Biol 150 Lab Exam 1 Review: Key Concepts & Guidelines

Montgomery College – Rockville Campus – BIOL 150 Lab Review Guide for Exam 1 Exercises 1-6 : Introduction to Science, Biomolecules, Microscopy, Osmosis, Respiration, Photosynthesis. Please note that questions in this document are a guide to prepare for Lab Exam 1. None of the questions are going to be copied and pasted on your exam by your instructor. Please print a copy and bring it with you to any of the review sessions you’re planning on attending. Use it even if you cannot make to any of the sessions offered this semester. M i croscop y (3) Watch these videos on how to use and clean a microscope: https://youtu.be/ROsc-IrJJ6M?rel=0 https://youtu.be/AHkWYFUaV9M?rel=0 Leica DM750 on YouTube: https://www.youtube.com/watch?v=YFtjnE6t9xY 1 A B C D E F G H I J K A B C D E F G H I J K

https://youtu.be/lo2aC_m2vyo L et te r Name Fu nc tio n A B C D E F G H I J K 1. Why do you think that the microscope is a very important instrument for studying biological specimens? Cells are microscopic, in order. Of a few micrometers. We can see fraction of a mm(1000x larger than the um). i. Cells are very small to see with our eyes (um size) 2. What changes do you expect to observe (size of the image, intensity of light, field of view, depth, resolution, etc.) as you go from lower to higher magnification? Size: increases Intensity of light: decreases Field of view: decreases Depth: decreases Resolution: Increases (ability to distinguish between two points) depth, increases resolution. 3. Compare the advantages and disadvantages of observing a specimen at total magnifications of 40X and 400X. at 40x: advantage is you can see a bigger part of your specimen; disadvantage is lower magnification and resolution. at 400x: advantage is higher magnification and resolution; disadvantage is that you see less of your specimen. Low Watch this video to review how to size under a microscope : https://edpuzzle.com/media/5ef274d8cb1f783f21e007fc 4. If the diameter of field of view of a light microscope at 40X magnification is 6000 micrometer (microns), what would be the field of view at 400X magnification? Magnif x diameter= constant-> M1.D1= M2.D2-> (40)(6000 um)= 400 D2-> (40)(6000 um)/400= > D2=600 um 2

5. Fill in the following: A) 3 mm = _ 3x1000=3000_ ___μm 3000__ C) __ 500/100=0.5 ____mm 0. = 500 μm B) ___ 4000/100=4_ __μm = 4000 nm D) 0.25 mm = __ 250 ____μm 6. The photograph on the right is a view of Elodea cells at 1,000x magnification using a compound light microscope that has field of view of 5,000 μm at 40x magnification. Use this to determine the length and width of these Elodea cells. Length= long dimension M1D1= M2D2=> 2 cell fit lengthwise in one diameter: one cell length= D2/2= 200 um/2-100 um 5 cells fit widthwise in one diameter: one cell width: D2/5= 200 um/5= 40 um D(1000)=(5000 um)(40) D= 200 um Length of 1 cell= 50% of diameter= 100 um Width of 1 cell= 1/5 of diameter ( 20%)= 40 um 3

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O rgan i c M o l ecu l es of L if e (2) 7. What are the four major classes of organic molecules produced by living organisms? Carbohydrates. Lipids, proteins, nucleic acids 8. What is a monosaccharide? Why are all monosaccharides and most disaccharides reducing sugars? Building blocks (monomers) of carbohydrates. They are reducing sugars because they have carbonyl group (C= O) 9. What is meant by the term reduction? What is a reducing agent? Reduction 1, Gain of electrons (RIG). A substance that donates electrons: becomes oxidized electrons to another substance. 10. What is meant by the term oxidation? What is an oxidizing agent? Oxidation is losing electrons. Oxidizing agent is a substance that takes electrons from another substance: becomes reduced agent takes electrons from another substance causing oxidation 11. Both Benedict’s and Barfoed’s solutions are made from the same ingredient. Why are their reaction capabilities different? Benedicts’s and Barfoed’s are copper ion solutions. Benedicts has an alkaline pH and Barfoed’s an acidic pH. Benedicts detcts reducing sugars but Barfoed’s only monosacchardies. 12. Suppose you have performed Benedict’s assay with glucose. Which molecule/ion has become oxidized? Which one has become reduced? Glucose is oxidized and Copper ions are reduced. Glucose reduced copper ions ( gives electrons to copper). zed. Cu2+ is reduced (Cu+) 13. In solution, chain and ring forms of glucose molecule exist in equilibrium. Explain this statement. The chain form is converted to the ring form and to the chain form constantly in a solution. In a given solution, some molecules will be in the chain form and some will be in the ring form. Only the chain form has the carbonyl group. open chain to the ring form. 14. Both fructose and glucose are reducing sugars. When these two simple sugars become chemically bonded, a disaccharide, sucrose, is formed. Why is sucrose not a reducing disaccharide? The reason is the way the rings of fructose and glucose are connected bury the carbonyl group in the glycosidic bond. It is impossible for any of the rings to open in a solution and reveal the carbonyl group. Without it, sucrose cannot be a reducing sugar. 4

