the spread of STIs among the crystal meth users?

Discuss how this gelatin+/-pineapple experiment relates to the material that we learned this week

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Lab 4 1

Lab 4: Molecules of life This week, we are learning that the structural and functional differences between each of the 4 macromolecule groups (carbohydrates, proteins, lipids, nucleic acids) are very important in controlling the structure and function of biological systems such as cels. In this week’s lab, you will visualize first-hand how exposing the molecules of life to varying environments (temperature, pH, etc) dramatically impacts structure and function. Part 1: Heat and Macromolecule Structure and Function As we’re learning this week, denaturation occurs when the molecules of life are exposed to environmental conditions outside their normal range; however, the level and severity of denaturation may (and does) vary depending the specific macromolecule and the environmental conditions. This will be directly observed in our experiment below. In this experiment, we’ll be comparing Coke to Diet Coke. Specifically, regular Coke is sweetened with sugars (carbohydrates) such as monosaccharides glucose and fructose, and also the disaccharide sucrose (glucose+fructose), while Diet Coke is sweetened with a protein- based compound called aspartame (NutraSweet is the brand name; made by linking together two amino acids, aspartic acid and phenylalanine) which tastes sweet, but does not contain the caloric value of sugars. Materials

 1 can/bottle Diet Coke

 1 can/bottle Regular Coke

 Access to heat: Microwave and Microwave safe cup or stovetop and saucepan. Experimental Set Up: A. Taste each, the Coke & Diet Coke. Record your observations regarding how each taste in the

table below. B. Carefully heat some Diet Coke and some regular Coke (separately). To do this, you can

• boil each on a stovetop for ~ 2-5 minutes, or • microwave some of each to boiling (make sure heat is sustained for 2-5 minutes).

C. Allow each to cool (it is ok to refrigerate or add ice). D. Taste each again*. Record your observations regarding how each tastes after heating in the

table below.

Coke Observations Regular Coke Diet Coke

Before Heating

After Heating (and cooling)

Lab 4 2

*Note- while the solution(s) may taste different after heating, neither is more harmful to drink after heating than it was before heating. When you are finished, answer the following questions: 1. Briefly describe the taste of the regular Coke and the Diet Coke both before and after

heating. Did the taste of either change after heating, and how? 2. What do the results of the Coke/Diet Coke heating experiment tell you about the relative

denaturation sensitivity and process of carbohydrates versus proteins? Explain your answer.

3. Discuss how this Coke/Diet Coke heating experiment relates to the material that we learned this week. Use specific examples.

Part 2: Pineapple Jell-O For this activity, you’ll need some basic equipment outlined below. Plan ahead, making jello takes time (it needs to set in the fridge). You won’t be able to start this right before the lab is due 😉 Materials

 Jell-O Gelatin, 2 identical packages (regular not sugar/fat free, not pudding, not premade; Gelatin must be listed as an ingredient), any flavor.

 Fresh Pineapple (< 1/2 cup is all you will need)

 Canned chunked pineapple in juice

 Large bowl (or container) for mixing the finished Jell-O

 4 smaller containers at least 3 inches tall (ideally clear, glass or plastic) (ex: juice glass)

 Water

 Refrigerator

 Knife and cutting board

 Tape and markers for making labels

 Stopwatch/timer

 Ruler (metric is best, 12 inch/30cm) Experimental Set Up: A. Label your 4 clear containers as follows

 1: Fresh, 2: Fresh, 3: Canned, 4: Canned B. Prepare the gelatin by following the directions on the package. SAVE THE BOX. C. Pour equal amounts of liquid gelatin into each of the 4 numbered containers (see image). D. Place the gelatin into the refrigerator to set. Leave in the refrigerator until fruit is prepared. E. After the gelatin is fully set (it is now solid, jello), prepare the fruit. Remove all juice, and cut

Lab 4 3

4 pieces of pineapple (2 Fresh and 2 Canned) each the size of a quarter. Make sure that the pineapple chunks are all approximately the same size and shape.

F. Remove all the gelatin containers from the refrigerator; from now on you will be working at room temperature.

G. Measure (in centimeters) the length of solid gelatin in each container (line ruler up alongside container) Record this measurement (at time 0; solid gelatin depth) in the table provided below (or on a separate piece of paper).

H. Place a piece of pineapple on the surface of the gelatin as appropriate (fresh pineapple to containers 1 and 2, canned pineapple to containers 3, and 4), and start the timer.

I. Every 15 minutes for the next 2 hours:

 Examine/observe the appearance each gelatin + pineapple treatment.

 Measure (in centimeters) the distance the fruit has moved into the gelatin

 Record your measurements and describe your observations for each container in the table provided (or on a separate piece of paper).

J. Use this distance migrated to quantitatively evaluate each treatment.

 For example, if you start with 8cm solid gelatin in your container and: after 1 hour the pineapple had moved through 5cm  62.5% (5/8cm*100) of the gelatin, and after 2 hour the pineapple had moved through 7cm  82.5% (7/8cm*100) of the gelatin.

