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Biology 1510: Lab Exam I Name: _______________________________ Time Limit: 75 minutes Instructions: During this examination, you may not consult notes, cell phones, books, or fellow students. Write as legibly as you can. Lab instructor cannot answer any questions during the test; if the instructions are unclear, just do the best you can. Prior to the test, seating arrangements will be determined by lab instructor. Answers will be posted within 24 on instructor's website. Scores will be graded on a curve. Lipids [13 pts] 1. You have been given a liquid containing fatty acids. You perform TLC (thin layer chromatography) on it with the results shown on the left. a. How many individual fatty acids are present in this sample? [1 pt] 3 fatty acids b. What is the Rf value of each of the fatty acids in this sample? [2 pts] a = 4/10 = 0.4 b= 7/10 = 0.7 c= 9/10 = 0.9 c. All things being equal, which fatty acid is least soluble in this TLC system? [1 pt] sample a (OR) the one that traveled the least (OR) the one with Rf = 0.4 d. Please identify, with arrows and labels, the origin [1 pt] and the solvent front [1 pt] of this chromatogram? X at bottom; thick black line on top 2. My friend Joe gave me 2g of a substance, which he claims is a lipid. He also gave me a plain peace of paper, a beaker of water, 2 g of table sugar-- and nothing else. Describe in detail 4 simple tests [1 pt each] which would allow me to decide whether the substance is indeed a lipid. In each of these tests, what would the control be? 1. Greasy. Check sugar--it' not greasy. 2. Translucent when raised against light. Control: sugar isn't. 3. Water insoluble. Spread a bit of the fat on paper, and a bit of sugar some distance away. Drop of water on both. 4. Lipids float on water; sugar sinks or dissolves 3. Circle one (a total of 3 circles) in each underlined group: A reaction joining a triglyceride to 1 /2 /3 / 4 / 5 /6 fatty acids / Benedict / monosaccharide / DNA releases / takes up / evaporates / liquefy water molecules. [1 pt] 3 / fatty acids / releases 4. Fill in the blanks: Saturated lipids contain all the _________ atoms they can possibly have [1 pt] Hydrogen 5. T/F: Molecule per molecule, carbohydrates store less energy than lipids True / False [1 pt] True Carbohydrates / Nature of Science [17 pts] 1. The carbohydrates lab involved three tests--Benedict for reducing sugars, Barfoed for monosaccharides, Iodine for some polysaccharides. Use the following chart to answer questions a through c. Sample A Sample B Sample C Benedict Test (+) (-) (-) Barfoed Test (+) (-) (-) Iodine Test (-) (-) blue-black a. Is Sample A glucose, maltose, sucrose, glycogen or amylose (from starch)? [1 pt] reducing, monosaccharide, non-polysaccharide = glucose b. Is Sample B glucose, maltose, sucrose, glycogen or amylose (from starch)? [1 pt] non-reducing, non-monosaccharide, nonpolysaccharide = sucrose c. Is Sample C glucose, maltose, sucrose, glycogen or amylose (from starch)? [1 pt] non-reducing, non-monosaccharide, branched polysaccharide = amylose 2. Fill in 5 blanks: How does the Benedict reaction work? [2 pts] ______ 1 ( /2 pt) in the Benedict reagent reacts with free _______ or ___________ groups (1/2 pt), turning from blue to _____ (1/2 pt) when ________ (1/2 pt) copper / aldehyde or ketone / red / heated Fill in 2 blanks: Honey gives a positive reaction in the ___________ [1 pt] Test because it is chiefly comprised of ______________ [1 pt] Barfoed, Monosaccharides 3. 5. After we obtained a positive result in the iodine test with glycogen, we boiled the solution. a. What happened to the color? b. Why? [1 pt] Color faded somewhat. Iodine assembles with the coils of poly-s. Boiling the solution breaks the coils. [1 pt] 6. Fill in 2 blanks: The active positive ingredient of the Benedict Test which gives the reagent its blue color, and which changes to a different color in positive reactions is ____________ [1 pt]. When this ingredient actually changes color, it does so because it gains an ______________. [1 pt] Copper (or Cu++) / electron 7. Fill in 1 blank: Give one example of a monosaccharide: ___________________ [1 pt] (glucose, fructose, galactose . . .) 