he carbonyl of Sucrose is buried in the bond between glucose and fructose. 15. What are the monosaccharides and r educ i ng disaccharides that you assayed in lab? Glucose, fructose, galactose ( all monosaccharides ) and maltose and lactose are reducing disaccharides. 16. What is the difference between r educ i ng disaccharide and no n -r educ i n g disaccharides? Reducing disaccharides have the ability to open of the their rings in a solution and reveal the carbonyl group. Non-red disaccharides cannot any of their rings in solution and have no carbonyl group available . a. Reducing disaccharide has a carbonyl group which can reduce other substances 17. Write three names of polysaccharides and their function in cells. Starch ( plant-> energy store), glycogen ( animal-> energy store), cellulose ( 18. If you completely hydrolyze a starch molecule, what would you produce? You will get glucose. se In questions 19-23, select your answers from the list below a) sucrose b) maltose c) starch d) glucose e) egg albumin 19. This substance gives a negative Benedict's assay, a negative Barfoed's assay, a positive iodine assay and a negative Biuret assay. Answer Starch 20. This substance gives a positive Benedict's assay, a positive Barfoed's assay, a negative iodine assay, and a negative Biuret assay. Answer ___ Glucose _ ____ 21. This substance gives a positive Benedict's assay, a negative Barfoed's assay, a negative iodine assay, and a negative Biuret assay. Answer maltose/lactose b 22. This substance is positive in Biuret assay and negative in all other assays. a. Answer Egg albumin e 23. All the assays (Benedict's, Barfoed's, iodine, and Biuret) on this substance were negative. b. Answer Sucrose a 24. Benedict’s assay tests for all reducing sugars ( monoscchardies and some disaccharides) . 5

a. A positive reaction for Benedict’s assay produces orange/red ( solid) (green) color. b. Barfoed’s assay distinguishes between Monosacchardies( positive) and reducing disaccharides ( negative) . 25. A protein solution can be identified by performing the B biuret et assay. The solution turns violet or magenta color if the assay is positive. This color forms because of the presence of peptide bonds in proteins 6

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Scientific method (1) A group of scientists working for Company Y want to test a new chemical that they believe will act as a sunscreen and prevent sunburn. The same amount of lotion is applied to each person in the same size area and the test subject’s arm is exposed to direct sunlight. The amount of redness is measured every 5 min for a total of 30 min. For each person tested, 3 different lotions are applied to the test subject’s arm: I. a lotion with the new sunscreen chemical called SunX II. a lotion with a different active sunscreen chemical that the company currently sells successfully called Sun Kissed III. a lotion that has all the same ingredients as the sunscreens, except it has no active sunscreen chemical 26. What question is being asked in the experiment above? a. Is sunX an effective sunscreen? b. Is SunX a more effective sunscreen than Sunkissed? 27. What hypothesis is being tested in the experiment described above? Read entire description above carefully! SunX is a more effective sunscreen than SunKissed SunX will prevent redness more than Sunkissed 28. A hypothesis must be testable and falsifiable. Is the hypothesis you wrote above testable? Explain . Yes it is testable. We can measure redness which will tell us how effective the sunscreen is. 29. Is the hypothesis you wrote above falsifiable? Explain. Yes it is, because our results may show that the new sunscreen is not effective 30. What is the prediction based on this hypothesis? (Remember a prediction is written as an “If…, then….” statement.) If I apply SunX on people’s arm I will get less redness than if I apply SunKissed 31. What is the independent variable in this experiment? Why? The Independent Variable is the sunscreen 32. What is the dependent variable in this experiment? Why? Dependent variable: Amount of redness. 33. For this experiment, which group of patients is the experimental group (1, 2 or 3)? WHY? Group 1: we are testing this (linked to hypothesis) 34. Which group of patients is the negative control (I, II or III)? WHY? Group 3 (we do not expect an effect) 35. Which group of patients is the positive control (I, II or III)? WHY? Group 2 is the positive control: already known to be a sunscreen. 7

