Laboratory Equipment and Their Uses

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Questions and Answers

Name one piece of equipment used in the lab and explain how to use it.

Serological pipette, Pasteur pipette, wet mounts on glass slide, spectrophotometer, compound microscope, Eppendorf microcentrifuge

Explain why you would use a serological pipette over a Pasteur pipette or micropipette.

A serological pipette is typically used when you have large volumes and need an exact measurement. You can only dispense up to 1 mL at a time when using micropipettes. While Pasteur pipettes may dispense a bit more than micropipettes, you cannot determine an exact volume dispensed.

What is the total volume in the pipette below? Explain how you were able to determine this.

6.8 mL. We know because the pipette reads 10 in 1/10, which indicates that the entire pipette is 10 mL. If you fill it up all the way to the top (In this case to the 10 line) and each minor tick is 0.1 mL.

If you use the 40X objective on a compound microscope to view a specimen, how would you focus the image and why? What would the total magnification be?

When focusing the image, we want to use the fine focus only to adjust until the image in in focus. This is because the slide is likely very close to the lens. So if we use the coarse focus, it will damage the slide and lens. Total magnification = (Magnification of objective) x (magnification of eye piece). Total magnification = (40) x (10)= 400x Signup and view all the answers

You are conducting an experiment involving an iodine test. You place two drops of each of your samples (including a negative control) into a dry spot-plate and add the iodine solution. You wait a few minutes and you notice a positive result in your negative control. Explain an iodine test determines and how does it work? Also, explain one potential reason for having a positive result in your negative control.

An iodine test determines the presence or absence of starch in a sample. A positive result in the negative control could be caused by contamination. If you accidentally used the same pipette to transfer your negative control and samples containing starch, you may have accidentally contaminated your negative control. Signup and view all the answers

You are given the following table with a list of solutes and their partition coefficients. If you were to place RBCs into each of these solutions and assuming they are all able to cross the RBC membrane, list the solutes in order from fastest to slowest lysis time.

Solute A (0.05) >Solute C (0.003) >Solute B (0.00158) >Solute D (0.00250) Signup and view all the answers

What is the difference between independent and dependent variables? Which of these variables typically go on the x-axis? Which of these variables typically go on the y-axis?

The question is asking you to define independent and dependent variables. Independent variable: Thing(s) that you (as the experimenter) set in the experiment. It is a variable that you think may cause a change in a particular dependent variable. Dependent variable: Variable that "depends" on the independent variable; this is also the variable you are measuring. x-axis: independent variable. y-axis: dependent variable Signup and view all the answers

Is this following statement a research question or hypothesis? Explain your reasoning.

True (A) Signup and view all the answers

What is the effect of temperature on the microbial growth on apples?

Research question because a hypothesis includes a prediction and a rationale for these predictions (e.g., when I do X, Y will increase/decrease/change because of reasons A and B). Signup and view all the answers

In the cell membrane function and structure lab, you added RBCs to various test solutions (e.g,NaCl) and observed lysis time. Explain why you saw lysis in some solutions but not all of them

Permeability and osmosis: RBCs in some solutions lysed because the solution contained solutes that were permeable to the cell so they could have entered the cell causing the cell to swell-> lyse Signup and view all the answers

In the cell membrane function and structure lab, you tested the lysis time at different temperatures. Explain what you used as a negative control in this experiment and why you needed a negative control.

Negative control was a solution where we did not observe lysis due to membrane permeability when RBCs were addded (0.15M NaCl or 0.8M NaCl). We need a negative control because if we do observe lysis, the cells denatured because of high temperature. Signup and view all the answers

Flashcards

Partition Coefficient

A measurement of a solute's relative nonpolarity in a solvent.

Independent Variable

The variable the experimenter changes in an experiment.