8. Fill in the blanks: Carbohydrates are composed of carbon, ________ and oxygen in a _____ : _____ : ______ ratio [1 pt] hydrogen; 1:2:1 9. T/F: The glucose molecule is larger than the amylose molecule True/ False [1 pt] F 10. I believe that colony collapse disorder in bees is caused by the widespread use of genetically modified plants. So I take 1000 bees, feed them exclusively on pollen and nectar taken from genetically-modified crops, and observe that, in 2 days, 950 bees are dead. I then submit a paper for publication, claiming that I did, at long last, found the causes for this disorder. To my horror, the paper is rejected on the grounds that it doesn't prove my hypothesis, along with a suggestion that I repeat the experiment-- with some modifications. a. In this case, what was my hypothesis? [1 pt] c. What might be the editor's suggestion? What problem does it solve [2 pts] Hypothesis: genetically modified plants cause colony collapse disorder. The experiment needs controls. At the very least, I should take another 1,000 bees and feed them on the exact same plants, but which have not been genetically modified. Amino Acids and Proteins [9 pts] 1. Use the TLC sheet to the left to answer questions a and b below. In this sheet, each linear division is equal to 1 cm. a. What is the Rf value for the sample with origin A? [1 pt] 0.4 b. Knowing that the Rf value of alanine is 0.6, please circle any of the spot(s) containing alanine, if any (don't guess--any incorrect circle -1 points) [2 pts] C and F contain alanine 2. Circle one number: The ninhydrin test must be complemented by thin layer chromatography because: 1. The ninhydrin doesn't color the amino acids 2. The ninhydrin test produces yellow color in a proline sample 3. The colors of 2 or more different amino acids in the ninhydrin test may be indistinguishable 4. thin layer chromatography requires a solvent [1 pt] 3 3. Fill in the blanks: All amino acids have an identical___________ group and an identical _____________ group [1 pt] Amine / carboxyl 4. Fill in the blanks: The C and N atoms of two amino acids connect to form a (give scientific name, not C-N) ___________ bond. [1 pt] peptide 5. Circle twice: When a dipeptide breaks down into its two constituent molecules, it does so by releasing / taking up / absorbing / breaking / recharging one molecule of polypeptide / nitrogen / water/ peptide bond / biuret [1 pt] taking up / water 6. T/F: A protein (e.g., insulin) is made up of one or more chains of glucose molecules. [1 pt] F; different amino acids 7. T/F: Unlike glycine and proline, the amino acid alanine has an R group. [1 pt] F; every amino acid has an R group Writing a Lab Report [8 pts] 1. The following lab report information should be included in which of the following 4 parts: Introduction, Materials and Methods, Results, Discussion: a. Glucose, galactose and fructose exhibited positive Benedict tests. -->Lab Report Part is ____________ [1 pt]. Results, indicates test result for three sugars b. The color change in the starch sample indicates that it contains amylose. -->Lab Report Part is ____________ [1 pt] Discussion, explains the results 2. The following paragraph has been taken from the Introduction section of a Student's lab report. This paragraph breaks three rules of proper scientific writing. Circle each rule-breaking sentence, explain why it does not belong in the introduction section, and suggest a more proper placement for it. (Remember: Here you are looking for scientific writing errors, not for errors of fact, interpretation, grammar, or spelling!) [2 pts each, 1 for error, 1 for explanation and correct placement, for a total of 6 points] Carbohydrates can be classified as monosaccharides, disaccharides, or polysaccharides. In the Benedict test, glucose, galactose and fructose all turned red while sucrose remained blue. Sucrose is, therefore, a non-reducing sugar while glucose, galactose and fructose are reducing sugars. Two other tests were performed according to the procedures in the Carbohydrates exercise found in Experiments in Biology: from Chemistry to Sex by Linda R. Van Thiel. These were the Barfoed test to identify monosaccharides and the Iodine test to identify polysaccharides. In the Benedict test, glucose, galactose and fructose all turned red, while sucrose remained blue in color - should be in the Results Sucrose is, therefore, a non-reducing sugar while glucose, galactose and fructose are reducing sugars - should be in the Discussion Two other tests were performed according to the procedures in the Carbohydrates exercise found in Experiments in Biology: from Chemistry to Sex by Linda R. Van Thiel - should be in the Materials and Methods The Microscope [15 pts] 1. In the paragraph below, a student broke three rules of handling and/or operating a light microscope. Circle each mistake and replace it with the proper procedure. ( Note: your answer should be based on the errors written out below--not on missing information!) [3 pts] Fatima