Lab 1 Characteristics of Life

Transcription

1 Lab 1 Characteristics of Life Name Biology 3 ID Number Section 1 - Observing Nature Section 2 - Organizing and Analyzing Data Section 3 - Using the Compound Microscope Section 4 - Qualities of Magnified Images Section 5 - Measuring Objects through the Microscope Section 6 - Characteristics of Life - Organization Section 7 - Characteristics of Life - Metabolism Section 8 - Characteristics of Life - Homeostasis Section 9 - Characteristics of Life - Responsiveness Section 10 - Characteristics of Life - Reproduction Section 11 - Characteristics of Life - Adaptation Objectives After completing the orientation and the first lab, you should be able to: 1. Determine the length of an object using the appropriate metric unit (cm, mm or m) 2. Understand how to convert the various metric units (convert cm to mm, mm to m, etc.) 3. Recognize the difference between qualitative and quantitative observations; direct and indirect observations. 4. Recognize the difference between point graphs and histograms and know when to use each appropriately. 5. List and define the characteristics of life (organization, metabolism, homeostasis, responsiveness, reproduction and adaptation). 6. Calculate the mean and range from a set of data and be able to estimate the mean by examining a normal distribution. 7. Recognize the names and functions of the parts of a microscope (iris diaphragm, nosepiece, scanning objective, low power objective, high power objective, ocular, mechanical stage, coarse focus and fine focus). 8. Measure the size of an object on the compound microscope using the micrometer scale on scanning, low and high power. 9. Calculate the total magnification when particular objective lenses are in place. (objectives continue on next page) 1.1

2 10. Recognize the appearance and functions of the plant cells examined cortex, epidermis and xylem cells. 11. Describe and give examples of the three types of adaptations physical, behavioral and physiological. 12. Define the following terms: sampling bias, random sample, binocular, inversion, magnification, field diameter, glass slide, cover slip, symmetry, starch, asexual, sexual and gamete. Section 1 - Observing Nature Begin the computer program and fill in the sections of the lab as you are directed. During the Orientation, you were introduced to two types of observations. Record the definitions and give an example of each: Qualitative observation: Quantitative observation: Most of the time in this class you will be making direct observations, where you can actually see the object under study. But in some cases scientists must rely on indirect observation in which you can t actually see the object in question, but must rely on other evidence. At the demo table, you will find two boxes labeled A and B. Shake each to see if you can guess what s inside of each: Box A contains: Box B contains: 1.2

3 Section 2 - Organizing and Analyzing Data Recall the metric units for length you were introduced to in the Orientation exercises centimeters (cm), millimeters (mm) and micrometers ( m). Unit Symbol Helpful Translation Useful Equivalents 1 meter m meter = a measure 100 cm 1000 mm 1 centimeter cm centi = 100 1/100 of a meter 10 mm 1 millimeter mm milli = /1000 of a meter 1 /10 of a cm 1 micrometer (or micron) m micro = million 1/1000 of a mm 1000 m in a mm Once you have answered the practice questions on the program, try these conversions: 180 mm is equal to cm 4.3 cm is equal to mm 2000 m is equal to mm 1.23 mm is equal to m Now we will use these metric units to collect some data about a living organism, a local tree species. Go to the demo table and collect a random sample of 20 leaves from the box and take them back to your booth. It is important that you pick the leaves randomly, because if you picked through the leaves and selected only the largest leaves or the smallest leaves, this would introduce sampling bias, which would mean the data were not a true representation of the variety of leaf sizes. Measure each leaf to the nearest 0.1 cm and record the data below: Are these qualitative or quantitative observations? Direct or indirect observations? 1.3

4 Complete the graph below to represent your leaf data. Notice that we are grouping the data into size categories, and therefore this is a histogram of the data. For each leaf size, shade in a single box of the graph in the appropriate size category. You will have a total of 20 shaded boxes when you are done, and a graphical representation of your data. Another way to represent data is by calculating two simple statistics, the mean (or average) and the range. The mean (we use the symbol x ) is calculated by adding all the data and dividing by the number of observations. For example, you measured the lengths of 20 leaves, so you will add all the lengths and then divide by 20. Mean leaf length = cm (round this number off to the nearest 0.1 cm) The second statistic, the range, is stated as the smallest value and the largest value of a set of data. This gives us a record of the extremes of values. Range of leaf lengths = cm to cm (find the smallest and largest leaf) Often when we measure biological objects, we find that the data falls into what we call a normal distribution. This is data that is balanced in both high and low values. A nice quality of this data distribution is that we can quickly estimate the mean by looking at the central value. 1.4