1 2 3 4 5 36. Based on the graph, is Sun X a more effective sunscreen than Sun Kissed? Explain how you came to your conclusion. It seems that SunX is more effective (assuming the data are significantly different) 37. Titles of graph and axes should allow the reader to quickly understand what information is in the graph. Write a “good” title for this graph. Effectiveness of SunX as a Sunscreen compared to Sunkissed Osmosis and diffusion (4) Study the set of five beakers shown here to answer questions 1 – 3: 38. Which beaker(s) contain(s) a solution that is hypertonic to the bag? a) Beaker 3 b) Beakers 2 and 4 c) Beakers 1, 2, and 5 d) Beaker 4 e) Beakers 3 and 4 39. Which bag would you predict to show the least change in mass at the end of the experiment? a. The bag in Beaker 1 b. The bag in Beaker 2 c. The bag in Beaker 3 d. The bag in Beaker 4 e. The bag in Beaker 5 40. Arrange the beakers in order of the mass of the bags inside them after the experiment has run for 30 minutes . List the bag that loses the most mass. a. 1, 2, 3, 4, 5 b. 1, 5, 2, 3, 4 c. 4, 3, 2, 5, 1 8 0 5 10 15 20 25 30 0 5 10 15 20 25 Lotion Alone Sun Kissed Sun X Time of exposure to sun (min) Amount of redness

d. 3, 2, 1, 4, 5 e. 2, 1, 5, 3, 4 41. A dialysis bag (permeable to water but not to sucrose) is filled with a sucrose solution and placed in a beaker containing 30% sucrose solution. The bag’s initial weight was 15 g, and after 15 minutes it weighed 17g. Calculate the percent change in weight of the dialysis bag. After 45 minutes, the same bag weighed 20g. What is the cumulative percent change in weight of the bag at that point? Percent change = [(17g-15g)15 g ]x100 = 13.3% Percent change = [(20g – 15 g)/15g]x 100 = 33.3 % 42. Assume that you have a 20 M glycerol stock solution. You need to make 5 different solutions for your experiment: 0 M or no glycerol, 2.5 M glycerol, 5 M glycerol, 7.5 M glycerol and 10 M glycerol. In each experiment you will need to make 50 ml of the diluted solution. Show your calculations for each solution: Final concentration of solution Amount of 20 M glycerol stock solution Amount of water Final volume of the solution 0 M glycerol 0 ml 50 ml 50 2.5 M glycerol 6.25 ml 43.75 ml 50 5 M glycerol 12.5 ml 37.5 ml 50 7.5 M glycerol 18.75 ml 31.25 ml 50 10 M glycerol 25 ml 25 ml 50 2 Table 1: The potato plugs were weighed (in grams) at 20 minute intervals and their mass recorded in the table below. 0 minutes 20 minutes 40 minutes 60 minutes 0.0M glucose 5.3 5.5 5.7 5.8 0.2M glucose 5.7 5.7 5.8 5.8 0.4M glucose 5.5 5.0 4.8 4.6 0.6M glucose 5.6 5.0 4.7 4.4 9

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Table 2: Calculate the percent change in mass for each time point and fill in Table 2. 0 minutes 20 minutes 40 minutes 60 minutes 0.0M glucose 0 [5.5- 5.3/5.30]x100= 3.77 [ 5.7-5.3/5.3]x 100= 7.55 9.43 0.2M glucose 0 0 1.75 1.75 0.4M glucose 0 -9.09 -12.7 -16.4 0.6M glucose 0 -10.7 -16.1 -21.4 43. Why do you have to calculate percent change in mass? You can compare potatoes of different sizes – percent change would be much more comparable than absolute mass. 44. Using the attached piece of graph paper, or excel, plot the percent change in mass of potato cores over time for each solution. Draw lines of best fit through each set of data (either manually, or on excel by adding the trendline). a) What is the dependent variable? ___ cumulative percent change in mass ___________ b) What is the independent variable? _____ time_ _______ c) Is the independent variable quantitative? ______ yes_ ________ d) Is the independent variable continuous? ____ yes_ ______ e) What kind of graph would be best to use? Circle one below. Bar Graph Line Graph f) Explain your choice of graph Use the TAILS checklist and graph all 4 lines on the following piece of graph paper.  Title  Axes  Intervals  Labels  Scale 10

