Laboratory 3: Chemical Composition of Cells (pp. 27-36) PDF

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Laboratory 3: Chemical Composition of Cells (pp. 27-36). These are both the Post-Lab Questions for Lab 3 and the Pre-Lab Questions for Lab 4....

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Laboratory 3: Chemical Composition of Cells (pp. 27-36) Post-Lab Questions 1. (a) Define organic and inorganic. notice this is a repeat from the prelab questions for this lab. (b) List each of the MOLECULES (NOT FOOD!) in Table 3.7, p. 34, and classify each as organic or inorganic. (a) Organic is defined as a molecule that comes from living things and contains two or more carbons. However, inorganic is defined as a molecule that does not come from living things and are completely absent of carbon. (b) The molecules from Table 3.7 are a. Proteins - Organic b. Lipids - Organic c. Carbohydrates (Starch) - Organic d. Carbohydrates (Reducing Sugar) - Organic 2. (a) If you were to isolate ONLY the plasma membranes of a sample consisting of thousands of cells, what macromolecules would be included in your sample? (Hint: What macromolecules compose the plasma membrane? Consult your lecture notes and textbook chapter 5.) (b) What biochemical assays could you use to detect each of these macromolecule types? (Be specific - which assay for which macromolecule!) (a) If I were to isolate only the plasma membrane of a sample consisting of thousands of cells, the macromolecules that would be included in my sample are proteins, carbohydrates, and lipids. (b) The biochemical assays that could be used to detect each of these macromolecule types are the Benedict test for carbohydrates expressed as reducing sugars, the Iodine test also for carbohydrates that are expressed as starch, the Biuret test for proteins, and the Sudan IV test for lipids. 3. What macromolecule type have we NOT tested for using a biochemical assay in the lab activity today? What technique have we used already in a previous lab that could allow us to visualize the presence or absence of this type of molecule? The macromolecule type that we have not tested for using a biochemical assay are nucleic acids. The technique that we have used already in a previous lab that could allow us to visualize the presence or absence of the this type of molecule would be gel electrophoresis. 4. Suppose you are given orange juice and told to perform a Benedict’s test for reducing sugars. Go back and re-read the methods on p. 29 and look at Table 3.2 to

remember what you would do. Now look at the pictures on p. 36, Interesting Problem #2. (a) Of the 4 tubes pictured, which tube is your experimental and which tube is your negative control to which you compare your experimental? Explain why you chose these 2 tubes. (b) Does orange juice contain reducing sugar? Explain how you arrived at your answer.

(a) The tube that is my experimental is tube #4 because it is the solution that needs to be compared that has already been heated to show the data that is needed for the conclusion. The negative control would be tube #3 because this is the solution before it has been heated which would be compared to show the difference and observe whether or not the solution is a reducing sugar. (b) The orange juice does contain reducing sugar, I arrived at this answer because the positive control, glucose produced the color of a bright orange and when the orange juice was heated with the Benedict added is provided the same color as the positive control and was still different in color from the negative control.

Laboratory 4: Microscope & Cell Observation (pp. 37-56) Pre-Lab Questions 5. What is the total magnification of an object when viewing the object with the 10X (low power) objective lens? The total magnification of an object when viewing the object with the 10x objective lens would be 100x magnification. 6. Explain why observations with a microscope start with the scanning objective and move sequentially up through each objective lens until you reach the highest power? Observations with a microscope start with the scanning objective and move sequentially up through each objective until you reach the highest power because, your field of view is wider which allows you to view the entire specimen, and then you can scan your specimen and find the object that you are looking for and gradually shrink your field of view to focus on the desired area of the specimen and focus it to make it become more visible.

7. What is the difference between the iris diaphragm lever and the condenser? The difference between the iris diaphragm level and the condenser is that the iris diaphragm lever controls the amount of light let through the specimen, while the condenser concentrates the light from the light source toward the specimen.

Benedict’s Test Water

Color No Heat Blue

Color After Heat Blue

Results Negative

Conclusion Absent (no/little reducing sugar)

Glucose

Blue

Cloudy Orange

Positive

Blue Blue Dark Brown Dark Yellow Clear Orange

Negative Negative Positive Negative Positive

Present (lots of reducing sugar) Absent Absent Present Absent Present

Sucrose Blue Starch Blue Onion Juice Light Green Potato Juice Dark Green Unknown Blue Positive Control: Glucose Negative Control: Water .1s are the internal control for the .2s Iodine Test Water

Color Yellow

Result Negative

Glucose Yellow Sucrose Yellow Starch Black Onion Piece Yellow Potato Piece Black/Gray Unknown Black/Gray Positive Control: Starch Negative Control: Water

Negative Negative Positive Negative Positive Positive

Conclusion Absent (not enough starch present) Absent Absent Present Absent Present Present

Biuret Test Color Water Blue Albumin Purple Starch Blue Milk Light Purple Unknown Purple Positive Control: Albumin Negative Control: Water

Result Negative Positive Negative Positive Positive

Conclusion Absent Present Absent Present Present

Sudan IV Test Color Water Smooth Pink Heavy Cream Speckled Orange Coconut Oil Speckled Orange Oil Speckled Orange Unknown Smooth Pink Positive Control: Oil Negative Control: Water

Result Negative Positive Positive Positive Negative

Conclusion Absent Present Present Present Absent

Biuret Test Color Purple Result (+ or -) Positive Unknown is Chicken Broth

Sudan IV Test Smooth Pink Negative

Iodine Test Black/Gray Positive

Benedict’s Test Clear Orange Positive...