5 Estimate the average height of men from this normal distribution: cm Remember that the vertical axis shows how many men are in that height category, and the horizontal axis shows their actual height in centimeters. What is the range in height of these men? cm to cm. Section 3 - Using the Compound Microscope Before we use the microscope, familiarize yourself with the parts: The Binocular Compound Microscope 1.5

6 To begin, identify the coarse and fine focus knobs. Practice moving the stage up and down with the coarse focus. Move the stage down to its lowest position. Never force the knobs farther than they easily move. Find the nosepiece with the three objective lenses. Practice rotating the lenses into position. It should rotate easily and you should feel a slight click as each one comes into position. Leave the shortest lens, known as the scanning (4x) lens in position over the stage. This is always the lens you will start with when looking at any slide specimen. The other two lenses are called low (10x) power and high (40x) power and we ll get to them in a little while. Find the mechanical stage knobs which hang down from the stage. These knobs allow you to precisely move the slide from side to side. Now you are ready to view a slide. Find the Letter i slide in the blue slide box at your booth. As you hold the slide, notice that the label is on the left and a small piece of newspaper has been glued underneath a small square cover slip to the right of the label. The piece of newspaper is what you will examine under the scope. Make sure the microscope light is on. These scopes have a main light switch, (on the side of the base) and an intensity rheostat (a black wheel next to the switch). If you have turned on the scope and don t see any light, check the intensity adjustment rheostat wheel. Now place your slide on the mechanical stage by gently moving the stage clip lever out of the way. Place the slide flat on the stage, slide it into the frame, and gently move the clip slowly towards the slide until it just touches the corner of the glass slide, as shown in the drawing below. Do not let it snap against the slide and never place the clip on top of the slide! Correct position of a slide on the stage (as seen from the front of the microscope) Now you can use the mechanical stage knobs to move the slide around. Move the slide so that the little piece of newspaper is over the circle of light coming through the bottom of the stage. (You can do this by looking from the side of the microscope instead of through the lens - in fact, it s easier that way). 1.6

7 The two lenses at the top of the scope are called the oculars and since this microscope has two, this is known as a binocular scope. You should adjust the distance between the oculars by holding the base of each ocular and gently pushing them together or pulling them apart to match the distance between your eyes. You should see just one circle of light. Both eyes should be open and relaxed, as if you were looking through a pair of regular binoculars. The stage should already be in its lowest position, so start moving the stage slowly up with the coarse focus knob as you look through both oculars. You won t see the letter i until the stage is almost at the top. Stop when you see the letter i, then use the fine focus to sharpen the image. If the stage reaches the top and you still don t see anything, lower the stage, recenter the little piece of newspaper over the circle of light and try again. If you see the i is upside down, congratulations! You ve set up your scope correctly! Once the letter i is in focus, it is time to adjust the amount of light with the iris diaphragm and the rheostat adjustment. Practice changing the intensity of light as you look through the scope. Center the letter i under your field of view and switch to low power (the medium length lens) by rotating the objective into place (until you feel the click). Focus again with fine focus. The nosepiece holds the, and objective lenses. Which objective lens do you always start with? Which objective lens is more powerful, low power or scanning? Ask the lab instructor to come over and check your microscope. If everything is correct, they will initial the box below. Before you call them over, check the following: Is the slide correctly positioned in the stage frame? Is the low power objective in place and the letter i focused? Instructor signature: Is the light nice and bright? Now we will look at the letter i using the most powerful lens, high power. With the slide still focused on low power, rotate the nosepiece so that the high power lens clicks into place. It is very important that you use only fine focus whenever you are using the high power lens! You may need to turn up the light to see any detail. If you don t see anything, move the low power lens back in place, center the letter i in the exact middle of the field of view, and try again. At this point, if you were finished looking at the specimen, you would place the scanning lens back in place and lower the stage. But if you are continuing on to the next section, leave the Letter i slide on the stage and we will use it to complete the next exercise. 1.7

