Q.1 What is the primary purpose of a bioreactor in tissue engineering?
To sterilize tissues
To grow cells
To analyze DNA
To measure temperature
Explanation - Bioreactors provide a controlled environment for cells or tissues to grow, allowing for the production of engineered tissues.
Correct answer is: To grow cells
Q.2 Which of the following is NOT a typical component of a bioreactor system?
Impeller
Culture medium
Microscope
Incubator
Explanation - While a microscope is used in cell analysis, it is not part of the core bioreactor hardware.
Correct answer is: Microscope
Q.3 In a bioreactor, what does 'agitation' refer to?
Mixing the culture medium
Changing the pH level
Heating the reactor
Adding nutrients
Explanation - Agitation ensures uniform distribution of oxygen, nutrients, and cells within the culture medium.
Correct answer is: Mixing the culture medium
Q.4 Which parameter is most directly affected by increasing the rotation speed of an impeller?
Temperature
Shear stress
Cell type
Medium color
Explanation - Higher rotation speeds increase the shear forces experienced by cells, influencing their behavior.
Correct answer is: Shear stress
Q.5 What does 'perfusion' mean in the context of a perfusion bioreactor?
Stirring the medium
Pumping fresh medium through the culture
Adding growth factors
Measuring pH
Explanation - Perfusion bioreactors continuously supply fresh medium and remove waste to support high-density cultures.
Correct answer is: Pumping fresh medium through the culture
Q.6 Which of the following best describes a 'static' culture system?
A system with continuous stirring
A system with no agitation
A system with automatic temperature control
A system that changes pH automatically
Explanation - Static cultures keep cells in a fixed position without mechanical mixing, often used for certain tissue types.
Correct answer is: A system with no agitation
Q.7 Why is oxygen solubility important in a bioreactor?
It determines cell color
It affects nutrient absorption
It is needed for cell respiration
It influences pH stability
Explanation - Oxygen is essential for cellular metabolism; inadequate oxygen can limit cell growth.
Correct answer is: It is needed for cell respiration
Q.8 What type of bioreactor is commonly used for 3D tissue constructs?
Stirred-tank bioreactor
Rotating wall vessel bioreactor
Batch bioreactor
Fermenter
Explanation - Rotating wall vessels provide a low-shear, microgravity-like environment suitable for 3D scaffold growth.
Correct answer is: Rotating wall vessel bioreactor
Q.9 Which parameter is typically monitored continuously during a bioreactor run?
Light intensity
pH
Humidity
Sound level
Explanation - pH can drift during culture and must be controlled to maintain cell viability.
Correct answer is: pH
Q.10 What is the main advantage of using a perfusion bioreactor over a batch bioreactor?
Lower cost
Higher shear stress
Continuous nutrient supply
Simpler design
Explanation - Perfusion systems maintain constant nutrient levels and waste removal, supporting higher cell densities.
Correct answer is: Continuous nutrient supply
Q.11 In tissue engineering, which of the following cells are commonly used for cartilage scaffold seeding?
Hepatocytes
Chondrocytes
Myocytes
Neurons
Explanation - Chondrocytes are the primary cells responsible for cartilage matrix production.
Correct answer is: Chondrocytes
Q.12 What does the term 'biomimicry' refer to in scaffold design?
Using synthetic polymers only
Replicating the natural extracellular matrix
Incorporating metal nanoparticles
Creating random structures
Explanation - Biomimicry involves designing scaffolds that emulate the mechanical and chemical properties of native tissue.
Correct answer is: Replicating the natural extracellular matrix
Q.13 Which of the following is a key consideration when scaling up a bioreactor from laboratory to clinical production?
Color of the medium
Sterility assurance level
Brand of impeller
Shape of the vessel
Explanation - Clinical-scale production requires stringent sterility to meet regulatory standards.
Correct answer is: Sterility assurance level
Q.14 What is 'shear-thinning' behavior in a polymer-based hydrogel?
Viscosity increases with shear
Viscosity decreases with shear
Viscosity stays constant
Viscosity depends on temperature
Explanation - Shear-thinning polymers become less viscous when stressed, facilitating cell encapsulation and injection.
Correct answer is: Viscosity decreases with shear
Q.15 Which of the following analytical techniques is commonly used to assess cell viability in a bioreactor?
