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Unit 4 Activity Workbook

Unit 4 Activity Workbook - Unit Four Activity Cellular...

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Unformatted text preview: Unit Four Activity Cellular Metabolism ACTIVITY #4 Name: ________________________________________ All cells must process energy into usable forms and deal with the byproducts of the processing. Protein, lipids, and carbohydrates are consumed by organisms and the energy they contain is converted into ATP, the energy currency of the cell. This is a complex process involving a number of enzyme‐mediated reactions; however, we can summarize the process in terms of input and output products with a very simple equation: C6H12O6 + 6O2 → 6CO2 + 6H2O + energy Cellular respiration uses a chemical reaction called a redox reaction, short for reduction/oxidation. The basic concept of redox is the transfer of electrons. To help you remember which reaction loses an electron and which gains an electron, use this mnemonic: Leo goes Ger Lose electrons oxidation – gain electrons reduction The catabolic pathway of cellular respiration oxidizes organic fuels thus extracting the energy in the fuel to make ATP. There are three processes involved in respiration; glycolysis, the citric acid cycle, and oxidative phosphorylation. Only glycolysis is common to all living organisms, the citric acid cycle and oxidative phosphorylation only occurs in organisms that use oxygen. Oxygen, as you recall, is highly electronegative and “pulls” the electrons down the ETC, electron transport chain in aerobic respiration. As with any chemical reaction, we can measure the reaction in two basic ways; by measuring the amount of reactants before and after the reaction, or by measuring the amount of product. In the Unit Two Activity we measured the amount of H2O2 before and after the reaction to determine the amount of reactant catabolized. That reaction was 2KMnO4 + 3H2SO4 + 5H2O2 → 2MnSO4 + K2SO4 + 8H2O + 5O2. Unit Four Activity Cellular Metabolism Page 1 Goals: o o o o o o o o o Measure the consumption of oxygen by respiring seeds Compare respiration rates at two different temperatures Determine an experimental variable Use chromatography to separate plant pigments Calculate Rf values from collected data Study photosynthesis with isolated chloroplasts Understand the process of cellular respiration Understand the process of photosynthesis Understand anaerobic pathways Metabolism PowerPoint Project: Metabolism is the set of chemical reactions that happen in living organisms to maintain life. The ATP cycle consists of catabolism of ATP to extract energy for cellular processes and Anabolism in cellular respiration to construct ATP from ADP. The chemical reactions of metabolism are organized into metabolic pathways, in which one chemical is transformed through a series of steps into another chemical, by a sequence of enzymes. The metabolism of an organism determines which substances it will find nutritious and which it will find poisonous. For example, some prokaryotes use hydrogen sulfide as a nutrient, yet this gas is poisonous to animals. The speed of metabolism, the metabolic rate, also influences how much food an organism will require. Each student will be assigned one of the following metabolic pathways to create a PowerPoint presentation and present it to the class. The PowerPoint topics are: Glycolysis Citric acid cycle Oxidative phosphorylation/electron transport and chemiosmosis Photosynthesis And fermentation with an overview of respiration This will not be an ordinary PowerPoint presentation; in fact, if you would prefer to assemble another type of presentation it is permissible. The object is to create a presentation that will substitute symbols and diagrams that you choose for the molecules and elements of the metabolic pathway you have been assigned. For example, the process of phosphorylating a G‐Protein could be shown: Unit Four Activity Cellular Metabolism Page 2 Rubric: Illustrations: (55 points) Clearly illustrate all molecules, enzymes, and substrates Clearly illustrate the compounds that enter the process Clearly illustrate the compounds that exit the process Clearly illustrate the metabolic pathway Presentation: (55 points) Knowledgably describe the process Explain where the compounds that enter the process comes from Explain where the compounds that leave the process go Laboratory 4 – A: Germinating the Peas and Building the Respirometers: = unphosphorylated G-Protein = phosphorylated G-Protein = ADP = ATP You will begin by preparing the lab by germinating pea seeds that will be used as the living organism we will measure the respiration of. Then you will set up the equipment necessary for the lab and consider the rates of respiration of pea seeds under various environmental conditions. Germination is the process in which a plant or fungus emerges from a seed or spore and begins growth. The most common example of germination is the sprouting of a seedling from a seed of an angiosperm or gymnosperm. However the growth of a sporeling from a spore, for example the growth of hyphae from fungal spores, is also germination. In a more general sense, germination can imply anything expanding into greater being from a small existence or germ. We will use six respirometers to measure the amount of respiration under two environmental conditions and to provide a control for our experiment. We will time the respiration process to determine the rate of respiration for the two environmental conditions. Unit Four Activity Cellular Metabolism Page 3 Materials: • • • • • Peas Plastic cups Plastic bag Metal washers Adhesive • • • • • Flat‐bottomed glass vials Scissors Parafilm® Rubber stoppers Glass pipets Cautions: • You will be using glass pipets for the experiment and there is a risk of breaking the pipet. Use caution when inserting your pipet into the rubber stopper. Procedure: Germinate the peas Place the peas that are to be germinated into a cup or beaker. Cover them with spring water to a depth at least three times their height in the container. This compensates for the expansion of the peas as they swell Allow the peas to soak overnight Build the Respirometers Glue a metal washer to the bottom of each of the 9 flat‐bottomed glass vials (see Illustration 1a). Cut the Parafilm® into 2” × 1” strips. You will need one 2” × 1” strip of Parafilm® for each respirometer, and each student group needs nine respirometers. For each respirometer top, gather one rubber stopper, one 1‐mL glass pipet, and one strip of Parafilm®. To assemble each top, wrap a strip of Parafilm® tightly around a glass pipet, approximately 1–1 ½ inches from the blunt end of the pipet (see Illustration 1b). Next, hold the pipet at the Parafilm® and carefully insert the blunt end of the pipet through the hole in the rubber stopper until an airtight seal is formed. o Hold the pipet close to the stopper and push carefully.. The final assembly should resemble Illustration 1c. Unit Four Activity Cellular Metabolism Page 4 Second Day of Germination Once you have let your peas soak overnight, pour off any remaining water and place the peas on wet paper towels. Completely cover the peas with wet paper towels and place them in a plastic bag. Close the bag and store it in a warm, dark place over a second night Third Day of Germination Examine the peas. At least some of them should possess ruptured seed coats from extension of the hypocotyl. If not, return the peas to the bag for a third night before using. Laboratory 4 – B: – Measuring Respiration: In this portion of the lab we will use the seeds and respirometer we constructed to compare the respiration rates of seeds at room temperature to the respiration rates of seeds that are below room temperature. You will also come up with another experimental variable to test. Materials: • • • • • • • • • • • • Styrofoam cups Respirometers Room‐temperature water Cold water Container of ice Germinating peas Nongerminating peas Glass beads Respirometers Graduated cylinder Absorbent cotton balls Nonabsorbent cotton • • • • • • • • • 15% potassium hydroxide (KOH) solution Dropping pipets Forceps Thermometers Food coloring Stopwatch or timer or clock with second hand Calculators (optional) Computer Material needed for student variable Cautions: • • Be cautious of broken glass with the pipets KOH is caustic, avoid skin contact and handle and dispose of properly Unit Four Activity Cellular Metabolism Page 5 Procedure: Prepare three water baths (cups of water) deep enough to completely submerge your respirometer. This is to buffer the respirometers against temperature change and to provide two temperatures, and a third variable for testing: room temperature, a colder temperature (approximately 10°C), and a student selected variable. Place a thermometer in each cup. If necessary, add ice to the cold‐temperature tray to further cool the water to get it as close to 10°C as possible. While waiting for the cold‐water temperature to stabilize at 10°C, prepare three respirometers to test