Aziz wanted to examine a slide of Paramecium. Using the microscope, she placed the slide on the stage, turned the highest power objective, and began to focus. When she couldn't see anything, she changed to the 43X high dry objective lens, placed a drop of oil on the slide, and tried focusing with the fine adjustment. When she was done, she turned off the light, removed the slide, cleaned the oil off the slide and the lens, and clicked the highest power objective in place. She then turned the focus knob so the objective was as close to the stage as it could get, safely unplugged the scope, loosely wrapped the cord, and returned the scope to the cabinet. started focusing with high power (start at low) used oil with high dry lens (use oil only with oil lens) when done clicked high power objective in place (should put away with lowest power in place) 2. Fill in the blanks: If your field of view, while looking at the dissecting microscope, is 12.56 mm2, and you are observing an organism that just about extends from the periphery of your field of view to its center, how long is that organism?___________ [2 pts] 2 (22X3.14=12.56; so the radium is 2) 3. Your lab manual describes three principles of the cell theory. One of these principles claims that "all cells arise from pre-existing cells." Describe and explain one classical experiment (from Raven's Biology; also mentioned in our lab) which lends support to this principle. [2 pts] Here you need to describe Pasteur's elegant experiment on spontaneous generation, and explain why it lends support to the pre-existence principle 4. T/F: Resolution describes the ability to see two lines as separate lines. true / false [1 pts] answer: true 5. Circle correct answer(s): Chlorophyll is absent from: maple leaves / dog cheek cells / leaves of elodea / leaves of grass / blue-green algae [1 pt] answer: dog cheek cells 6. T/F: Among other things, the cell theory claims that all organisms are composed of cells. True / False [1 pt] Answer: True 7. Circle 2 correct answers: Blue-green algae obtain their energy requirements directly from fungi / sunlight / DNA / RNA / Leaves of grass / Ocean waves while animals obtain their energy by eating other animals or by eating plants / mitochondria / fungi / microscopes / classification schemes [2 pts] 8. Fill in the blanks: In a microscope, the distance from the objective to the cover slip is called: ______________ _________________ [1 pt] working distance 9. Circle one: You placed the green letter e in your microscope right-side up, and when you looked at through the eyepiece, it appeared right-side up / sideways / illegible / red / upside down / refracted [1 pt] Upside down 10. Circle twice: The wider / more focused / more separable / lower the magnification, the larger / smaller / more circular / narrow is the field of view [1 pt] Lower/ larger Prokaryotes [13 pts] 1. Geeta wanted to gram stain some bacteria she found growing on her old spaghetti. She couldn't find any safranin, but was able to get hold of neutral orange. A call to her Bio 1510 lab instructor assured her that the two stains served the exact same function in the Gram staining procedure. So, when she carried out the gram staining procedure and looked at her slide, she saw two types of organisms. One was spherical and orange in color, the other was purple and rod-shaped. a. pts] What is the shape and color of the gram positive bacterium? [2 purple, rod-shaped b. What was the gram reaction of the coccus? [1 pt] gram negative c. alcohol? What color would the G- bacteria have been if she didn't add the [ pts]Why? [ pts] purple; the alcohol decolorizes G- bacteria 2. Circle one: Crystal violet is used in the Gram staining protocol to make visible the: G+ bacteria / iodine / G- bacteria / mordant / G neutrality / safranin / cover slip [1 pt] Answer: G+ 3. Fill in the 2 blanks: Alcohol in the gram staining protocol is used to ___________________ the gram _________ bacteria [2 pts] decolorize / negative 4. Fill in the 4 blanks: Eukaryots are comprised of the following 4 major groups: ___________ ___________ _______________ ________________ [2 pts] animals, plants, fungi, protists 5. Fill in the 2 blanks: One useful classification scheme of bacteria involves their _____________ [1 pt]. Another useful classification scheme involves the ____________ __________ procedure. [1 pt]. Thus, your class observations showed that E. coli may be classified as a _________________ _________________ _______________ [1 pt] Shape / gram-staining / gram-negative / bacillus

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