Mix of multiple choice, true/false, and fill-in-the-blank
Instant feedback after each question
Unlimited attempts for practice
Estimated time: 25–30 minutes
QUESTION 1
Which of the following is NOT considered essential personal protective equipment (PPE) in a biochemistry lab?
✅ Correct! While face masks may be needed for certain procedures (e.g., handling powders), the essential PPE always required is lab coat, safety goggles, and gloves. Face masks are not considered universal PPE for all lab work .
QUESTION 2
How many grams of NaCl (MW = 58.44) are needed to prepare 500 mL of 0.2 M NaCl?
✅ Correct! moles = M × L = 0.2 × 0.5 = 0.1 mol. mass = 0.1 mol × 58.44 g/mol = 5.844 g ≈ 5.84 g .
QUESTION 3
You have a 5 M NaCl stock solution. How many mL of stock are needed to prepare 250 mL of 0.15 M NaCl?
✅ Correct! The Beer-Lambert law is A = εcl, where A = absorbance, ε = molar extinction coefficient, c = concentration, l = path length .
QUESTION 5
A solution of NADH has absorbance 0.35 at 340 nm in a 1 cm cuvette. The molar extinction coefficient of NADH at 340 nm is 6220 M⁻¹cm⁻¹. What is the concentration of NADH?
✅ Correct! c = A/(εl) = 0.35/(6220 × 1) = 5.63 × 10⁻⁵ M = 56.3 μM .
QUESTION 6
In paper chromatography, the Rf value is calculated as:
✅ Correct! Rf = distance traveled by compound / distance traveled by solvent front. Rf values are characteristic for each compound under specific conditions .
QUESTION 7
One International Unit (U) of enzyme activity is defined as:
✅ Correct! One International Unit (U) is the amount of enzyme that catalyzes the conversion of 1 micromole of substrate per minute under specified conditions .
QUESTION 8
An enzyme extract has activity of 0.45 U/mL and protein concentration of 1.5 mg/mL. What is the specific activity?
✅ Correct! Specific activity = activity / protein concentration = 0.45 U/mL ÷ 1.5 mg/mL = 0.3 U/mg protein .
QUESTION 9
In Michaelis-Menten kinetics, Km represents:
✅ Correct! Km (Michaelis constant) is the substrate concentration at which the reaction velocity is half of Vmax. It indicates the affinity of the enzyme for its substrate .
QUESTION 10
The Bradford protein assay measures absorbance at what wavelength?
✅ Correct! The Bradford assay uses Coomassie Brilliant Blue G-250, which shifts from 465 nm to 595 nm upon binding to protein. Absorbance is measured at 595 nm .
QUESTION 11
Which chromatographic technique would be most appropriate for analyzing the fatty acid composition of niger seed oil?
✅ Correct! Gas chromatography (GC) is the method of choice for fatty acid analysis. Fatty acids are first converted to methyl esters (FAMEs) to make them volatile, then separated by GC .
QUESTION 12
A handheld refractometer measures which quality parameter in the field?
✅ Correct! A refractometer measures Brix (soluble solids content, primarily sugars). It's a simple, portable tool for assessing fruit maturity and quality in the field .
QUESTION 13
What is the minimum Brix typically required for export mangoes?
✅ Correct! Most export markets require mangoes to have a minimum Brix of 12° for acceptable sweetness and quality .
QUESTION 14
For Hass avocados, what parameter is often used as an indicator of maturity and oil content?
✅ Correct! For Hass avocados, dry matter (≥21%) is used as an indicator of oil content and maturity. Dry matter correlates well with oil content and is easier to measure than oil directly .
QUESTION 15
To analyze the volatile aroma compounds that distinguish Yirgacheffe coffee from other Ethiopian coffees, which analytical technique would be most appropriate?
✅ Correct! GC-MS (Gas Chromatography-Mass Spectrometry) is ideal for analyzing volatile compounds. It separates volatile components by GC and provides mass spectra for identification, allowing researchers to characterize the unique aroma profiles of different coffee origins .
📊 Module V Complete!
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📌 Module V Complete!
You have completed all units in Module V: Analytical & Biochemical Techniques. You should now be able to: