11 Biology Depth Study: Antibiotic Resistance and Experimental Methodology

Flashcards based on the Year 11 Biology Depth Study booklet, covering experimental design principles, microbiology equipment, antibiotic mechanisms, and bacterial resistance.

Validity

The extent to which an experiment tests what it set out to test, ensuring the effect on the dependent variable is attributed only to the independent variable by controlling all other factors.

Reliability

The extent to which repeated observations or measurements taken under identical circumstances will yield similar, consistent results.

Accuracy

How close the collected data is to the true or known value, achieved by using precise, calibrated measuring equipment to reduce error.

Antibiotics

Medicines used to prevent and treat bacterial infections by targeting essential structures and processes required for survival.

Zone of Inhibition (ZOI)

The clear area surrounding an antibiotic disc on an agar plate where bacterial growth has been prevented; larger zones indicate higher susceptibility.

Agar plate

A Petri dish containing a nutrient-rich gel that allows bacteria to grow so the effectiveness of antibiotics can be observed.

Broth culture

A liquid containing a bacterial species that provides the bacteria to be transferred and spread evenly across an agar plate.

Parafilm

A flexible sealing material wrapped around the edges of agar plates to reduce contamination and prevent accidental opening.

Spreading stick

A tool used to spread bacterial broth evenly across the agar surface to create a consistent bacterial lawn for accurate measurement of zones of inhibition.

Gram-positive bacteria

Bacteria that have a thick cell wall and do not have an outer membrane, such as Bacillus subtilis and Staphylococcus epidermidis.

Gram-negative bacteria

Bacteria that possess an additional outer membrane acting as a protective barrier, making them often less susceptible to some antibiotics; an example is Escherichia coli (E. coli).

Antibiotic Resistance (AR)

Occurs when germs develop the ability to resist the drugs designed to kill them, allowing survivors to multiply and spread resistance traits via DNA.

Penicillin and Ampicillin

Antibiotics that function by targeting and weakening bacterial cell wall synthesis.

Chloramphenicol

An antibiotic that prevents bacteria from producing proteins by targeting bacterial ribosomes.

Efflux pumps

Bacterial resistance mechanisms that remove antibiotics from the cell before they can work.

Resistance enzymes

Adaptations where bacteria produce proteins that break down or change antibiotics, making them ineffective.

Independent variable

The variable that is intentionally changed between experimental groups; in this study, it is the species of bacteria.

Dependent variable

The factor being measured in an experiment; in this study, it is the diameter of the zone of inhibition measured in $\text{mm}$.

Experimental Control (Agar plate with no bacteria)

A trial used to check whether the agar plate, equipment, or working environment has been contaminated; no growth should occur.

Cone of sterility

An area created by the upward current of hot air from a Bunsen burner that prevents airborne contaminants from falling on agar plates.

Aseptic technique

A set of procedures, such as using ethanol and heat sterilization, used to prevent contamination from unwanted microorganisms during an investigation.