Lab Quiz #1 Study Set

How do you know the tests worked well? (Lab 2 Organic Molecules)

A way to know if the tests worked well is to use positive and negative controls. In this experiment, each test tested a positive and negative control. I am confident that each test worked well because of the use of positive and negative controls throughout the experiment.

Would you feel confident with your results if you only had positive controls and no negative controls? Why or why not?

I would not feel confident with my results if I only had positive controls and no negative controls. After all, a negative control informs the researcher what a negative result looks like. Without negative controls, researchers are unable to compare and most importantly confirm that there are no false positive results during an experiment.

In Experiment 2: Concentration of the dye and distance of diffusion: What is the independent variable? Dependent variable? 3 standardized variables? (Lab 1 Exp Design)

Independent variable: The concentration of the dye. Dependent variable: The distance of diffusion. 3 standardized variables: 1) Pre-cut piece of filter paper (16mm), 2) 4% Potassium permanganate dye, 3) Agar plate.

In Experiment 1: Molecular weight of the dye and distance of diffusion: What is the independent variable? Dependent variable? 3 standardized variables? (Lab 1 Exp Design)

Independent variable: The molecular weight of the dye. Dependent variable: The distance of diffusion. 3 standardized variables: 1) Pre-cut piece of filter paper (16mm), 2) 4% Potassium permanganate dye, 3) Agar plate.

In Experiment 3: Temperature and distance of diffusion: What is the independent variable? Dependent variable? 3 standardized variables? (Lab 1 Exp Design)

Independent variable: The temperature of each dye. Dependent variable: The distance of diffusion. 3 standardized variables: 1) Pre-cut piece of filter paper (16mm), 2) 4% Potassium permanganate dye, 3) Agar plate.

What is a positive control? (Lab 2 Organic Molecules).

It contains the variable for which you are testing. A positive reaction to a positive control demonstrates that your test is working. A positive control also demonstrates what a positive result looks like.

What is a negative control? (Lab 2 Organic Molecules).

It does not contain the variable for which you are searching. It contains only the solvent (often distilled water with no solute) and does not react in the test. A negative control demonstrates what a negative result looks like.

What does the control group do? (Lab 1 Exp Design)

It ensures that the experiment works as it is supposed to. Without a control, it can lead to experimental bias, the favoring of certain outcomes over others.

What is an independent variable? (Lab 1 Exp Design)

It is a controlled variable or factor whose levels are set by the researchers but isn't changed by the other variables you are trying to measure.

What is a controlled experiment? (Lab 1 Exp Design)

It is one that is designed to compare an experimental group with a control group.

What is a dependent variable? (Lab 1 Exp Design)

It is the factor being measure that is predicted to be affected by the independent variable.

What is the relationship between molecular weight and diffusion? (Lab 1 Exp Design)

Molecular weight and diffusion share an indirect relationship with one another. The greater the molecular weight, the slower the rate of diffusion. In other words, lighter particles diffuse more quickly, resulting in a greater distance of diffusion.

What is the relationship between temperature and diffusion? (Lab 1 Exp Design)

Temperature and diffusion share a direct relationship. The higher the temperature, the higher the kinetic energy, which results in a greater distance of diffusion.

How do you test for a reducing sugar (carbohydrates)? How does this test work? What does a positive result looks like? (Lab 2 Organic Molecules)

Test: Benedict's Test How: The Benedict's test identifies reducing sugars by reducing the Copper (II) ions to Copper (I) oxide at basic pH (High). Positive Result: Blue (none), Green (Less), Orange (More), Brick-red (most)

How do you test for a protein? How does this test work? What does a positive result looks like? (Lab 2 Organic Molecules)

Test: Biuret Test How: The amino group on one amino acid is linked to the carboxyl group on an adjacent amino acid by a peptide bond. This bond is the site of action for the Biuret test for protein. The Biuret reagent contains Copper (II) sulfate and complexes with the peptide bond producing a violet color. Positive result: A violet color is a positive test for the presence of protein; the intensity of color relates to the number of peptide bonds that react. A Copper (II) ion must complex with at least two to four peptide bonds to produce a color (free amino acids and very short chains do not react positively). Pink color (none).

How do you test for starch? How does this test work? What does a positive result looks like? (Lab 2 Organic Molecules)

Test: Iodine Test How: Since starch is a coiled polymer of glucose, iodine interacts with these coiled molecules and becomes bluish black. Positive result: Bluish black (+), Yellowish brown (No reaction)

How do you test for a lipid? How does this test work? What does a positive result looks like? (Lab 2 Organic Molecules)

Test: Sudan IV test How: Tests for lipids are based on a lipid's ability to selectively absorb pigments in fat-soluble dyes such as Sudan IV. Lipids will stain any lipid layer that separates from water. Positive result: Separate, red-staining layers.

What is the relationship between the concentration of the dye and diffusion? (Lab 1 Exp Design)

The concentration of the dye and diffusion share an direct relationship. The higher the concentration of the dye, the greater the distance of diffusion.

Explain why the plate incubated at room temperature was necessary. (Lab 1 Exp Design)

The plate incubated at room temperature was necessary to serve as the control group for this experiment. This is important because it serves as a "baseline" and helps eliminate "experimental bias".

What are standardized variables? (Lab 1 Exp Design)

They are variables that are kept consistent in all groups so that any changes in the dependent variable can be attributed to changes in the independent variable.

What is a treatment? (Lab 1 Exp Design)

Treatment is something that researchers administer to experimental units. Ex): a teacher practices different teaching methods on different groups in her class to see which yields the best results.