Biology

How did varying conditions influence the enzymatic breakdown of egg albumin?

ASSIGNMENT: Please respond to the following questions to complete your laboratory write up. For this assignment you will only focus on your egg white data. Make sure that your write up is accurate, and clearly written so that it is easily readable.

A grading rubric is provided on the third and fourth page of this assignment. To earn a passing C grade on your write up, you must provide answers that align to the “meets” column of the grading rubric. Students wishing to earn B or A grades will take their learning further with the exceeds criteria described in the rubric. There are also some tips at the end of this assignment to help you meet expectations.

FORMAT:

• Type your responses, using 1.5 or double-spacing.

• Include the section headings (Hypothesis, Results, Analysis) and question number (example: 1, 2, 3,etc) in your answers but do not rewrite the question. You may choose to include information about your methodology but that is not a required element of this write up.

• Graphs may be made with a computer program (example: Microsoft excel, Mac numbers, etc) or may be neatly produced with a ruler on graphing paper.

Hypothesis and Prediction – Part 1 of Rubric

1. You should make a prediction about what you thought was going to happen in this experiment and provide the testable explanation or hypothesis on which that prediction is based. You may find it helpful to state your answers to these questions as an “if-then” prediction and because hypothesis. Be sure you have included a biological rationale related in some way to your understanding about the function of enzymes that explains how you arrived at your hypothesis/prediction.

Results – Part 2 of Rubric

2. How did any changes you made to the enzyme solution affect the breakdown of the egg white protein (albumin)? Answer this question by creating a bar graph that shows the results of your experiment. If you need assistance building a graph, there is a Guide to Graphing resource available on your Moodle lab course site.

Analysis- Part 3 of Rubric

3. Explain why you think that the results shown in your graph support or refute your hypothesis (remember we never “prove” anything in science). Consider all your data and the overall data pattern as you answer this question. Don’t ignore unusual data that may not seem to fit into a specific pattern (“outliers”). Explain what you think might be behind these unusual data points.

4. What is the biological significance of your results? What biological concepts explain completely why these events happened in the experiment? How do these results help you understand how molecular reactions are catalyzed by enzymes and what kinds of things affect how enzymes catalyze reactions?

Think about giving a specific example.

References

5. Provide at least one full citation (make sure you include an in-text citation that pinpoints where you used this resource) for a resource you made use of in performing the experiment, understanding the concepts and writing this assignment. Your lab manual must be cited if you refer to it, but you should also use an additional reference, as the lab manual is more a guide to how to conduct the experiment, and other resources will provide additional biological information to help you make sense of your experiment.

If you used more than one resource, you need to cite each one! If you need help with citations, a Guide to Citing References is available on your Moodle lab course site.

Guidelines for Good Quality Scientific Reports

Hypothesis and Prediction: The hypothesis is a tentative explanation for the phenomenon.

• A good hypothesis and prediction is testable (and should be testable under the conditions of our lab environment; for example, if your hypothesis requires shooting a rocket into space, then it’s not really testable under our laboratory conditions).

• Your explanation can be ruled out through testing, or falsified.

• A good hypothesis and prediction is detailed and specific in what it is testing.

• A good hypothesis provides a rationale or explanation for why you think your prediction is reasonable and this rationale is based on what we know about biology.

• A good prediction is specific and can be tested with a specific experiment.

Examples*:

I think that diet soda will float and regular soda will sink.

{This hypothesis misses the goal. It is not specific as we don’t know where the sodas are floating and sinking, and it does not provide any explanation to explain why the hypothesis makes sense}

Because diet soda does not contain sugar and regular soda does, the diet soda will float in a bucket of water, while regular soda will sink.

{This hypothesis approaches the goal. It is more specific about the conditions, and it provides a partial explanation about why the hypothesis makes sense, but the connection between sugar and sinking is unclear}

If diet soda does not contain sugar, then its density (mass/volume) is lower than that of regular soda, which does contain sugar, and so diet soda will float in a bucket of water while regular soda sinks. Understanding the behavior of different liquids may help us understand how fishes control buoyancy. For example, the prevalence of urea in the blood of sharks allows them to adjust their fluid density so that they are able to remain neutrally buoyant in seawater.

{This hypothesis meets the goal. It is specific and the rationale- solutes like sugar or urea affect density and density is what determines floating or sinking in water- is clearly articulated and includes accurate biological information}

If diet soda does not contain sugar, then its density (mass/volume) is lower than that of regular soda which does contain sugar. If we place two sealed, 12 oz. cans of diet and regular cola with equivalent amounts of caffeine into 2 gallons of room temperature distilled water, I expect that the diet soda will float in a bucket of water and the regular soda will sink. This is similar to how the prevalence of urea in the blood of sharks allows them to adjust their fluid density so that they are able to remain neutrally buoyant in seawater. If the amount of sugar in the soda does not influence the density of the soda, then I expect that the sodas will float or sink to the same depth in room temperature water. There are other factors that influence buoyancy. Many teleost fishes, for example, use an air filled space or bladder to maintain buoyancy rather than adjusting the solute concentrations in their body fluids.