8 Section 4 - Qualities of Magnified Images One of the properties of microscope lenses is that the image that you see is inverted (upside down) and backwards from the orientation you may have expected when you put the slide on to the stage. Focus once again on the entire letter i using the scanning lens. Look at the slide from the side of the scope is the letter i right side up? And now look through the microscope. Is it inverted? Now looking at the stage from the side, move the stage very slightly to the left. Now look through the scope as you continue to move the slide. Which way does the slide appear to move, left or right? Keep these optical qualities in mind as you search slides for specimens. With three different objective lenses, we have a large range of magnifications. Find the magnification power printed on each lens (the number is followed by an x ) and fill in the values below. Then calculate the total magnifications by multiplying the power of the ocular lens with each objective. ocular lens x objective lens = total magnification Scanning lens in place x = Low power lens in place x = High power lens in place x = What color stripes does this lens have on your microscope? 1.8

9 This drawing of a microscope slide shows roughly how much of the slide you re able to see with each objective in place. Notice that the low magnification of the scanning lens shows a large area. The high power lens, however, shows just a tiny part of the slide. Use a ruler to approximate the field diameter of each power on the drawing above. The field diameter is the circle of light you re able to see with each lens in place. Express your values in the appropriate metric unit: Estimate of the scanning field diameter: Low power field diameter: High power field diameter: Because of these greatly different diameters, which objective lens is always the best when you start looking for a small object on a microscope slide scanning, low or high? The measurements you determined from the slide are estimates that you probably expressed in cm or mm. The numbers below are the actual values for these lenses and we can now express these values in our smallest metric unit, the micrometer ( m). Convert the values below into micrometers (remember there are 1000 m in a mm): Scanning field diameter is 5 mm = Low power field diameter is 2 mm = m m High power field diameter is 0.5 mm = m Are these actual values close to your estimates that you measured with the ruler? 1.9

10 Section 5 - Measuring Objects through the Microscope Now we can practice using these extremely small units, the micrometers, to measure some objects in the microscope. The microscope has a micrometer scale imbedded in the right ocular lens. You can look through the scope to see this scale, even without a slide in place. Make sure you are using both eyes when you look through the scope. Notice there are divisions marked on the scale as shown below: Micrometer Scale Although this scale looks like a ruler, it is not. The divisions will change in size as you change lenses. For example, if you were to see something like this object using the scanning lens: The object is 10 divisions in length multiplied by the conversion factor for the scanning lens, which is 25 µm. 10 x 25 µm gives us a true size of 250 µm If the object below were seen with the low power lens: The object is 15 divisions, but now we must multiply by 10 µm since we are using the low power objective. 15 x 10 µm, or 150 µm is the true size Try this one on high power: divisions x µm = 1.10

11 Now place the letter i slide on the microscope stage and focus using the scanning objective. Move the dot of the letter i carefully so that it is directly under the micrometer scale in the microscope and the edge of the dot touches the 0 of the micrometer scale. Dot on scanning: Draw the relative size of the dot on this micrometer scale as it appears in your microscope. Estimate the number of divisions and convert this value into µm to determine the actual size of the dot: Dot on low power: Now center the dot and switch to the low power objective. Line the dot up under the arrow and draw the relative size of the dot on the scale shown here. Determine the size of the dot: If we were to try to measure the dot with high power, the dot would go beyond the limits of the micrometer scale. So this time we will use the field diameter to estimate its size. This circle represents the field diameter of the high power lens. Focus the dot of the letter i on high power and draw the approximate size of the dot within this high power field diameter. If you lose the dot, go back to low power and make sure the dot is in the exact center of the field of view before you rotate the high power lens into position. What was the high power field diameter that you calculated earlier? µm Make a rough estimate of the size of the dot: µm Have the lab instructor check your measurements and initial the box: 1.11

12 Section 6 - Characteristics of Life - Organization The first characteristic of life that we will examine is the trait of organization. In living organisms we can often see organization in the overall pattern which we refer to as symmetry the balance of structures. To examine the cellular level of organization, find the slide labeled Ranunculus root in your blue slide box. Remember to start with the scanning lens in place before you begin and place the specimen over the circle of light. Using the micrometer scale, estimate the diameter of the entire root: Is this a qualitative or quantitative observation? How many different types of cells do you estimate are in the root cross section? Is this a qualitative or quantitative observation? Keep the slide on the microscope for the next section. Section 7 - Characteristics of Life - Metabolism Define metabolism: Although we can t view energy directly, we can look at some cells that are involved in storing energy for a plant. In plant roots, this region of cells is called the cortex and these cells store a critical molecule called starch. Starch is the compact form of hundreds of sugar molecules. Examine the Ranunculus root slide again on scanning power. The outermost layer of cells is a protective layer called the epidermis. We will examine the cortex cells just inside this surface layer. Change to low power and look for cortex cells. These cells contain starch grains, which are generally a lavender color. Use high power for the drawing below. Draw two or three cortex cells using high power Label one of the starch grains 1.12

13 Section 8 - Characteristics of Life - Homeostasis Homeostasis is the maintenance of a constant internal environment, despite changes in an organism s external environment. Throughout the day, plants maintain their shape by carefully controlling the movement of water through the body of the plant. Water comes in through the roots, up the stem and out of the leaves. The water travels through xylem cells and they are easily observed in our Ranunculus root section. Using high power, locate the red xylem cells in the very center of the root cross section. Draw five of the largest xylem cells Make sure you can distinguish these cells from the cortex cells you drew previously. Measure the diameters of the five xylem cells using the micrometer scale and record their sizes: 1) 2) 3) 4) 5) How are the xylem cells different from the cortex cells you drew earlier? Section 9 - Characteristics of Life - Responsiveness Responsiveness is the ability of living things to respond to stimuli. 1. Obtain the clean glass slide and the small square coverslip from the blue box in your booth. If you are missing either of these pieces, there are extras available at the instructor s desk. If your slide just needs cleaning, rinse it at the lab sink and dry it with the Kimwipes at your booth. 2. Take the slide and coverslip to the pond water beaker. DO NOT STIR the water you will find the most organisms in the brown material at the bottom of the beaker. 1.13

14 3. Place just ONE DROP of pond water (with the brown material) in the central part of the slide and cover gently with the cover slip, as shown: Start with scanning and look around for moving creatures. You will see lots of things that aren t moving, but we want to study the movements of living things. If you see perfectly round circles with dark borders, these are air bubbles ignore those. You may need to adjust your light to see the more delicate creatures. Many of the creatures are fast and small. It s best to keep looking for something big and slow enough you can observe long enough to complete the drawing below. Make a detailed sketch of your favorite pond creature. What sort of stimuli are your organisms responding to? (Example bumping into objects or other organisms): Rinse off your slide and coverslip gently at the sink, and put them both back into your blue box. Sometimes the coverslips break as you clean them and that s okay! Just get another one at the instructor s desk if it does break. 1.14

15 Section 10 - Characteristics of Life - Reproduction Reproduction is the production of new individuals of a species. Record the definitions of the two types of reproduction: Type of Reproduction Definition Example Asexual Budding Sexual Egg and sperm The alternate term for sex cells (eggs and sperm) is. 1.15

16 Section 11 - Characteristics of Life - Adaptation Define adaptation: The program will describe several different types of adaptations. Record the examples when they are summarized for you. Type of Adaptation Definition List three examples for each Physical Physiological Behavioral When you have finished the lab, make sure your microscope is turned off and you return the program to the Main Menu. (Do NOT shut down the program!) 1.16 See you next week!

17 Self Test At the end of each lab we provide you with some sample test questions. You can complete the self test at home and check your answers in Appendix 3 at the back of this lab manual. 1. A graph which shows the number of birds in each of seven weight categories would be an example of a/an: a. indirect observation b. point graph c. micrometer d. characteristic of life e. histogram 2. Which part of the microscope contains the micrometer scale: a. mechanical stage b. ocular c. coarse focus d. iris diaphragm e. high power objective 3. Which of these statements is true of xylem cells: a. they contain starch b. they allow water movement in a plant c. they are a critical cell involved in reproduction d. they are usually over 5 cm in length e. they are a type of pond organism 4. An object which is 5 mm long is equal to: a cm b. 50 cm c. 0.5 cm d cm e. none of these 5. What is the mean in this set of data: (insert normal distribution) a. 6.0 m to 26 m b. 16 m c. 400 m d. 250 m e. 300 m 1.17

18 6. When you exercise vigorously, you begin to sweat to cool your body. This physiological reaction maintains your body temperature. This is an example of: a. homeostasis b. adaptation c. metabolism d. organization e. reproduction 7. What is the size of this object on scanning power: a µm b. 25 µm c. 5 µm d. 125 µm e. 0.5 µm 8. Which objective lens do you always place into position first when viewing microscope slides: a. ocular b. scanning c. high power d. low power e. coarse 9. In plants, the function of the cortex cells is to: a. move water throughout the plant b. store sugar in the form of starch grains c. respond to light d. absorb light e. store fat 10. Many animals grow a thicker coat of fur in the winter to stay warm. This is an example of which type(s) of adaptation: a. behavioral b. physiological c. physical d. seasonal e. both b and c 1.18

19 Lab 2 Introduction to Chemistry Section 1 - Atomic Structure Section 2 - Energy Shell Diagrams Section 3 - Molecules Section 4 - Chemical Bonds - Covalent Bonds Section 5 - Chemical Bonds - Ionic Bonds Section 6 - Chemical Bonds - Hydrogen Bonds Section 7 - Chemical Reactions Section 8 - ph, Acids and Bases Section 9 - Effect of ph on Enzyme Activity Name Biology 3 ID Number Objectives Upon completion of this laboratory exercise, you should be able to: 1. Recognize the definitions and examples of the following: atom, element, atomic number, molecule, compound, chemical bond, chemical reaction and enzyme. 2. Identify the six major elements that make up living organisms. 3. Identify the parts of an atomic structure - nucleus, energy shell, neutrons, protons and electrons. 4. Identify the atomic structures of hydrogen, nitrogen, oxygen and carbon. 5. Interpret chemical and structural formulas. 6. Identify the structural formulas and molecular models of O 2, H 2 0, CO 2, NH 3, CH 4 and NH 2 CH 2 COOH. 7. Identify the parts of chemical reactions (reactants, products, enzyme) and their roles in a reaction. 8. Define the types of chemical bonds (covalent, ionic and hydrogen). Be able to discuss the role of electrons in each type and know the relative strength of each. 9. Understand the ph scale, know the definitions and examples of neutral, acid, base, hydrogen ion and hydroxide ion. 10. Define the terms hypothesis, control and variable in relation to experimental methods. 11. Describe the effect of ph on tyrosinase activity. 2.1

20 Section 1 - Atomic Structure Define atom: Define element: List the six major elements that make up 99% of the elements in all living tissue: What is the helpful acronym to remember this list of elements? The table below lists some common elements. Fill in the full name of these elements and place an asterisk (*) next to the major elements that are found in living organisms. Chemical Symbol Element name # Protons Chemical Symbol Element name # Protons H Na Li P C S N Cl O K F Ca Complete the following table by indicating the locations and electrical charges, if any, of the subatomic particles. Subatomic Particle Location in the Atom Electrical Charge Electron Proton Neutron Return to the program 2.2

21 Section 2 - Energy Shell Diagrams Define atomic number: We can use energy shell diagrams to depict a very simple, two-dimensional model of an atom. Hydrogen atom first energy shell with 1 electron nucleus with 1 proton (this type of hydrogen does not have a neutron) Nitrogen atom first energy shell with 2 electrons second energy shell with 5 electrons nucleus with 7 protons and 7 neutrons Energy shells First Capacity 2 electrons Second 8 electrons Third 18 electrons (reaches a stable point at 8) You should memorize these capacities before you continue the lab! 2.3