Note: if desired, and pending clean handling of samples and measurement materials, the Jello+/-Pineapple treatments are safe to eat at this point. Make sure you record your observations before snacking! Experimental Fruit Depth Optional Data Collection Table:

Expired Time

(h:min)

Container 1: Fresh Container 2: Fresh Container 3: Canned Container 4: Canned

Distance Description Distance Description Distance Description Distance Description

0

solid gelatin depth

solid gelatin

depth

solid gelatin depth

solid gelatin

depth

0:15

0:30

0:45

Lab 4 4

1:00

1:15

1:30

1:45

2:00

When you are finished, answer the following questions: 4. When you were setting up the gelatin+/-pineapple experiment, explain why was it better to

have two containers for each condition instead of only one?

5. Did the gelatin+/-pineapple experiment include a control? If so, what was it? If not, what could have served as a valid control for this experiment?

6. Briefly summarize the results of the gelatin+/-pineapple experiment. What were the effects of fresh versus canned pineapple on the gelatin? Include a description of each treatment, along with the relative % migration for each pineapple after 1 hour and 2 hours each.

7. Review the preparation instructions on the gelatin box. What do you notice about the

manufacturer’s recommendations regarding the addition of fruits to gelatin-based desserts? Why do you think this is? How does that relate to the gelatin+/-pineapple experiment?

8. Discuss your results for the gelatin+/-pineapple experiment treatments 1 and 2, versus treatments 3 and 4. What happened? What molecular component of the pineapple could be responsible for converting the gelatin from a solid to a liquid? Explain your rationale.

9. Using what you’ve learned this week about the structure and function of the molecules of

Lab 4 5

life, discuss your results for the gelatin+/-pineapple treatments 3 and 4. What could be different between the canned and fresh pineapple (hint: during the canning process, pineapples are heated to a high temperature for sterilization purposes).

10. Note that in the instructions for the Jello and Pineapple experiment, the material specifically require Gelatin based Jello. The reason for this is because the experiment does not work with gels that are solidified with molecules other than gelatin (Dr. Pangle personally verified that premade “Snack Pack” pre-prepared gel cups, lacking gelatin, do not work with this experiment). What does this tell you about the chemical reaction that occurs between whatever was in the pineapple and it’s substrate? What was in the pineapple anyway?

11. Discuss how this gelatin+/-pineapple experiment relates to the material that we learned this

week. Use specific examples.

12. Let’s examine another example of macromolecules and structure and function. The composition of an egg white is 90% water and 10% protein (primarily a storage protein called Albumin that will be used to make all the proteins of the developing chick). Based on what you know about proteins, what happens to the albumin when you cook and egg, why?

Solvents and cells

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Lab 5 1

Lab 5: Solvents and cells

Part 1: Chemistry of Molecules Read/watch the provided resources and take notes, applying the information to what we learned this week. CO2 and Soda: https://www.youtube.com/watch?v=HFCeV5BVBh0 Dissolving M&Ms: https://www.youtube.com/watch?v=umJmRaG6v80 When you are finished, answer the following questions: 1. You are having a debate with a friend about the science behind the Diet Coke and Mentos phenomenon. Your friend thinks that since the volume of matter after the experiment (the big mess) seems to be more than what was originally present in the individual components (soda/Mentos) before they were combined, that the “explosion” is the result of carbon dioxide being produced (made) by the reaction. Is this true? Does the amount of carbon dioxide increase through this reaction? Use what you’ve learned this week to verify or debunk your friend’s argument.

2. During the M&Ms experiment, why did the scientist emphasize that each of the treatments in this experiment needed to be stirred the same say, for the same length of time?

3. For the M&M experiment, name and describe the chemical property that is demonstrated by both the sugar and the candy coloring in the shell of an M&M that permits dissolution in the water, but not in the oil.

4. In your own words discuss this quote. Was Jamf mistaken in his understanding of the relative strengths of ionic and covalent bonds? Explain why/why not (in your own words!).

5. The scientific field of organic chemistry is based entirely on studying the chemical structure and reactivity (bonds and chemical reactions) of carbon containing molecules. Based on what you learned in class this week, discuss why carbon is so important that entire fields of study are dedicated to understanding and applying it.

https://www.youtube.com/watch?v=HFCeV5BVBh0
https://www.youtube.com/watch?v=umJmRaG6v80

Lab 5: Follow the instructions and complete the assignment below. Submit your answers through the Lab 5 Assignment on Blackboard.