at room temperature, an identical set of three respirometers to test at the colder temperature, and another set of three respirometers to test the student selected variable Assemble your respirometer by place an absorbent cotton ball in the bottom of each respirometer vial. Use a dropping pipet to saturate the cotton with 2 mL of 15% KOH o Be certain that the respirometer vials are dry on the inside. Do not get KOH on the sides of the respirometer.) Place a small wad of dry, nonabsorbent cotton on top of the KOH‐soaked absorbent cotton. The nonabsorbent cotton will prevent the KOH solution from contacting the peas. It is important that the amounts of cotton and KOH solution be the same for each respirometer. You will need a set of peas and/or beads for testing each variable. o Respirometer 1: Put 25 mL of H2O in your 50‐mL graduated cylinder. Drop in 25 germinating peas. Determine the volume of water that is displaced (equivalent to the volume of peas). Record the volume of the 25 germinating peas. Remove these peas and place them on a paper towel. o Respirometer 2: Refill the graduated cylinder to 25 mL with H2O. Drop 25 dry, nongerminating peas into the graduated cylinder. Next, add enough glass beads to equal the volume of the germinating peas. Remove the nongerminating peas and beads and place them on a paper towel. o Respirometer 3: Refill the graduated cylinder to 25 mL with of H2O. Add enough glass beads to equal the volume of the germinating peas. Remove these beads and place them on a paper towel. Place 25 germinating peas in your respirometer vial(s) 1. Place 25 dry peas and beads in your respirometer vial(s) 2. Place beads only in your respirometer vial(s) 3. Unit Four Activity Cellular Metabolism Page 6 Insert a stopper fitted with a calibrated pipet into each respirometer vial. The stopper must fit tightly. If the respirometers leak during the experiment, you will have to start over. Placement of Respirometers in Water Baths Place a set of respirometers (1, 2, and 3) in each water bath with their pipet tips emerging from the top. Make sure the entire vile is submerged Wait five minutes before proceeding. This is to allow time for the respirometers to reach thermal equilibrium with the water. If any of the respirometers begins to fill with water, you have a leak and must start over. After the equilibration period, use a small pipet and put one or two drops of food coloring in the tip of the respirometer. Position the respirometers so that you can read the scales on the pipets. Do not put anything else into the water bath or take anything out until all readings have been completed. Take Readings Allow the respirometers to equilibrate for another five minutes. Then, observe the initial volume reading on the scale to the nearest 0.01 mL. Record the data in the tables below for Time 0. Also, observe and record the temperature. Repeat your observations and record them every five minutes for 20 minutes. ROOM TEMPERATURE Unit Four Activity Cellular Metabolism Page 7 COLD TEMPERATURE STUDENT VARIABLE _____________________________________ 1. Transfer the data from the tables above to the AP Biology Unit 4 Activities Workbook – EXCEL program and save the program as instructed. Use the graphs to answer the following: Unit Four Activity Cellular Metabolism Page 8 2. The independent variable(s) is (are) ________________________________________. 3. The dependent variable is __________________________________________. 4. Write a hypothesis for each variable the experiment is designed to test. In this experiment, you measured the change in volume of the gas inside the respirometers. The general gas law describes the state of a gas under given condition: pV = nRT • Where: o p = pressure of the gas o V = volume of the gas o n = kmoles (number of molecules) of gas o R = universal gas constant [8314 joules/(kmole)(K)] o T = temperature of the gas in K The general gas law restated to solve for volume: Unit Four Activity Cellular Metabolism Page 9 5. Using the general gas law and your experience in this lab, give the variables that had to be controlled for your data to be valid. State the controls used for each variable and any means used to correct for the influence of a variable(s). 6. Which of the respirometers (1, 2, or 3) serves as a negative control? Explain your answer. 