BE/B Eng Bachelor of Engineering Bachelor of Biomedical Engineering 5 — Questions and Answers
Question 1: Which principle governs the diffusion of oxygen from alveoli into pulmonary capillaries?
- Starling's law of the heart
- Fick's law of diffusion (Correct answer)
- Poiseuille's law of viscous flow
- Laplace's law of wall tension
Correct answer: Fick's law of diffusion
Fick's law states that the net diffusion rate of a gas across a membrane is proportional to the surface area, the concentration (partial pressure) gradient, and the membrane's diffusion coefficient, and inversely proportional to membrane thickness.
Question 2: When designing a bioreactor for tissue engineering, which environmental parameter is NOT typically monitored and controlled?
- pH and dissolved oxygen concentration
- Mechanical stimulation (shear stress or cyclic strain)
- Gravitational field strength (Correct answer)
- Temperature and CO₂ concentration
Correct answer: Gravitational field strength
Bioreactor design focuses on controlling biochemical parameters (pH, O₂, CO₂) and mechanical stimuli (perfusion, compression, rotation), but gravitational field strength is a fixed environmental constant that is not actively controlled in standard lab bioreactors.
Question 3: In the context of ISO 10993, biocompatibility testing of a medical device evaluates the material's potential to cause:
- Only mechanical failure under physiological loading conditions
- Adverse biological responses including cytotoxicity, sensitization, and genotoxicity (Correct answer)
- Electromagnetic interference with other medical devices
- Dimensional changes due to thermal expansion during sterilization
Correct answer: Adverse biological responses including cytotoxicity, sensitization, and genotoxicity
ISO 10993 is a series of standards that defines biological evaluation tests—such as cytotoxicity, sensitization, irritation, systemic toxicity, and genotoxicity—to assess if a medical device or its materials could harm patients.
Question 4: In biomedical optics, the 'therapeutic window' refers to the range of wavelengths that:
- Are optimal for fluorescence microscopy of fixed histological sections
- Penetrate tissue most deeply due to minimal absorption by water, hemoglobin, and melanin (Correct answer)
- Cause maximal absorption in the retina for photodynamic therapy
- Are used exclusively for UV sterilization of medical instruments
Correct answer: Penetrate tissue most deeply due to minimal absorption by water, hemoglobin, and melanin
The near-infrared therapeutic window (~650–1350 nm) is the spectral region where tissue scattering and absorption by major chromophores (water, oxy/deoxyhemoglobin, melanin) are minimized, allowing the deepest light penetration.
Question 5: A biomedical engineer is reviewing a receiver operating characteristic (ROC) curve for a diagnostic test. What does the area under the curve (AUC) represent?
- The threshold probability that maximizes sensitivity alone
- The overall ability of the test to discriminate between diseased and non-diseased populations (Correct answer)
- The positive predictive value of the test at the optimal threshold
- The ratio of true positives to false positives at a single operating point
Correct answer: The overall ability of the test to discriminate between diseased and non-diseased populations
The AUC of a ROC curve is a single scalar value summarizing the test's discriminative ability across all possible thresholds; an AUC of 1.0 is perfect discrimination, while 0.5 represents chance-level performance.
Question 6: What is the primary function of the sodium-potassium pump (Na⁺/K⁺-ATPase) in maintaining the resting membrane potential of a cell?
- Passively equilibrating Na⁺ and K⁺ concentrations across the membrane down their electrochemical gradients
- Actively transporting 3 Na⁺ out and 2 K⁺ into the cell per cycle, maintaining concentration gradients (Correct answer)
- Opening voltage-gated channels to allow rapid ion flux during an action potential
- Generating ATP from the electrochemical gradient created by mitochondrial respiration
Correct answer: Actively transporting 3 Na⁺ out and 2 K⁺ into the cell per cycle, maintaining concentration gradients
The Na⁺/K⁺-ATPase uses ATP to actively transport 3 sodium ions out and 2 potassium ions in per cycle, maintaining the steep ionic concentration gradients that underlie the resting membrane potential.
Question 7: In finite element analysis (FEA) of a bone implant, what does 'mesh convergence' testing verify?
- That the material properties assigned to bone elements match published literature values
- That refining the mesh (increasing element count) no longer significantly changes the stress results (Correct answer)
- That boundary conditions applied at the bone-implant interface are physically realistic
- That the solver has correctly applied linear versus nonlinear material models
Correct answer: That refining the mesh (increasing element count) no longer significantly changes the stress results
Mesh convergence testing involves progressively refining the finite element mesh and comparing results; when further refinement produces negligible change in the stress or displacement solution, the mesh is considered converged and the results are reliable.
BE/B Eng Bachelor of Engineering Bachelor of Biomedical Engineering 5
Which principle governs the diffusion of oxygen from alveoli into pulmonary capillaries?