{This hypothesis exceeds the goal. It is specific and the rationale is clearly articulated. The specific parameters for testing are clarified and there is a null hypothesis presented of what to expect if there is not an influence due to sugar with a connection to some biological detail that could explain those alternate possible outcomes}

*Note that these examples are for different experiments and investigations and NOT about your write up assignment lab. They are provided only to help you think about what you need to include in your write up.

Graph: The graph is a visual representation of the data you gathered while testing your hypothesis.

• A graph needs a concise title that clearly describes the data that it is showing.

• Data must be put on the correct axes of the graph. In general, the data you collected (representing what you are trying to find out about) goes on the vertical (Y) axis. The supporting data that that describes how, when or under what conditions you collected your data goes on the horizontal (X) axis. (For this reason time nearly always goes on the X-axis).

• Axes must be labeled, including the units in which data were recorded

• Data points should be clearly marked and identified; a key is helpful if more than one group of data is included in the graph.

• The scale of a graph is important. It should be consistent (there should be no change in the units or increments on a single axis) and appropriate to the data you collected

Examples:

{This graph misses the goal. There is no title, nor is there a key to help distinguish what the data points mean; the lines are difficult to distinguish from one another. The scale is too large- from 0 to 100 with an increment of 50, when the maximum number in the graph is 25- and makes it hard to interpret this graph. The x-axis is labeled, but without units (the months) and the y-axis has units, but the label is incomplete- number of what?}

Seasonal changes in population size of three different mad tom catfish in

The Marais de Cygnes River in Spring/Summer 2011

{This graph exceeds the goal. There is a descriptive title that conveys the essence of the hypothesis, and all of the axes well scaled and are clearly labeled with units. There is a key that works in greyscale. The dependent variable (number of individuals) is correctly placed on the y-axis with the independent variable of time placed on the x-axis.

The scale of 0-30 is appropriate to the data, with each line on the x-axis representing an increment of 5.}

Analysis: You need to evaluate your hypothesis based on the data patterns shown by your graph.

You use data to determine support or refute your hypothesis. It is only possible to support a hypothesis, not to “prove” one (that would require testing every possible permutation and combination of factors). Your evaluation of your hypothesis should not be contradicted by the pattern shown by your data.

• Refer back to the prediction you made as part of your hypothesis and use your data to justify your decision to support or refute your hypothesis.

• In the “if” part of your hypothesis you should have provided a rationale, or explanation for the prediction you made in your hypothesis (“then” part of hypothesis”). Use this to help you explain why you think you observed the specific pattern of data revealed in your graph.

• You should consider all of the data you collected in examining the support (or lack of support for your hypothesis). If there are unusual data points or “outliers” that don’t seem to fit the general pattern in your graph, explain what you think those mean.

Examples:

I was right. Diet Pepsi floated and so did Apricot Nectar. Regular Pepsi sank. Obviously the regular

Pepsi was heavier. This helps us understand the concept of density, which is a really important one.

{This analysis misses the goal. The hypothesis isn’t actually mentioned and the data is only briefly described. There is no explanation of the importance of the Apricot Nectar results. Finally, there is no connection to how these results help understand density or why it is biologically important}

I hypothesized that diet soda would float, and all three cans of diet Pepsi did float while the regular

Pepsi sank. This supports my hypothesis. Both types of Pepsi were 8.5 fluid ounces in volume, but the regular Pepsi also contained 16 grams of sugar. This means that the regular Pepsi had 16 more grams of mass provided by the sugar in the same amount of volume. This would lead to an increase in density, which explains why the regular soda cans sank. When we put in a can of Apricot Nectar, which had 19 grams of sugar, it floated. This was unexpected, but I think it is explained by the fact that an Apricot Nectar can had a volume of 7 fluid ounces, but the dimensions of the can are the same as that of a Pepsi can. A same-sized can with less liquid probably has an air space that helped it float. The results of this experiment help us understand how the air bladder of a fish, which creates an air space inside the fish, helps it float in the water and also how seaweeds and other living things with air spaces or other factors that decrease their density keep from sinking to the bottom of the water.

{This analysis meets the goal. It clearly ties the hypothesis to the results and outlines what they mean. It describes how the results support the hypothesis, but also explains a possible reason behind the unusual results of the Apricot

Nectar. Finally, there is a link to how this experiment helps us understand biology}

Another lab table collected results with sodas from the refrigerator and found that their diet Pepsi sank more than our room temperature diet Pepsi. This made us wonder about how temperature influences the density of liquids. We hypothesize that cold liquids are denser than warm ones because the molecules move more closely together. We predict that if we were to take two sodas with the same sugar content and chill one and keep the other at room temperature, the colder soda would sink deeper in room temperature water.

{The additional analysis connected to the meets example above exceeds the goal. It identifies a source of error – changing temperatures- and builds a new hypothesis to test based on that information}

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