Percent change in mass over time Time (min) 11

45. Next, calculate the rate of percent change for each glucose concentration by calculating the slope of each line on your graph. Include the units with your rate calculations. Fill out Table 4 NOTE: to calculate the slope of the line manually, take 2 points on each line of best fit and calculate the slope according to the formula below. If you are using excel, you can obtain the slope from the equation of the line of best fit (y = ax + b, where a = slope). Slope = Y 2 -Y1 = rate of percent change in mass X 2 -X 1 (min) Table 4:Rate of Percent Change in Mass Concentration Rate of Change (1/min) (slope) 0.0M glucose 0.14 0.2M glucose 0.044 0.4M glucose -0.18 0.6M glucose -0.27 Using the graph paper attached, plot the rate of change (1/min) versus glucose concentration (M) . Draw the line of best fit through your points. a) What is the dependent variable? _______ Rate of change in mass (g/min) ____________________ b) What is the independent variable? _______ concentration ____________________ c) Is the independent variable quantitative? _____yes_____________ d) Is the independent variable continuous? _______yes___________ e) What kind of graph would be best to use? Circle one below. Bar Graph Line Graph f) Explain your choice of graph Both variables quantitative The isotonic concertation is the x-intercept: rate of change is zero, there is no change in mass. That Is the conertaion that is equal to the bag of concertation. 12

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Use the TAILS checklist and graph all 3 lines on the following piece of graph paper.  Title  Axes  Intervals  Labels  Scale X:Rate if change in mass Effects of glucose concertation on rate of change in mass 13

Y:Glucose ( M) 46. What can you tell from this graph that you couldn’t tell from the previous graph? You can determine the isotonic concertation by finding the x intercept ( rate of change is zero on the concertation ) Cellular respiration (5) Here is a video on how this lab is set up and run: https://youtu.be/BMblymbYsf0 Here is a video on endotherms and ectotherms: https://www.youtube.com/watch?v=TSUCdLkI474 Here is a video on how to analyze data for this lab: https://youtu.be/XHsPLBOO_lY 47. What is aerobic respiration? Where does it take place? How many ATPs are produced by aerobic respiration? Glycolysis, Kerns cycle, Oxidative Phosphorylation, cytosol and Mitochondria. 36 ATP With O2 – part of it in the cytosol and part in the mitochondria. Over 30 ATPs produced. 48. What is fermentation? Where does it take place? What is the advantage of fermentation? What is the disadvantage of it? What is the difference between complete cellular respiration and fermentation? Anaerobic process: glycolysis+ 1-2 steps to oxidize the electron carriers. In the cytoplasm. Advantage: energy produced without oxygen. Disadvantage is that only 2 ATP is produced (compared to 36 of aerobic process). Aerobic process vs anaerobic. Long proves vs short process. Much more energy vs little energy. An anaerobic version of respiration. Happens in the cytosol. Organisms can survive without O2. It is not as energy efficient. 49. Complete the summary equation for cellular respiration: ____C6H22O6_______ + ____6O2______----------> ___6H20_______ + ___6H2O_____+ ____36ATP_______ 50. In the cellular respiration experiment, you determined metabolic rate by measuring: a) the volume of O 2 produced over time b) the amount of glucose consumed over time c) the volume of O 2 consumed over time d) the volume of CO 2 consumed over time 14