7. In reference to the general gas law, and assuming your control measures worked, a change to which of the variables led to the observed change in volume (Corrected ∆V in the tables)? Explain your answer. Unit Four Activity Cellular Metabolism Page 10 8. Using your graph and data tables, summarize your findings, comparing results from respirometers 1 and 2, and results obtained at room temperature vs. results at the colder temperature and the results from your selected variable. Speculate as to the cause(s) of any differences between the treatments. 9. From your graph, calculate the rate of oxygen consumption for each treatment: a. germinating seeds at room temperature = ____________ mL/min b. germinating seeds at colder temperature = ____________ mL/min c. germinating seeds at student variable = _____________mL/min d. dry seeds at room temperature = ____________ mL/min e. dry seeds at colder temperature = ____________ mL/min f. dry seeds at student variable = _____________mL/min Unit Four Activity Cellular Metabolism Page 11 Laboratory 4 – C: – Leaf Pigment Chromatography: In science, it is often useful to know if a material is composed of a pure substance or if it is a mixture. This requires the selection of a method to separate the components of a possible mixture. Paper chromatography is a technique that is widely used to separate mixtures of biological compounds. In this activity, you will use paper chromatography to determine if a green leaf contains only one pigment or a mixture of pigments. You will do this by placing a line of leaf pigment near one edge of a sheet of chromatography paper. You will place this edge of the paper into a solvent. The solvent is itself a mixture of acetone and petroleum ether. The solvent will be absorbed into the paper and encounter the line of pigment. If the pigment is a mixture of molecules, it is likely that some molecules will be more soluble in the acetone and others in the petroleum ether. Different molecules may attach more‐or‐less strongly to the cellulose of the paper through the formation of hydrogen bonds. If the leaf pigment is a mixture, you can expect that as the solvent travels up the chromatography paper, different molecules will dissolve in the solvent and travel up the paper at different rates. This will lead to the formation of different color bands on the paper, one band for each substance in the mixture. If the leaf pigment is not a mixture, you can expect to obtain only one color band. Four pigments are widely found in leaves: carotene, xanthophyll, chlorophyll a, and chlorophyll b. Carotene is highly soluble in the solvent you are using. Its molecules do not form hydrogen bonds with cellulose. Carotene produces a faint yellow to yellow‐orange band. Xanthophyll is slightly less soluble than carotene in the solvent. It forms some hydrogen bonds with cellulose. Xanthophyll produces a yellow band. Both chlorophyll a and chlorophyll b readily form hydrogen bonds with cellulose. Chlorophyll a gives a bright green to blue‐green band. Chlorophyll b produces a yellow‐green to dark, olive green band. Materials: • • • Chromatography jar tightly capped with solvent Chromatography paper Green leaf • • • • Coin Small stapler or paper clips Ruler Fume hood Cautions: • • Both acetone and petroleum ether are highly volatile and flammable. Keep the chromatography jar tightly capped except when inserting or removing the chromatography paper. Avoid breathing fumes from the solvent, we will use the fume hood for safety Unit Four Activity Cellular Metabolism Page 12 Procedure: Your teacher will demonstrate the apparatus and techniques used in paper chromatography. Use the following steps as a guide. Before you begin the activity, familiarize yourself with the entire procedure. Obtain a piece of chromatography paper and one fresh spinach (or other) leaf. Make two pencil marks 1.5 cm from one edge of the chromatography paper, as shown in Figure 1. Lay the leaf on the chromatography paper, near one edge. Using the marks as a guide, lay a ruler on top of the leaf so that the edge of the ruler is on the paper exactly 1.5 cm from and parallel to the edge of the paper. Using the ruler as a guide, roll a coin over the leaf, driving the leaf pigments into the paper in a straight line 1.5 cm from the edge of the paper. You should see a dark green stripe of pigment. If not, repeat this step using the same 1.5‐cm line, but reposition the leaf so that you roll the coin over fresh leaf tissue. Use a pencil to mark the location of the bottom of the pigment line on the paper. Use this line as the origin. Place the chromatography paper in the jar so that the pigment streaked end of the paper is barely immersed in the solvent. The pigment stripe itself