Lab 5 2

Part 2: A Picture is Worth a Thousand Words This unit we learned about cells, their structure, and how they carry out the processes of life. We know that there are size restrictions that prevent living cells from being too small or too large. However, the rules that govern cell size may be more complex than scientists originally thought. The existence of ultra-small living cells has been debated for two decades. This debate was settled in February of 2015, when researchers from the U.S. Department of Energy’s National Laboratory at UC Berkeley obtained the first microscopy images of ultra-small bacteria- about as small as life can get. Follow this youtube link to view the research images/reconstructed videos of the cell structure: https://www.youtube.com/watch?v=ofNrtg-FpSc; primary article may be provided upon request. This part of the lab will focus on a popular media ScienceDaily article that summarizes the researchers’ findings. However, before we investigate these ultra-small nanobes, it is important that we fully comprehend the history and scientific impact behind this debate. For this, you’ll need to read the following extract: “In 1996, researchers published a description of a meteorite that fell from Mars, which sparked a long and complicated debate over the existence of what they called ‘nanobacteria’, later also described as nanobes. Various teams argued over whether life, theoretically, could live to be that size, but the debate didn’t really get anywhere because no one really had any evidence for either side. One side said all the things needed for life – DNA, RNA, proteins and solvents – couldn’t actually fit inside a cell that small, while others said life could be that small, but just in a starved, inactive state. Researchers argued over the theoretical limit for how small a cell could get in diameter and volume, and one team even reported finding some marine nanobes, but lacked direct microscopic evidence to prove they fit inside the size range to classify them as such. But now, such bacteria found in some Colorado groundwater have been imaged, and these things are undeniably tiny – several times tinier than several estimates for the lower size limit of life on Earth, in fact. And as difficult as it is to see them, the researchers think they could actually be quite common.” http://www.sciencealert.com/new-images-reveal-the-tiniest-known-life-forms-on-earth Next, click the link to read the article describing researchers’ findings and use this information, along with what you learned this week to answer the provided questions. https://www.sciencedaily.com/releases/2015/02/150227181339.htm When you are finished, answer the following questions: 6. The image at the beginning of the ScienceDaily article shows and describes the visible structure of the cell, and the authors state: “The cell has a very dense interior compartment and a complex cell wall.” As you remember from your readings, not all cell types contain a cell wall. What kinds of cells, other than bacteria, would you expect to possess a cell wall? List the

https://www.youtube.com/watch?v=ofNrtg-FpSc
http://www.sciencealert.com/new-images-reveal-the-tiniest-known-life-forms-on-earth
https://www.sciencedaily.com/releases/2015/02/150227181339.htm

Lab 5: Follow the instructions and complete the assignment below. Submit your answers through the Lab 5 Assignment on Blackboard.

Lab 5 3

functions that this structure provides for these organisms. How do organisms that don’t have a cell wall execute these same functions? 7. The image at the beginning of the ScienceDaily article shows and describes the visible structure of the cell, and the authors state: “The darker spots at each end of the cell are most likely ribosomes.” Of all the different structures that could exist within a cell, why do you think that the authors think that these are ribosomes? (Hint: think about the types of cellular structures that are/aren’t found within bacteria, and what ribosomes do, and the importance of that job, within a cell.)

8. Interestingly, the ScienceDaily article states: “images also revealed dividing cells, indicating the bacteria were healthy and not starved to an abnormally small size.” This statement implies that in order for cells to divide they must be “healthy”. Discuss the requirements that a “healthy” eukaryotic cell must meet before it will under cell division. What are the consequences if a eukaryotic cell divides even if these requirements are not met? 9. The ScienceDaily authors state: “About 150 of these bacteria could fit inside an Escherichia coli cell and more than 150,000 cells could fit onto the tip of a human hair”. To provide you with some context so that you can really understand this statement: the spherical diameter of a

typical Escherichia coli cell is 1.3 m (micrometers), and the spherical diameter of these new

ultra-small bacteria is ~0.23 m. Compare the SVR of these new ultra-small bacteria to that of a typical E. coli cell (Hint: you need to calculate the SVR for each), which organism has a larger SVR, does this make sense in the context of the size of the cell? 10. Throughout the ScienceDaily article, the researchers studying these tiny bacteria acknowledge the challenges that such small cells face when it comes to performing the basic functions of life, and the additional challenges that limit our ability to study such small organisms. This makes sense, considering that previously calculated theoretical minimum diameter of a cell was established (and generally accepted by respected scientists and experts

in the field) to be 0.250-0.30 m. The authors say, “There isn’t a consensus over how small a free-living organism can be, and what the space optimization strategies may be for a cell at the lower size limit for life.” Why, before this, did scientists think that living cells couldn’t be much smaller than this lower limit (why is it that when a cell is too small, that it “can’t” survive)?

11. Choose another statement/quote from this article (or the other summary or the original research paper) and discuss how it relates to the material that we learned this week. Be sure to use specific examples (and your own words).

Chemistry important in biological systems

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How to Proceed

  • 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:

Glencoe/McGraw Hill. No date. The Scientific Method
http://www.glencoe.com/sites/common_assets/science/virtual_labs/ES01/ES01.html  (Links to an external site.)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.

We will use a virtual lab to examine the pH of common solutions that you might have around the house. You will use the following website; be sure you are able to access and use it:

Glencoe/McGraw Hill. No date. pH of Common Solutions
http://www.glencoe.com/sites/common_assets/science/virtual_labs/E22/E22.html  (Links to an external site.)Links to an external site.

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
http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/buffer12.swf  (Links to an external site.)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.

Unit 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