51. Why was the respirometer submerged into water? Why did water move into the respirometer? What is the role of KOH in this experiment? Water moves in because O2 pressure is lower as organisms are consuming the O2. Role of KOH is remove the CO2 Seal the chamber so we can measure the volume of air used KOH absorbs the CO2 and removes it from the chamber so we can see the volume of O2 used up. 52. Explain the effect of germination (versus non-germination) on pea respiration. How do seeds stay alive without leaves and chloroplast? Stored starch and other nutrients feed the embryo. They are using cellular respiration to make ATP: using the stored starch in the seeds. They do not doing photosynthesis 53. Calculate the metabolic rate of 10 crickets that weighed 2.5 gm and consumed 2 ml of oxygen in 6 min. (2 ml O2/6 min)(60 min/h) = (20 ml/h)/2.5 g = 8ml/h/g Metabolic Rate= ( m1 O2/time)=[( 2ml/6 min)( 60 min/h)]/2.5g=8ml/h/g 54. What is the relationship between the body size and metabolic rate? Inverse relationship: the bigger the body. Size the lower the metabolic rate. 55. If respiration of 25gm cold blooded reptile and 25 gm warm blooded mammal at 10 0 C were compared, what results would you expect? Explain The warm blooded mammal would have a higher metabolic rate at this temperature ( much colder than normal body temperature) Metabolic rate would be higher in the warm-blooded mammal. An experiment to measure the rate of respiration in crickets and mice at 10 o C and 25 o C was performed using a respirometer, an apparatus that measures changes in gas volume. Respiration was measured in mL of O 2 consumed per gram of organism over several five-minute trials and the following data were obtained. Temperature Average respiration (mL O 2 /g/min) Cricket Mouse 10 0 C 0.0013 0.0518 25 0 C 0.0038 0.0231 56. According to the data, the crickets at 25 o C have greater oxygen consumption per gram of tissue than do the crickets at 10 o C. This trend in oxygen consumption is the opposite of that in the mice. The difference in trends in oxygen consumption among crickets and mice is due to their: (A)relative size (B) mode of nutrition (C) mode of internal temperature regulation (D)mode of ATP production 57. What is the relationship of metabolism with surrounding temperature in ectothermic and homeothermic animals? Explain your answer. Ectotherms have metabolic rate at low temperature and increase their metabolic as the temperature rises. Homeotherms have higher metabolic rate at low temperatures as they use energy to warm some energy to warm up their bodies 15 http://www.phschool.com/science/biology_place/labbench/lab5/images/crkresp2.gif

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Photosynthesis (6) 58. What is photosynthesis and which organ of the plant carries out photosynthesis? Leaves do photosynthesis. Organelles for cellular respiration: cytoplasm and mitochondria. Organelles photosynthesis: chloroplast 59. Name the organelles where complete cellular respiration and photosynthesis occur 60. Complete the summary equation for Photosynthesis : Carbon dioxide, oxygen, water, sugar, energy(light), chlorohyll ____6CO2_______ + ____6H20_________+ ___Light+Chlorophy11_______----------> ___C6H1206________ + ___602_______ 61. How many pigments did you find in plant leaf extract? Where are the pigments located in What are they? 4 pigments: chlorophyll a, chlorphy11 b, carotenes, xanthophy11. They are in the thylakoids of chloroplast 62. Plant pigments absorb mostly light of violet blue and red colors. Plants perform highest photosynthesis by using wavelengths of _____violet_______color light because it is absorbed____more strongly ______and wavelengths of this color contain highest energy among all other wavelengths of visible light spectrum. 63. Discuss the importance of photosynthesis in the sustenance of life on planet Earth. Why is chlorophyll green? What the absorption spectra tell us about chlorophyll pigment? Produces food and oxygen for all/most aerobc organisms. Also removes CO2. It does not absorbs the green part of the light spectrum ( 500-570 nm) Link for the spectrophotometer used in our lab: https://www.youtube.com/watch?v=kVC3D0pYkR4 How the spectrophotometer works: https://www.youtube.com/watch?v=naaLjuzYME0 64. What are the factors that affect differential movement of pigments by paper chromatography? Paper chromatography was done on a chloroplast extract using acetone as a solvent. At the end of the chromatography it was found that the solvent traveled 20 cm from the origin and a pigment molecule traveled 17 cm from the origin. Calculate the Rf value of the pigment molecule. Rf= dp/ds=17/20=0.85 65. What did we measure to calculate the rate of photosynthesis? Why did we use NaHCO 3 in the experimental set up? 16

66. The following data was collected in your last lab to determine the effect of light intensity on the rate of photosynthesis . Calculate the rate of photosynthesis and plot a graph with the data (identify the dependent and independent variables and don’t forget TAILS). Wattage Total Time Elapsed Amount of Oxygen Produced Rate of photosynthesis (ml of O 2 /hr)) 50 30 min 0.1 ml 0.2 100 15 min 0.1 ml 0.4 200 7 min 0.1 ml 0.86 300 8 min 0.1 ml 0.75 17

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