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BACE: Equipment & Experimental Design Practice Questions & Answers

40 Questions·Free Practice·MCQ with Explanations

Badge: Standard Equipment & Experimental Design

Type: Practical | Weight: 15% of Exam

Combines equipment operational knowledge with the logic required to design valid experiments.

Equipment Topics:

Centrifuge balancing and Rotor types.
Spectrophotometer operation.
Autoclave cycles and Microscope care.

Design Topics:

Experimental controls (+/-) and Replicates.
Lab Notebook legal standards.
Error Analysis & PCA (Principal Component Analysis).

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When operating a centrifuge, which of the following practices is critical to prevent damage to the drive shaft and potential injury?

Setting the timer to at least 10 minutes
Ensuring the rotor is balanced by placing tubes of equal mass opposite each other
Using glass tubes for speeds above 20,000 RPM
Setting the temperature to 4°C for all spin cycles

View Answer & Explanation

Correct Answer: Option B -

Ensuring the rotor is balanced by placing tubes of equal mass opposite each other

Explanation:

Centrifuges must be balanced to distribute the load evenly around the rotor. An unbalanced rotor can cause the centrifuge to wobble, damaging the drive shaft and potentially causing catastrophic failure. Source: Eppendorf Centrifugation Basics.

A technician needs to autoclave 500 mL of liquid media. Which autoclave cycle parameters are appropriate to prevent the liquid from boiling over during the exhaust phase?

Gravity cycle with fast exhaust
Vacuum cycle with fast exhaust
Liquid cycle with slow exhaust
Flash cycle with zero exhaust time

View Answer & Explanation

Correct Answer: Option C -

Liquid cycle with slow exhaust

Explanation:

The 'Liquid' cycle uses a slow exhaust (or gravity displacement with slow vent) to allow the pressure to decrease gradually. A fast exhaust would cause the superheated liquid to boil over violently due to the rapid drop in pressure.

In a spectrophotometry experiment, what is the primary purpose of a 'blank' sample?

To calibrate the wavelength accuracy of the machine
To measure the absorbance of the analyte of interest
To increase the sensitivity of the detector
To zero the absorbance reading by accounting for the solvent and reagents

View Answer & Explanation

Correct Answer: Option D -

To zero the absorbance reading by accounting for the solvent and reagents

Explanation:

A blank contains everything in the sample except the analyte of interest. It is used to zero the instrument ( $A=0$ ), ensuring that the measured absorbance is due solely to the analyte and not the solvent or cuvette.

Calculate the Relative Centrifugal Force (RCF) or 'g-force' if the rotor radius ( $r$ ) is 10 cm and the speed is 3000 RPM. Use the approximation formula: $RCF = 1.12 \times 10^{-5} \times r \times (RPM)^2$

~1,008 g
~3,024 g
~336 g
~10,080 g

View Answer & Explanation

Correct Answer: Option A -

~1,008 g

Explanation:

Calculation: $RCF = 1.12 \times 10^{-5} \times 10 \times (3000)^2$ $RCF = 1.12 \times 10^{-4} \times 9,000,000$ $RCF = 1.12 \times 900 = 1008 \; g$ .

Which of the following describes a Negative Control in a PCR experiment?

A sample containing DNA known to have the target sequence
A reaction mix with water substituted for the DNA template
A sample run at a different temperature to test robustness
A replicate of the experimental sample

View Answer & Explanation

Correct Answer: Option B -

A reaction mix with water substituted for the DNA template

Explanation:

A negative control (often 'No Template Control' or NTC) contains reagents but no target DNA. If amplification occurs, it indicates contamination.

You need to pipette 15 $\mu$ L of a reagent. Which pipette would provide the highest accuracy and precision?

P1000 (Range: 100-1000 $\mu$ L)
P200 (Range: 20-200 $\mu$ L)
P20 (Range: 2-20 $\mu$ L)
P10 (Range: 0.5-10 $\mu$ L)

View Answer & Explanation

Correct Answer: Option C -

P20 (Range: 2-20 $\mu$ L)

Explanation:

Pipettes are most accurate in the upper range of their capacity. A P20 (2-20 $\mu$ L) is ideal for 15 $\mu$ L. A P200 is less accurate at its lower limit, and a P10 cannot hold 15 $\mu$ L.

According to legal standards for Lab Notebooks, how should an error be corrected?

Use white-out or correction fluid to cover the mistake completely
Tear out the page and rewrite the data on a fresh page
Draw a single line through the error, then initial and date the correction
Scribble over the error until it is illegible

View Answer & Explanation

Correct Answer: Option C -

Draw a single line through the error, then initial and date the correction

Explanation:

GLP (Good Laboratory Practice) requires that original data remain legible. Errors must be crossed out with a single line, corrected, initialed, and dated to maintain an audit trail.

When using a light microscope with an oil immersion objective (100x), why is immersion oil required?

To lubricate the slide and prevent scratching the lens
To match the refractive index of glass, preventing light scattering and increasing resolution
To cool the objective lens during high-intensity illumination
To stain the specimen for better contrast

View Answer & Explanation

Correct Answer: Option B -

To match the refractive index of glass, preventing light scattering and increasing resolution

Explanation:

Immersion oil has a refractive index (~1.51) similar to glass. It bridges the gap between the slide and the lens, preventing light refraction (bending) that would occur in air, thus increasing the Numerical Aperture and resolution.

A student measures the absorbance of a solution three times and gets: 0.45, 0.46, and 0.45. The true value is 0.80. How would you describe these results?

High accuracy, low precision
High accuracy, high precision
Low accuracy, high precision
Low accuracy, low precision

View Answer & Explanation

Correct Answer: Option C -

Low accuracy, high precision

Explanation:

The values are very close to each other (high precision/reproducibility) but far from the true value of 0.80 (low accuracy).

Which of the following best defines Principal Component Analysis (PCA)?

A method to sequence DNA fragments rapidly
A statistical technique used to reduce the dimensionality of large datasets while preserving variance
A protocol for validating autoclave sterility
A calculation for determining the molarity of a solution

View Answer & Explanation

Correct Answer: Option B -

A statistical technique used to reduce the dimensionality of large datasets while preserving variance

Explanation:

PCA is a dimensionality reduction technique that transforms a large set of variables into a smaller one (principal components) that still contains most of the information (variance) in the large set.

BACE: Equipment & Experimental Design Practice Questions & Answers

Badge: Standard Equipment & Experimental Design

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