Lab 2: Experimental Design, The Scientific Method, and Membrane Permeability

Vocabulary flashcards covering the scientific method, experimental design, variables, controls, replication, plasma membrane composition, and the spectrophotometric study of membrane permeability in Beta vulgaris.

Scientific hypothesis

A tentative explanation that takes all observations into account, which must be both testable and falsifiable.

Working hypothesis

A pragmatic approach to science where, instead of initially exhausting all possible hypotheses, the most plausible one that can be tested is taken first, often due to limited resources such as time, equipment, and funding.

The scientific method / process of science (Figure 2.1)

A non-linear model showing the interconnected components of scientific inquiry: Exploration and Discovery, Forming and Testing Hypotheses, Community Analysis and Feedback, and Societal Benefits and Outcomes.

Peer review

The formal evaluation process that research articles must undergo before being published in scientific journals.

Variables

Characteristics that vary between individuals, such as heart rate, size, or genotype.

Dependent variable (response variable)

What will be measured or recorded in an experiment to understand its variation; it is plotted on the y-axis (vertical axis) when graphed.

Independent variable (explanatory variable)

What is varied during an experiment to observe its effect on the dependent variable; it is plotted on the x-axis (horizontal axis) when graphed.

Constant variables

Any independent variables not being tested that must be kept at the same levels under experimental conditions so their potential influence does not cloud the interpretation of the results.

Levels of treatment

The values or range of amounts selected for an independent variable (such as amounts of fertilizer), chosen based on the experimenter's knowledge of the literature.

Control treatments

Experimental conditions in which the independent variable is either eliminated or set at a standard value, without which generalized conclusions cannot be made.

Replication

The repeating of experimental conditions to address the issue of natural variation among individuals, ensuring that observed differences are not due to chance alone.

Sample size ($n=$)

Defined in this course as the number of replicates per treatment, required to reduce variability in the data and ensure results are reliable.

Reproducibility

The principle that experiments must be carried out and explained clearly enough that another scientist can replicate them and obtain the same or very similar results.

Predictions

Forecasts based on present knowledge about the effect of the independent variable on the dependent variable, often taking the form: 'if the hypothesis is true, then the results of the experiment will be….'

Plasma membrane

A selectively permeable boundary surrounding all cells that regulates the passage of materials into and out of the cell, composed of phospholipid bilayers, proteins, and carbohydrates.

Plasma membrane diagram (Figure 2.2)

A structural diagram representing the cell boundary, showing the phospholipid bilayer, embedded and surface proteins, and external carbohydrates.

Beta vulgaris

The scientific name for the common garden beet, whose storage root cells are used to study membrane permeability.

Betacyanin

A red-violet betalain pigment dissolved in the cell sap of beet root vacuoles.

Betaxanthin

A yellow-orange betalain pigment dissolved in the cell sap of beet root vacuoles.

Tonoplast

The vacuolar membrane that separates the contents of the vacuole from the cytoplasm, normally impermeable to betalain pigments.

Spectrophotometry

A technique used to measure the proportions of light of different wavelengths absorbed and transmitted by a pigment solution by passing a beam of light of a particular wavelength through it.