should not be in the solvent. Tightly cap the jar. Do not disturb the jar for several minutes, but continue to observe the chromatography paper within. When the solvent is about 1 cm from the top margin of the paper, remove the paper from the jar and immediately mark the location of the solvent front before it evaporates. Mark the bottom of each pigment band. Beginning at the origin line, measure the distance traveled by the solvent front and each of the pigment bands. Record the results in the table below. Number the bands so that Band 1 is the pigment band nearest the origin line at the bottom of the paper. Unit Four Activity Cellular Metabolism Page 13 For a given solvent and substrate system (in this case, cellulose), each pigment will move a distance that is proportional to the distance moved by the solvent. This is expressed as the Rf (Reference front) value, and it is a constant for the solvent/substrate/pigment. For example, suppose that a pigment moves 75 mm while the solvent moves 100 mm. Then: 10. Calculate Rf values for each of the pigment bands you have identified. Record this data in the table above. 11. Using the data you have collected, make at least tentative identifications of the chlorophyll band(s) and other major bands on your chromatography paper. Record these in the “Band Color/Identification” column of the table above. Unit Four Activity Cellular Metabolism Page 14 Laboratory 4 – D: – Light Reactions of Photosynthesis: In the light reactions of photosynthesis, light energy is absorbed by chlorophyll and used to excite electrons. The excited electrons then enter one of two electron transport chains. One chain converts ADP + P to ATP and the other converts NADP + H to NADPH. In this activity, you will add a solution of DPIP (2,6‐dichlorophenol‐indophenol, a blue dye) to a suspension of chloroplasts. The DPIP will substitute for NADP in the light reactions: DPIP + H → DPIPH. DPIPH is colorless, so as the light reactions take place, the blue color of the solution will diminish. You will use this color change as an indication that the light reactions are taking place and you will use the rate at which the color change takes place as a measure of the rate of the light reactions. We will use the USDA spectrophotometer to measure loss of color by DPIP. You will prepare a sample by adding chloroplast suspension, DPIP, and a buffer to water in a tube or vial called a cuvette. The cuvette is sized to fit into a test chamber of the instrument. The instrument works by shining a light of known intensity into one side of the cuvette. On the opposite side of the test chamber is a photocell. DPIP will absorb some of the light that enters the cuvette, thus, the photocell will “see” less light. As the light reactions take place, there will be less DPIP and the photocell will “see” more light. Since DPIP absorbs light most strongly at orange‐red wavelengths, you will set the spectrophotometer to read the amount of light transmitted in that part of the spectrum. Dr. Marshall at USDA may give you additional specific instructions for the spectrophotometer that you use. Materials • • • • • • • • • • Spectrophotometer 5 cuvettes Aluminum foil Heat sink (aquarium) Lamp 4 dropping pipets Vial of unboiled chloroplast suspension Vial of boiled chloroplast suspension Vial of 0.1 M phosphate buffer Vial of DPIP solution • • • • • • • • • • Distilled water Lens tissue Bucket of ice 4 squares of Parafilm® Labels Ruler Calculator Clock or timer Test tube rack (if needed for cuvettes) Computer Cautions • As with all laboratory procedures, use caution and proper laboratory protocol and listen to the laboratory director (Dr. Marshall) Unit Four Activity Cellular Metabolism Page 15 Procedures Refer to the table below for a summation of how you will set up the cuvettes. Important: Do not add the chloroplasts until you are instructed to do so in the numbered steps below. Handle cuvettes by their tops only. If you touch the sides, you will leave a fingerprint that may interfere with light transmission. Wipe the sides of a cuvette with lens tissue before inserting it into the test chamber. You have four dropping pipets for setting up the experiment. Keep track of them carefully and use them as directed, so that you do not cross‐contaminate reagents. The pipets have a 1‐mL graduation mark at the top of the neck, near the bulb. Turn on the spectrophotometer. Some models require a warm‐up period. Listen carefully to Dr. Marshall’s briefing on the operation of the USDA’s spectrophotometer. o You