22 Fill in the energy shell for each of the elements listed below, using the capacity rules. Section 3 - Molecules Define molecule: There are two easily recognized types of molecules, depending on how many elements are present. Fill in the definitions: Define diatomic molecule: Define compound: A chemical formula shows the number of atoms of each type of element. When the symbol for a chemical element is not followed by a subscript, what does this mean? 2.4

23 This table shows some of the most common biological molecules that you should memorize. Name Chemical Formula Type of Molecule List the elements contained in the molecule Oxygen O 2 Water H 2 O Carbon dioxide CO 2 Methane CH 4 Glucose C 6 H 12 O 6 When you see a large number in front of a chemical formula (such as 3 H 2 O), what does that indicate? Here is the chemical formula for the amino acid called glycine: NH 2 CH 2 COOH What is the total number of atoms of nitrogen? Carbon? Hydrogen? Oxygen? Notice that the chemical symbol for hydrogen appears in three different places in the formula. This way of writing the chemical formula is very helpful in determining how the molecule is arranged, in other words, its structural formula. Here is the structural formula for glycine: What is the total number of atoms in the molecule? Section 4 - Chemical Bonds - Covalent Bonds Define chemical bond: Review the three subatomic particles you used in your energy shell diagrams. Which one of these subatomic particles participates in a chemical bond? 2.5

24 The element sulfur (S) has an atomic number of 16. How many protons does it have? How many electrons would it have? How many energy shells would it have? All atoms attempt to reach a stable electronic configuration. Review the energy shell capacities and fill in their stability points: The first shell is stable with electrons the second shell is stable with electrons the third reaches a stable point with electrons. Define covalent bond: What is the term used to describe an atom with a filled outside shell? Return to the program. Fill in the table with the three different versions of methane: Chemical Formula of Methane Energy Shell Diagram of Methane (fill in the missing electrons) Structural Formula of Methane Notice that with this configuration of carbon with four hydrogens, all outside energy shells are filled, at least part of the time. This results in extremely stable and strong covalent bonds. 2.6

25 Examine these structural formulas: Ammonia Water Glycine Because of the number of electrons in the outside energy shell of each element, there are a limited number of bonds possible. Hydrogen can only form one covalent bond. How many bonds can carbon form? Nitrogen? Oxygen? (Hint look at the structural formulas above) Notice that certain elements, carbon and oxygen especially, sometimes form double covalent bonds. At your booth, you will find a box of molecular model pieces. Take a look at the various pieces before beginning - small colored atom centers and two lengths of white flexible covalent bonds. Atom Center Color Covalent Bond Used between the following elements: Hydrogen white Short Bonds Hydrogen bonded to oxygen, nitrogen or Oxygen red carbon Nitrogen Carbon blue black Long Bonds Any other combination of elements not involving hydrogen (for example carbon to carbon, carbon to nitrogen, nitrogen to oxygen, etc.) Note the conditions for using each type of bond. Hydrogen atoms are very small, so we must use the short bond to indicate its relative position to the larger atoms such as carbon, nitrogen and oxygen. Also note how flexible the long bonds are, because you may have to bend around two bonds to join a carbon with oxygen in the double covalent bonds. 2.7

26 Construct the following molecules with the pieces in your kit. Keep the models assembled until you ve had the glycine checked by the instructor. Section 5 - Chemical Bonds - Ionic Bonds Define ionic bonding: Define ion: Notice that ions can be either negatively charged (by gaining an electron) or positively charged (by losing an electron). If we have two oppositely charged ions, they will be held together. In the space below, show how the ionic bond forms between atoms of sodium (Na) and chlorine (Cl). The correct number of energy shells is shown in the beginning diagram for you. Draw the correct number of energy shells and electrons for the end state. Beginning state (atoms) End state (ions) Make sure you have indicated the correct charge (+ or -) of each of the ions in the end state. 2.8

27 Section 6 - Chemical Bonds - Hydrogen Bonds Define hydrogen bonding: Now that you have actually built a water molecule, you know that the two hydrogen atoms end up essentially on one side of the molecule and the oxygen atom on the other, resulting in a polar molecule. Indicate the partial charges on this molecule. Draw four water molecules (4 H 2 O) to show the proper orientation of each molecule. Section 7 - Chemical Reactions The chemical reaction shown below depicts the decomposition of two molecules of hydrogen peroxide (2 H ), using an enzyme. catalase 2 H 2 O 2 2 H 2 O + O 2 Identify the components: Enzymes reduce the amount of energy required to complete the reaction and are therefore able to increase the speed of a reaction. Almost every reaction happening in your body is using an enzyme. 2.9

28 The following experiment will demonstrate the action of an enzyme called tyrosinase. Here is the chemical reaction you should memorize (the names only, you won t have to learn the chemical formulas for these). Tyrosinase 2 C 6 H 6 O 2 + O 2 2 C 6 H 4 O H 2 O pyrocatechol oxygen quinone water 1. Obtain three test tubes from the counter next to the sink and place them in a wooden test tube holder. 2. Fill each tube halfway with D.I. water from the large plastic container. This water will provide a medium for the reaction and does not participate directly in the reaction. D.I. means it has been de-ionized to prevent any impurities from interfering with the reaction we re interested in. 3. Add 10 drops of pyrocatechol to tubes A and C. (Squeeze the bottles gently for one drop at a time) 4. Add 20 drops of tyrosinase to tube B and C. 5. Gently mix the contents of each tube with the proper glass rod. Fill in the second and third columns of the table below. Tube Contents Initial color (immediately after adding chemicals) A Color after 5 minutes B C 6. Take your tubes to your booth and wait five minutes. After five minutes, examine the tubes for any color change. Look down through the tubes to look for color change. Using a white background will help determine the level of color change. Fill in the last column in the table above with your results. (If you detect another color such as pink, brown or purple in your test tube, this is NOT the reaction we are looking for. Ignore these colors.) What compound from the chemical reaction above is yellow? (Circle this compound in the chemical reaction shown at the top of the page) What is the function of the enzyme in this reaction? What is the name of the enzyme? 2.10

29 This basic experiment demonstrates the importance of controls in science. We have now confirmed that two substances must be present to cause the reaction. You have probably never used the chemical pyrocatechol before, but now you know it will remain colorless until acted upon by a specific enzyme. 7. Rinse out your test tubes and leave them upside down in the large test tube rack to drain. Section 8 - ph, Acids and Bases Before we begin the last experiment, we will examine a fundamental chemical quality of liquids - their ph level. Knowing the ph of a solution is critical to understanding the physiology of a living organism. The ph scale shows the relative acidity or alkalinity of a solution: Solutions with a ph of 7 or less are acidic (the lower the ph value, the greater the acidity). Solutions with a ph greater than 7 are basic, or alkaline (the higher the ph value, the greater the alkalinity). Define neutral: Define acid: Write the symbol for a hydrogen ion: If the compound HCl is an acid, how would it dissociate? HCl + Define base: Write the symbol for a hydroxide ion: If NaOH is a base, how would it dissociate? NaOH

30 Now you will measure the ph of some common household substances. Before you do the actual measurement however, please make a hypothesis about each substance on the table below. A hypothesis is your prediction or guess about the outcome of an experiment. Household substance Cola Lemon juice Dish soap ph balanced shampoo Hypothesis (Will the solution be acid or basic? You could indicate a ph value if you wish) ph value (after testing) Testing ph 1. Go to the demonstration table area and find the beaker with the phydrion paper. This is a commercially available product which has been treated with a wide range of chemicals that will turn different colors depending on the ph of the solution. 2. Pick up just one piece of phydrion paper with the forceps (scientific style tweezers). 3. Dip the paper into the cola solution. Compare the color of the wet phydrion paper to the ph color scale located on the table. Note: if the paper stays the original orange color, this is still a valid color on the color scale and indicates the ph of the solution. 4. Record the numerical ph value on the last column of the table above. 5. Repeat for each solution. Use a fresh piece of phydrion paper for each solution. Section 9 - Effect of ph on Enzyme Activity Now we will put together several chemical concepts with our last experiment. Before we begin the experiment, let s review the results of your first experiment with pyrocatechol. Tyrosinase 2 C 6 H 6 O 2 + O 2 2 C 6 H 4 O H 2 O pyrocatechol oxygen quinone water 2.12

31 What two substances had to be together in the tube for the formation of quinone? and What color is quinone? In that first experiment, what do you think the ph of the solution was (hint - what is the ph of D.I. water?) How do you test the ph of a solution? Now we will do an experiment to see if the ph of the solution in which the reaction is taking place will affect the results. At the demonstration table are three large plastic containers of clear solutions. Although all three look alike, they are in fact different in ph value and so ph will be our experimental variable (an experimental condition that we are testing). 1. Obtain three dry test tubes and place them in the wooden test tube holder. Be very careful not to mix up the three tubes as you complete the experiment - you may label each tube with the wax pencil provided if you wish. 2. Take the tubes to the demonstration table and fill them halfway with the three ph solutions, solution A in test tube A, solution B in test tube B, and solution C in test tube C. Your variable is now ready. 3. Test the ph of each solution using the phydrion paper and record the ph value of each test tube on the table on the next page. 4. Add 20 drops of tyrosinase and 10 drops of pyrocatechol to all three tubes and stir the contents gently with the appropriate glass rod. Make a hypothesis about the possible result - will quinone be produced in all three tubes? 5. After five minutes examine each tube carefully for a color change (remember to look down through each tube over white paper and ignore any color other than yellow). Note: You must show the instructor your test tubes when you get your graph checked! 2.13

32 6. Record your results by comparing your test tubes to the standards (results from previous experiments which have been assigned values) on display. The amount of quinone produced in each tube is directly related to the activity of the enzyme. Tube ph Enzyme Activity (0, +, ++ or +++) A B C 0 = no reaction, + = slight reaction, ++ = moderate reaction, +++ = strong reaction 7. Graph your results. (Before you begin, determine whether this type of data should be represented by a point graph or a histogram.) Enzyme Activity ph Bring your test tubes and this graph up to the lab instructor for checking: What is the name of the enzyme you used today? At what ph does this enzyme work best? Is the enzyme able to react in all three ph solutions you tested? Would you expect other enzymes to have specific ph requirements? Once your graph and test results have been checked by the instructor, rinse out your test tubes and place them upside down in the large test tube rack next to the sink. 2.14

33 Self Test 1. Which of these subatomic particles are found in the atomic nucleus: a. electrons and elements b. atoms and molecules c. protons and neutrons d. hydrogen and oxygen e. energy shells and polar particles 2. Which of the following lists the six major elements that make up living things: a. carbon, nitrogen, water, salt, protein and fat b. water, bases, acids, hydrogen ions, hydroxide ions and chloride ions c. nitrogen, carbon, phosphorous, hydrogen, oxygen and sulfur d. oxygen, carbon, sodium, chlorine, hydrogen and water e. carbon dioxide, water, glucose, calcium, salt and nitrogen 3. The element neon has 10 protons. How many energy shells would it have: a. 2 b. 10 c. 1 d. 20 e A molecule of acetoacetic acid has the formula CH 3 COCH 2 COOH. How many H atoms are in this molecule: a. none b. three c. six d. thirteen e. five 5. How many covalent bonds can an atom of carbon form: a. none carbon can only form ionic bonds b. two c. five d. six e. four 2.15

34 6. What type of bonds are found in sodium chloride (table salt): a. hydrogen b. nuclear c. covalent d. electron e. ionic 7. Which of these statements is true of glycine: a. there are four elements and ten molecules b. there are ten elements and four atoms c. there are four atoms and ten covalent bonds d. there are five hydrogen bonds and ten atoms e. there are four elements and ten atoms 8. Which of these is true of water: a. it can form hydrogen bonds b. it has two covalent bonds c. it is a polar molecule d. it is a compound e. all of these are true of water 9. Which of these is true of the tyrosinase reaction: a. tyrosinase turns yellow in a neutral solution b. tyrosinase speeds up the reaction of pyrocatechol and oxygen c. tyrosinase works well under acidic conditions d. tyrosinase is a reactant e. tyrosinase is an element 10. When you were setting up a test tube with just water and pyrocatechol (no tyrosinase), you were confirming that pyrocatechol does not turn yellow by itself. This is called a: a. variable b. standard c. polar sample d. control e. hypothesis 2.16