Practice Test Geeks(STP) Scientist Training Programme Practice Test
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Technical Skills & Application Flashcards

7 cards from real STP practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 7 Technical Skills & Application flashcards as text

  1. A laboratory result shows an unexpectedly high potassium level of 7.2 mmol/L from a routine blood sample. What is the first pre-analytical variable to investigate?

    Answer: Haemolysis of the sample

    Haemolysis releases intracellular potassium from red blood cells, causing falsely elevated plasma potassium readings.

  2. In flow cytometry, what property of cells does forward scatter (FSC) primarily measure?

    Answer: Cell size (relative volume)

    Forward scatter correlates with cell size because larger cells diffract more laser light in the forward direction.

  3. Which technique is used to separate proteins based solely on their isoelectric point (pI)?

    Answer: Isoelectric focusing (IEF)

    In IEF, proteins migrate through a pH gradient until they reach the pH at which their net charge is zero (their pI), effectively separating them by pI.

  4. A scientist records duplicate OD readings of 0.452 and 0.468 for the same sample. What is the percentage difference between these readings?

    Answer: 3.5%

    Percentage difference = |0.468 − 0.452| / ((0.468 + 0.452)/2) × 100 = 0.016/0.46 × 100 ≈ 3.5%.

  5. In ELISA, what is the function of the enzyme-conjugated secondary antibody?

    Answer: It amplifies the signal by reacting with a substrate to produce a detectable product

    The enzyme (e.g., HRP) conjugated to the secondary antibody converts a substrate into a coloured, fluorescent, or luminescent product, amplifying the detection signal.

  6. When should internal quality control (IQC) samples be run in a clinical laboratory?

    Answer: At the start of each analytical run alongside patient samples

    IQC samples are run within every analytical batch to monitor the performance of the assay in real time and detect errors before patient results are released.

  7. Which centrifugation principle is used to separate subcellular organelles by their density rather than their size?

    Answer: Isopycnic (equilibrium density-gradient) centrifugation

    In isopycnic centrifugation, particles migrate until they reach the point in the gradient where their buoyant density equals that of the surrounding medium, separating by density.