can set up your work area while the spectrophotometer is warming up. Once the spectrophotometer has warmed up, set it to read light transmission at 605 nm. Set up a work area as shown in the figure below. The water in the aquarium will absorb infrared radiation (heat) that could damage the chloroplasts. Unit Four Activity Cellular Metabolism Page 16 Label your cuvettes 1, 2, 3, 4, and 5 respectively. If your cuvettes have caps, label the caps also. If your cuvettes do not have caps, place the labels near the tops of the cuvettes. The labels must not block the light beam used by your instrument. Use a new, clean dropping pipet to add 4 mL of distilled H2O to Cuvette 1. Use the same pipet to add 3 mL of distilled H2O to cuvettes 2–5. Use the same pipet to add three additional drops of distilled H2O to Cuvette 5. Still using the same pipet, add 1 mL of phosphate buffer to each cuvette (1–5). Use a new, clean (second) pipet to add 1 mL of DPIP to cuvettes 2–5. Fashion an aluminum foil cover for Cuvette 2. The cover must prevent light from entering the cuvette. Obtain a vial of unboiled and a vial of boiled chloroplast suspension. Keep these vials on ice throughout this activity. Mix the unboiled chloroplast suspension by inverting the vial (make sure the cap is secure). Use a new, clean (third) pipet to add three drops of the unboiled chloroplast suspension to Cuvette 1. Calibrating the spectrophotometer o Set the spectrophotometer to zero by adjusting the amplifier control knob until the meter reads 0% transmittance. o Cap or cover Cuvette 1 with Parafilm® and gently mix the contents. o Insert Cuvette 1 into the test chamber and adjust the light‐control knob to get a 100% transmittance reading. o Make a mark on the label of Cuvette 1 so you can insert it in the same orientation each time you use it. (This will compensate for any variations in the glass walls of the cuvette.) Making readings with the spectrophotometer o When you add the chloroplasts to the dye solution, photosynthesis may decolorize the dye very quickly. Add chloroplasts to only one cuvette at a time and measure each cuvette’s transmittance immediately. o Mark each cuvette so you can insert it in the same orientation each time. o You will take % transmittance readings for each cuvette at 0, 5, 10, and 15 minutes. o Keeping the time for all five cuvettes can be tricky; before proceeding, determine how you will accomplish this. o You must mix the contents of each cuvette before placing it into the test chamber. Mix the contents by inverting the cuvette. Before you invert the cuvette, however, make sure that the cap is secure or that the Parafilm® forms a tight seal. o After each measurement, use Cuvette 1 to see if the spectrophotometer still reads 100% transmittance. o If not, readjust the spectrophotometer as needed. o Remember to mix the contents of Cuvette 1 before each use. Unit Four Activity Cellular Metabolism Page 17 Mix the unboiled chloroplast suspension and use the third pipet to add three drops of the suspension to Cuvette 2. Immediately mix the contents of Cuvette 2. Remove Cuvette 2 from its foil cover, insert it into the test chamber, and read its % transmittance. Record the results in the table below under “0 min.” Return Cuvette 2 to its foil cover, and place it in the test tube rack. Turn on the lamp. Repeat readings at 5, 10, and 15 minutes. Mix the contents of the cuvette each time before taking the reading. Mix the unboiled chloroplast suspension and use the third pipet to add three drops of the suspension to Cuvette 3. Immediately mix the contents of Cuvette 3. Insert it into the test chamber and read its % transmittance. Record the results in the table below under “0 min.” Place Cuvette 3 in the test tube rack. Repeat readings at 5, 10, and 15 minutes. Mix the contents of the cuvette each time before taking the reading. 12. When we return to the classroom, transfer the data from the table above to the AP Biology Unit 4 Activity Workbook – EXCEL program and use that to answer the following questions 13. What is the title the graph? 14. Identify the following: a. The independent variable is ___________________________________. b. The dependent variable is ___________________________________. 15. Write a hypothesis that this experiment is designed to test. Unit Four Activity Cellular Metabolism Page 18 16. What variables are tested in this experiment? Describe how each variable is tested and then describe the results of your experiment. 17. Why wasn’t DPIP added to Cuvette 1? 18. What was the purpose of adding three drops of chloroplast suspension to Cuvette 1? Unit Four Activity Cellular Metabolism Page 19 19. Why were three drops of water added to Cuvette 5? 20. What effect did boiling have on the chloroplast suspension? Testing Your Knowledge: 21. What is the first law of thermodynamics? 22. What is the second law of thermodynamics? 23. Explain how life can decrease entropy and not violate the second law of thermodynamics. Unit Four Activity Cellular Metabolism Page 20 24. What are the key properties (characteristics) of enzymes and what is their function in biological systems? 25. Define or describe each of the following: Unit Four Activity Cellular Metabolism Page 21 Use the graph below to answer the questions that follow: 26. What is happening at letter b? 27. What is the relationship between the energy of the reactants and the energy of the products? Unit Four Activity Cellular Metabolism Page 22 28. Define activation energy. 29. Which letter represents the activation energy for the reaction a. Without the enzyme? b. With the enzyme? 30. What does letter e represent? 31. What is the role of enzymes in biological systems? 32. What is the relationship between enzyme structure and enzyme specificity? Unit Four Activity Cellular Metabolism Page 23 33. Explain what happens in the induced‐fit model of enzyme action. 34. List 4 ways enzymes can lower activation energy. 35. How does substrate concentration affect the rate of an enzyme controlled reaction? Unit Four Activity Cellular Metabolism Page 24 Use the graph at the right to answer the questions that follow: 36. Why did the reaction rate for enzyme J drop when the temperature exceeded 50°C? 37. What is the optimal temperature for enzyme J? 38. How do you know this is the optimal temperature? 39. Could enzyme J be an enzyme found in the human body? Why or why not? Unit Four Activity Cellular Metabolism Page 25 Use the graph at the right to answer the questions that follow: 40. What is the optimal pH for: a. Enzyme K? ____________ b. Enzyme M? ____________ c. Enzyme L? ____________ 41. Which letter represents the activity of an enzyme that could be found in the stomach? 42. What happens to enzyme activity when the pH is higher or lower than the optimal pH? Why does this happen? Unit Four Activity Cellular Metabolism Page 26 43. Match the definition/description with the correct term. A Allosteric enzymes _______ Enzymes with two conformations – one active and one inactive B Coenzyme _______ Enzyme inhibitors that resemble the substrate and compete with the substrate for the active site C Cofactor _______ Chemicals that inhibit enzyme activity D Competitive inhibitors _______ Enzyme inhibitors that bind to the enzyme at a site other than the active site and cause the enzyme to change shape E Inhibitor _______ Organic cofactors; vitamins _______ Small, nonprotein molecules needed for enzyme reactions F Noncompetitive inhibitors 44. What is the role of each of the following in allosteric enzyme action? a. Inhibitor b. Activator Unit Four Activity Cellular Metabolism Page 27 Use the figure below to answer the questions that follow: 45. Which letter represents the enzyme? 46. If letter B represents the substrate, what kind of inhibitor (competitive or noncompetitive) does letter C represent? 47. How do you know? 48. What kind of inhibitor (competitive or noncompetitive) does letter D represent? 49. Describe what happens in feedback inhibition. 50. Describe what happens during cooperactivity. Activity 8 Page 28 51. Match each of the following occurrences to the correct part of the glucose metabolism process. If more than one answer is correct, write all letters in the blank. _________ Most of the ATP is made A. Glycolysis _________ Occurs only under anaerobic conditions B. Fermentation _________ Occurs only under aerobic conditions _________ Uses phosphorylation C. Cellular Respiration (aerobic) _________ Occurs under aerobic and anaerobic conditions D. Krebs Cycle _________ Can occur under anaerobic conditions E. Electron Transport Chain _________ Glucose splits into 2 Pyruvic acid molecules _________ Occurs in the mitochondria _________ PGAL forms _________ Lactic acid forms _________ Occurs in the cytoplasm _________ Produces CO2 and ATP _________ Ethanol produced _________ Acetyl‐CoA involved _________ Citric acid cycle _________ CO2 not a byproduct _________ H2O is a byproduct _________ Nets 2 ATP _________ Completes glucose metabolism Activity 8 Page 29 ...
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