PCR
Hemocytometer
Flow cytometry
Mass spectrometry
Explanation - Flow cytometry can differentiate live and dead cells using fluorescent dyes, allowing real-time viability analysis.
Correct answer is: Flow cytometry
Q.16 What is the function of a 'shear sensor' in a bioreactor?
Measure temperature
Detect mechanical stress
Monitor nutrient levels
Adjust pH
Explanation - Shear sensors provide feedback on the mechanical forces cells experience, crucial for sensitive cell types.
Correct answer is: Detect mechanical stress
Q.17 Which of the following best describes a 'continuous flow' bioreactor?
Medium is added and removed in batches
Medium is constantly pumped in and out
No medium is added
Medium is stirred but not replaced
Explanation - Continuous flow systems allow for steady-state cultures by maintaining constant media input and output.
Correct answer is: Medium is constantly pumped in and out
Q.18 Which parameter is most critical for controlling cell differentiation within a bioreactor?
Temperature
Electrical stimulation
Light exposure
Magnetic field intensity
Explanation - Electrical cues can direct stem cell lineage commitment, especially in electrically responsive tissues.
Correct answer is: Electrical stimulation
Q.19 What role does 'hydrogel porosity' play in nutrient diffusion?
Increases oxygen uptake
Blocks all diffusion
Reduces cell adhesion
Has no effect
Explanation - Higher porosity allows greater diffusion of oxygen and nutrients, improving cell survival in dense constructs.
Correct answer is: Increases oxygen uptake
Q.20 Which of the following is a typical method for sterilizing a bioreactor vessel?
UV radiation
Pasteurization
Gamma irradiation
All of the above
Explanation - UV, heat, and radiation methods are used to ensure sterility of bioreactor components.
Correct answer is: All of the above
Q.21 What is the purpose of 'bioreactor scaling laws'?
To determine the color of the vessel
To predict shear forces at larger volumes
To select the type of impeller
To measure pH
Explanation - Scaling laws help maintain comparable hydrodynamic conditions when increasing bioreactor size.
Correct answer is: To predict shear forces at larger volumes
Q.22 Which of the following cell types is NOT typically used in engineered skin constructs?
Keratinocytes
Fibroblasts
Adipocytes
Melanocytes
Explanation - While adipocytes are important in subcutaneous tissue, they are not commonly used in epidermal skin models.
Correct answer is: Adipocytes
Q.23 Why is 'pH control' essential during bioreactor operation?
To prevent corrosion
To maintain enzyme activity
To keep the vessel transparent
To reduce noise
Explanation - Enzymatic reactions in cells are pH-sensitive; deviations can impair metabolism and viability.
Correct answer is: To maintain enzyme activity
Q.24 What does 'oxygen transfer rate' (OTR) indicate?
Speed of medium mixing
Rate of oxygen movement into the culture
Rate of cell proliferation
Rate of pH change
Explanation - OTR quantifies how effectively oxygen is dissolved into the medium for cellular respiration.
Correct answer is: Rate of oxygen movement into the culture
Q.25 Which material is often used for bioreactor impeller blades to reduce corrosion?
Stainless steel
Aluminum
Copper
Nickel
Explanation - Stainless steel offers good corrosion resistance and is widely used in biomedical equipment.
Correct answer is: Stainless steel
Q.26 In a 'microcarrier' system, cells attach to:
Solid surfaces only
Microparticles suspended in medium
Glass slides
Air bubbles
Explanation - Microcarriers provide a large surface area for cells to attach and grow in stirred tanks.
Correct answer is: Microparticles suspended in medium
Q.27 Which of the following is a primary advantage of a 'scaffold-free' tissue engineering approach?
Simpler manufacturing
Lower mechanical strength
No need for biomaterials
Increased cell density
Explanation - Scaffold-free methods rely on cell-cell interactions, eliminating foreign scaffold materials.
Correct answer is: No need for biomaterials
Q.28 What is 'bioreactor washout'?
Loss of cells due to low nutrients
Excessive cleaning of the vessel
Removal of waste products
Removal of all cells from the reactor
Explanation - Washout occurs when cell density drops below a critical level, often due to nutrient depletion or excessive shear.
Correct answer is: Removal of all cells from the reactor
Q.29 Which of the following gases is most commonly used for sterilization of bioreactor components?
Oxygen
Nitrogen
Argon
Hydrogen peroxide vapor
Explanation - H2O2 vapor is effective for sterilizing complex equipment without heat damage.
Correct answer is: Hydrogen peroxide vapor
Q.30 What does a 'closed-loop' bioreactor system refer to?
No external input or output
Continuous input and output of medium
Only input but no output
Only output but no input
Explanation - Closed-loop systems maintain culture by exchanging medium while keeping the system sealed for sterility.
Correct answer is: Continuous input and output of medium
Q.31 Which parameter directly influences the shear stress experienced by cells in a stirred tank?
Impeller diameter
Medium viscosity
Temperature
Color of medium
Explanation - A larger impeller increases the fluid velocity, raising shear forces on cells.
Correct answer is: Impeller diameter
Q.32 What is the primary purpose of a 'bioreactor headspace'?
To store excess cells
To maintain temperature
To allow gas exchange
To hold stirring rods
Explanation - Headspace provides a volume for oxygen and CO2 to dissolve, maintaining gas balance.
Correct answer is: To allow gas exchange
Q.33 Which of the following is NOT a common cell line used in 3D bioreactor studies?
HeLa
HepG2
A549
E. coli
Explanation - E. coli is a bacterium and not used for mammalian tissue engineering in bioreactors.
Correct answer is: E. coli
Q.34 In a perfusion system, why is flow rate important?
It changes medium color
It controls nutrient delivery and shear stress
It adjusts pH
It affects medium taste
Explanation - Flow rate determines how fast fresh medium reaches cells and the shear forces they experience.
Correct answer is: It controls nutrient delivery and shear stress
Q.35 Which monitoring technique uses optical density to estimate cell concentration?
Spectrophotometry
Mass spectrometry
Chromatography
Electrophoresis
Explanation - Spectrophotometers measure light absorption at specific wavelengths, correlating with cell density.
Correct answer is: Spectrophotometry
Q.36 Which of the following is an advantage of a 'rotating wall vessel' over a stirred tank for stem cell cultures?
Higher shear stress
Microgravity-like environment
Simpler cleaning
Lower cost
Explanation - Rotating wall vessels reduce shear and simulate low-gravity conditions, benefiting delicate stem cells.
Correct answer is: Microgravity-like environment
Q.37 Which of the following materials is commonly used to fabricate 3D-printed scaffolds for bioreactors?
Polylactic acid (PLA)
Glass
Aluminum
Gold
Explanation - PLA is biodegradable and compatible with bioprinting, making it suitable for tissue scaffolds.
Correct answer is: Polylactic acid (PLA)
Q.38 What is the role of 'buffer systems' in bioreactor medium?
Maintain temperature
Regulate pH
Supply nutrients
Remove waste
Explanation - Buffers stabilize the medium's pH against metabolic changes during cell culture.
Correct answer is: Regulate pH
Q.39 Which of the following is a common challenge in scaling up bioreactor cultures?
Maintaining homogenous mixing
Changing color of medium
Increasing noise level
Decreasing oxygen levels automatically
Explanation - Scaling up often results in uneven mixing, leading to gradients that affect cell growth.
Correct answer is: Maintaining homogenous mixing
Q.40 What is 'cell aggregation' in a bioreactor context?
Cells sticking together forming clusters
Cells dividing rapidly
Cells losing adhesion to vessel walls
Cells being washed out
Explanation - Aggregation can lead to uneven distribution and affect nutrient diffusion within cultures.
Correct answer is: Cells sticking together forming clusters
Q.41 Which of the following is a key factor for maintaining 'shear-sensitive' cell populations?
High agitation speed
Low shear environments
High temperature
High light intensity
Explanation - Cells like stem cells or neurons are damaged by excessive shear; gentle conditions preserve them.
Correct answer is: Low shear environments
Q.42 Why is a 'temperature probe' used in a bioreactor?
To monitor cell metabolism
To adjust heating elements
To measure medium color
To sterilize the medium
Explanation - Temperature affects enzyme activity and cell growth; probes ensure it stays within the desired range.
Correct answer is: To monitor cell metabolism
Q.43 Which of the following is NOT a typical outcome of excessive shear in a bioreactor?
Cell death
Differentiation
Reduced proliferation
Enhanced aggregation
Explanation - High shear usually disperses aggregates and can kill cells; it does not promote aggregation.
Correct answer is: Enhanced aggregation
Q.44 What does 'hydraulic resistance' refer to in a perfusion bioreactor?
Resistance to blood flow
Resistance to medium flow due to scaffold pores
Resistance to heat transfer
Resistance to light absorption
Explanation - Pore size and scaffold density create resistance that affects perfusion efficiency.
Correct answer is: Resistance to medium flow due to scaffold pores
Q.45 Which of the following is a primary reason for using 'glucose monitoring' in bioreactor cultures?
To measure cell size
To assess metabolic activity
To control pH
To adjust oxygen levels
Explanation - Glucose consumption indicates cell metabolism; low levels signal the need for medium replenishment.
Correct answer is: To assess metabolic activity
Q.46 In a bioreactor, the 'mixing time' is the time required to:
Heat the medium
Stir the medium uniformly
Remove all waste
Change pH to neutral
Explanation - Mixing time measures how quickly the entire volume achieves homogeneity after stirring starts.
Correct answer is: Stir the medium uniformly
Q.47 Which of the following best describes a 'dual-phase' bioreactor?
Solid and liquid phase culture
Aerobic and anaerobic phase
Batch and perfusion phase
Cold and hot phase
Explanation - Dual-phase reactors support both cells on a scaffold (solid) and suspended in medium (liquid).
Correct answer is: Solid and liquid phase culture
Q.48 What is the typical range of oxygen tension (pO2) required for most mammalian cells in culture?
0-5 mmHg
20-40 mmHg
60-80 mmHg
90-110 mmHg
Explanation - Atmospheric oxygen (~21%) corresponds to ~20-40 mmHg; this range supports most cell types.
Correct answer is: 20-40 mmHg
Q.49 Which of the following is a typical cell density goal for 3D scaffold cultures?
10^4 cells/mL
10^6 cells/mL
10^8 cells/mL
10^10 cells/mL
Explanation - High densities (~10^6 cells/mL) are common for scaffold filling and tissue maturation.
Correct answer is: 10^6 cells/mL
Q.50 What is 'bioreactor inoculation'?
Adding bacteria to disinfect
Introducing initial cell population
Injecting oxygen
Adding nutrients
Explanation - Inoculation refers to seeding the culture vessel with the starting cell stock.
Correct answer is: Introducing initial cell population
Q.51 Which of the following is a key indicator of metabolic waste buildup in a bioreactor?
pH drop
Medium color change to yellow
Increased temperature
Reduced agitation speed
Explanation - Acidic metabolites lower pH; monitoring helps decide when to add fresh medium.
Correct answer is: pH drop
Q.52 In the context of bioreactor design, what does 'shear zone' refer to?
Area near the impeller with high shear
Area with no movement
Area with high temperature
Area with high light intensity
Explanation - The shear zone is the region where fluid velocities and shear forces are highest, affecting cell viability.
Correct answer is: Area near the impeller with high shear
Q.53 Which of the following is a typical 'end-point' analysis in a bioreactor experiment?
Measuring cell viability
Changing the reactor shape
Adding antibiotics
Adjusting light exposure
Explanation - End-point analyses assess culture health after a defined period, such as viability, proliferation, or differentiation markers.
Correct answer is: Measuring cell viability
Q.54 What is the primary advantage of using a 'parallel bioreactor array'?
Increased mixing speed
Multiple independent cultures for screening
Lower cost
Higher shear stress
Explanation - Arrays allow simultaneous testing of different conditions or cell lines.
Correct answer is: Multiple independent cultures for screening
Q.55 Which of the following is not typically a parameter controlled during bioreactor operation?
Temperature
Light intensity
pH
Oxygen tension
Explanation - While light can influence some cell types, most bioreactors do not control light unless culturing photoreactive cells.
Correct answer is: Light intensity
Q.56 What does a 'shear-thickening' polymer do under increased shear rates?
Viscosity decreases
Viscosity increases
Viscosity stays constant
It dissolves
Explanation - Shear-thickening materials become more viscous when stressed, which can protect cells from shear.
Correct answer is: Viscosity increases
Q.57 Which of the following is a commonly used sensor for monitoring dissolved oxygen?
Thermocouple
Optical oxygen sensor
pH meter
Conductivity probe
Explanation - Optical sensors measure oxygen levels by detecting changes in fluorescence or phosphorescence.
Correct answer is: Optical oxygen sensor
Q.58 In a bioreactor, what does 'medium turnover rate' describe?
Rate at which the medium changes temperature
Rate at which medium is replaced or refreshed
Rate at which cells are harvested
Rate at which pH is adjusted
Explanation - Turnover rate determines how often fresh nutrients are supplied and waste is removed.
Correct answer is: Rate at which medium is replaced or refreshed
Q.59 Which of the following is a primary function of 'scaffold porosity' in cell culture?
To increase cell adhesion
To prevent cell attachment
To reduce oxygen diffusion
To change color of medium
Explanation - Porosity provides space for cells to attach and migrate while allowing nutrient flow.
Correct answer is: To increase cell adhesion
Q.60 What is the main purpose of adding 'serum' to culture medium?
To provide nutrients and growth factors
To sterilize the medium
To change color
To increase pH
Explanation - Serum supplies essential proteins, hormones, and other factors that support cell growth.
Correct answer is: To provide nutrients and growth factors
Q.61 Which of the following is a typical cell type used in bone tissue engineering?
Osteoblasts
Erythrocytes
Neurons
Lymphocytes
Explanation - Osteoblasts are bone-forming cells essential for bone tissue constructs.
Correct answer is: Osteoblasts
Q.62 Which monitoring method measures CO2 levels in a bioreactor?
Optical sensor
Electrochemical sensor
Mass spectrometer
Thermocouple
Explanation - Electrochemical CO2 sensors detect the concentration of CO2 dissolved in the medium.
Correct answer is: Electrochemical sensor
Q.63 What does 'cell seeding density' refer to?
Number of cells per unit volume
Number of cells per unit mass of scaffold
Number of cells in the entire reactor
All of the above
Explanation - Seeding density describes the initial number of cells relative to volume, scaffold mass, or reactor capacity.
Correct answer is: All of the above
Q.64 Which of the following is an advantage of using a 'microfluidic' bioreactor?
Large culture volumes
Precise control of microenvironment
High shear stress
Complex geometry
Explanation - Microfluidic systems allow fine-tuning of flow, nutrient gradients, and mechanical cues at a small scale.
Correct answer is: Precise control of microenvironment
Q.65 Which of the following is a key consideration when selecting a bioreactor for vascular tissue engineering?
High shear stress to promote endothelial alignment
Low oxygen supply
Absence of perfusion
High temperature
Explanation - Endothelial cells align with flow; moderate shear improves vessel maturation.
Correct answer is: High shear stress to promote endothelial alignment
Q.66 What is the typical effect of increasing agitation speed on the oxygen transfer rate (OTR)?
Decrease OTR
Increase OTR
No effect
Reverse direction
Explanation - Higher agitation enhances mixing, promoting oxygen dissolution into the medium.
Correct answer is: Increase OTR
Q.67 Which parameter is NOT directly measured by a 'pH-stat' system?
pH
Buffer capacity
Nutrient concentration
Alkaline addition rate
Explanation - A pH-stat controls pH by adding base or acid; it does not directly monitor nutrients.
Correct answer is: Nutrient concentration
Q.68 Which of the following best describes a 'macro-scale' bioreactor?
Scales up from microfluidic to industrial volumes
Uses large impellers
Operates at cryogenic temperatures
Has a small volume (<1 mL)
Explanation - Macro-scale bioreactors refer to large-volume systems used in industrial production.
Correct answer is: Scales up from microfluidic to industrial volumes
Q.69 Which of the following is a commonly used cell line for bone marrow stromal cell cultures?
MSCs
HeLa
HepG2
C2C12
Explanation - Mesenchymal stem cells (MSCs) are derived from bone marrow and widely used for bone tissue engineering.
Correct answer is: MSCs
Q.70 What is a primary reason for adding 'extracellular matrix proteins' to a scaffold?
To increase scaffold stiffness
To promote cell attachment
To make scaffold opaque
To reduce nutrient diffusion
Explanation - ECM proteins like collagen or fibronectin enhance cell adhesion to synthetic scaffolds.
Correct answer is: To promote cell attachment
Q.71 In a perfusion bioreactor, what determines the optimal flow path through a scaffold?
Scaffold pore size and distribution
Color of the scaffold
Type of impeller
Ambient temperature
Explanation - The scaffold's geometry dictates how medium permeates, affecting nutrient delivery.
Correct answer is: Scaffold pore size and distribution
Q.72 Which of the following is a typical monitoring parameter for 'cell viability' using a live/dead assay?
Fluorescence intensity of calcein-AM
Temperature change
pH shift
Medium viscosity
Explanation - Calcein-AM stains live cells green; dead cells are counterstained with propidium iodide.
Correct answer is: Fluorescence intensity of calcein-AM
Q.73 Which of the following is a key benefit of using 'dynamic culture' over 'static culture' for 3D constructs?
Higher shear stress
Improved nutrient diffusion
Reduced cell proliferation
Simpler design
Explanation - Dynamic systems enhance transport of nutrients and waste, supporting thicker tissues.
Correct answer is: Improved nutrient diffusion
Q.74 What does 'bioreactor wall shear stress' primarily affect?
Cell alignment
Medium temperature
pH balance
Impeller speed
Explanation - Shear stress can orient cells along the flow direction, influencing tissue anisotropy.
Correct answer is: Cell alignment
Q.75 Which of the following is NOT a typical parameter adjusted to control a cell culture in a bioreactor?
Medium viscosity
Light exposure
Impeller speed
CO2 concentration
Explanation - Light is generally not a controlling parameter unless culturing photosensitive cells.
Correct answer is: Light exposure
Q.76 Which of the following is an advantage of using a 'single-use' bioreactor system?
Reduced risk of cross-contamination
Higher cost
Need for complex cleaning
Limited scalability
Explanation - Single-use systems eliminate the need for cleaning and sterilization, minimizing contamination.
Correct answer is: Reduced risk of cross-contamination
Q.77 What is 'cell seeding density' commonly expressed as?
cells/mL
cells/cm3
cells/g
All of the above
Explanation - Seeding density can be expressed per volume, per scaffold volume, or per scaffold mass.
Correct answer is: All of the above
Q.78 Which of the following is a potential consequence of inadequate medium agitation in a bioreactor?
Uneven nutrient distribution
Uniform cell growth
Higher oxygen transfer
Reduced shear stress
Explanation - Poor agitation creates gradients, leading to localized nutrient depletion.
Correct answer is: Uneven nutrient distribution
Q.79 Which parameter is most critical for maintaining cell viability during long-term bioreactor operation?
pH stability
Light intensity
Impeller color
Noise level
Explanation - Fluctuations in pH can drastically affect cell metabolism and survival.
Correct answer is: pH stability
Q.80 In a perfusion bioreactor, why is the 'flow path resistance' important?
It determines the color of the medium
It controls the rate of medium exchange
It has no effect
It changes the temperature
Explanation - Higher resistance slows flow, affecting nutrient delivery and waste removal.
Correct answer is: It controls the rate of medium exchange
Q.81 Which of the following is a characteristic of a 'microcarrier' in a stirred-tank bioreactor?
Large size (>1 mm)
Non-porous
Supports cell attachment
Requires static culture
Explanation - Microcarriers provide a large surface area for adherent cells in suspension culture.
Correct answer is: Supports cell attachment
Q.82 What is the main function of a 'pH-stat' in a bioreactor?
To maintain temperature
To adjust oxygen levels
To keep pH constant by adding acid/base
To stir the medium
Explanation - A pH-stat automatically adds acid or base to maintain desired pH during culture.
Correct answer is: To keep pH constant by adding acid/base
Q.83 Which of the following is a benefit of using a 'rotating wall vessel' for 3D cell culture?
High shear stress
Low oxygen transfer
Simulated microgravity environment
High temperature
Explanation - The low-shear environment promotes the formation of 3D spheroids.
Correct answer is: Simulated microgravity environment
Q.84 In a bioreactor, what is the purpose of using a 'temperature probe'?
To measure oxygen concentration
To measure medium temperature
To control pH
To monitor light exposure
Explanation - Temperature probes provide real-time data for maintaining optimal growth temperature.
Correct answer is: To measure medium temperature
Q.85 Which of the following best describes 'cell aggregation' in a bioreactor?
Cells attaching to the vessel walls
Cells forming clusters due to low shear
Cells being washed out
Cells dying
Explanation - Low shear conditions allow cells to cluster, which can affect nutrient diffusion.
Correct answer is: Cells forming clusters due to low shear
Q.86 Which of the following is a typical parameter monitored during a bioreactor run?
pH
Light intensity
Sound level
Wind speed
Explanation - pH is crucial for maintaining cell viability and metabolic activity.
Correct answer is: pH
Q.87 What does 'shear-thinning' mean for a polymer used in a scaffold?
Viscosity increases with shear
Viscosity decreases with shear
Viscosity stays constant
Viscosity is unaffected by temperature
Explanation - Shear-thinning polymers become less viscous under stress, aiding in cell encapsulation.
Correct answer is: Viscosity decreases with shear
Q.88 Which of the following is a key advantage of using a 'perfusion' bioreactor?
It requires no medium
It supports continuous nutrient supply
It eliminates the need for agitation
It reduces oxygen transfer
Explanation - Perfusion provides constant flow of fresh medium, maintaining nutrient levels and removing waste.
Correct answer is: It supports continuous nutrient supply
Q.89 What is the purpose of using 'microcarriers' in a stirred-tank bioreactor?
To increase mixing speed
To provide a surface for adherent cell growth
To decrease oxygen transfer
To add nutrients
Explanation - Microcarriers enlarge the available surface area for cells to attach in suspension culture.
Correct answer is: To provide a surface for adherent cell growth
Q.90 Which of the following is NOT typically a parameter controlled in a bioreactor?
Temperature
Shear stress
pH
Color of the medium
Explanation - Color is not a controllable parameter for cell culture conditions.
Correct answer is: Color of the medium
Q.91 Which type of bioreactor is best suited for scaling up the production of engineered cartilage?
Stirred-tank bioreactor
Static culture chamber
Rotating wall vessel
Centrifuge
Explanation - The low-shear environment of rotating wall vessels supports the growth of cartilage cells in 3D constructs.
Correct answer is: Rotating wall vessel
Q.92 What is a common method to monitor cell density in a bioreactor?
Spectrophotometry
pH meter
Thermocouple
Light meter
Explanation - Spectrophotometry measures absorbance of light at specific wavelengths, correlating with cell concentration.
Correct answer is: Spectrophotometry
Q.93 Which parameter directly influences the shear stress experienced by cells in a stirred-tank bioreactor?
Impeller speed
Medium color
Ambient light intensity
Vessel shape
Explanation - Higher impeller speeds increase fluid velocity and shear forces on cells.
Correct answer is: Impeller speed
Q.94 Which of the following is a common cell type used in skin tissue engineering?
Keratinocytes
Neurons
Cardiomyocytes
Adipocytes
Explanation - Keratinocytes form the outer layer of skin and are key for engineered epidermal constructs.
Correct answer is: Keratinocytes
Q.95 What is the main function of a 'buffer system' in cell culture medium?
Maintain temperature
Maintain pH
Provide nutrients
Prevent contamination
Explanation - Buffers stabilize the medium’s pH against metabolic changes during culture.
Correct answer is: Maintain pH
Q.96 Which of the following is a key advantage of a 'perfusion bioreactor' over a batch system?
Lower oxygen transfer
Continuous nutrient supply
Higher shear stress
Simpler operation
Explanation - Perfusion maintains constant nutrient levels and waste removal, enabling higher cell densities.
Correct answer is: Continuous nutrient supply
Q.97 Which of the following is a typical cell density used for 3D scaffold culture?
1×10^5 cells/mL
1×10^6 cells/mL
1×10^7 cells/mL
1×10^8 cells/mL
Explanation - A density around 10^6 cells/mL is common for filling scaffolds with cells.
Correct answer is: 1×10^6 cells/mL
Q.98 What is the purpose of a 'shear sensor' in a bioreactor?
Measure temperature
Detect shear forces
Monitor pH
Track medium color
Explanation - Shear sensors provide feedback on mechanical forces experienced by cells.
Correct answer is: Detect shear forces
Q.99 What does the term 'hydraulic resistance' refer to in a perfusion bioreactor?
Resistance to heat transfer
Resistance to medium flow through the scaffold
Resistance to oxygen diffusion
Resistance to light absorption
Explanation - The scaffold’s pore size and density create resistance that affects perfusion efficiency.
Correct answer is: Resistance to medium flow through the scaffold
Q.100 Which of the following is a typical parameter that is monitored in a bioreactor?
pH
Wind speed
Light intensity
Ambient noise level
Explanation - pH is critical for cell viability and metabolic activity.
Correct answer is: pH
Q.101 Which of the following is a typical cell type used in bone tissue engineering?
Osteoblasts
Erythrocytes
Neurons
Lymphocytes
Explanation - Osteoblasts are bone-forming cells essential for bone tissue constructs.
Correct answer is: Osteoblasts
Q.102 Which monitoring method is commonly used to measure dissolved oxygen in a bioreactor?
Optical sensor
Thermocouple
pH meter
Light meter
Explanation - Optical sensors detect oxygen levels by changes in fluorescence or phosphorescence.
Correct answer is: Optical sensor
Q.103 What is the main advantage of a 'rotating wall vessel' bioreactor for stem cell cultures?
High shear stress
Microgravity-like environment
Simpler cleaning
Higher temperature
Explanation - The low-shear environment reduces stress on sensitive stem cells, supporting their proliferation.
Correct answer is: Microgravity-like environment
Q.104 Which of the following materials is commonly used for 3D-printed scaffolds in bioreactors?
Polylactic acid (PLA)
Glass
Aluminum
Gold
Explanation - PLA is biodegradable and compatible with bioprinting for tissue scaffolds.
Correct answer is: Polylactic acid (PLA)
Q.105 In a perfusion system, why is flow rate important?
It controls nutrient delivery and shear stress
It changes medium color
It adjusts pH
It affects medium taste
Explanation - Flow rate determines how fast fresh medium reaches cells and the shear forces they experience.
Correct answer is: It controls nutrient delivery and shear stress
Q.106 Which of the following is a typical cell type used in vascular tissue engineering?
Endothelial cells
Neurons
Cardiomyocytes
Adipocytes
Explanation - Endothelial cells line blood vessels and are crucial for engineered vascular grafts.
Correct answer is: Endothelial cells
Q.107 Which of the following is not typically used as a perfusion bioreactor medium component?
Glucose
Fetal bovine serum
Bacterial lysate
Hydroxyapatite
Explanation - Hydroxyapatite is a scaffold material, not a medium component.
Correct answer is: Hydroxyapatite
Q.108 Which of the following best describes a 'dual-phase' bioreactor?
Solid and liquid phase culture
Batch and perfusion phase
Aerobic and anaerobic phase
Static and dynamic phase
Explanation - Dual-phase reactors support both cells on a scaffold (solid) and suspended in medium (liquid).
Correct answer is: Solid and liquid phase culture
Q.109 Which of the following is a key factor in maintaining cell viability in long-term bioreactor culture?
Stable pH
High noise level
Constant light
Low temperature
Explanation - Fluctuating pH can disrupt cellular metabolism and viability.
Correct answer is: Stable pH
Q.110 In a bioreactor, which of the following is a common method to assess cell viability?
Live/Dead assay
Color change
Sound level measurement
Temperature reading
Explanation - Live/Dead assays use fluorescent dyes to differentiate viable from non-viable cells.
Correct answer is: Live/Dead assay
Q.111 Which of the following best explains the concept of 'oxygen transfer rate' (OTR) in a bioreactor?
The rate at which oxygen is consumed by cells
The rate at which oxygen dissolves into the medium
The rate of temperature change
The rate of light absorption
Explanation - OTR quantifies how effectively oxygen is transferred from gas to liquid phase for cell use.
Correct answer is: The rate at which oxygen dissolves into the medium
Q.112 Which of the following is a major challenge when scaling up bioreactors from lab to industrial scale?
Maintaining homogenous mixing
Changing the color of the medium
Increasing the noise level
Reducing oxygen levels automatically
Explanation - Larger volumes can create mixing gradients, affecting cell growth and product consistency.
Correct answer is: Maintaining homogenous mixing
Q.113 Which of the following is a typical monitoring parameter for 'cell viability' using a live/dead assay?
Fluorescence intensity of calcein-AM
Temperature change
pH shift
Medium viscosity
Explanation - Calcein-AM stains live cells green; dead cells are counterstained with propidium iodide.
Correct answer is: Fluorescence intensity of calcein-AM
Q.114 Which of the following is NOT a typical parameter controlled in a bioreactor?
Medium viscosity
Light exposure
Impeller speed
CO2 concentration
Explanation - Light is generally not a controlling parameter unless culturing photosensitive cells.
Correct answer is: Light exposure
Q.115 Which of the following is an advantage of a 'single-use' bioreactor system?
Reduced risk of cross-contamination
Higher cost
Need for complex cleaning
Limited scalability
Explanation - Single-use systems eliminate the need for cleaning and sterilization, minimizing contamination.
Correct answer is: Reduced risk of cross-contamination
Q.116 Which of the following is a typical cell density goal for 3D scaffold cultures?
10^4 cells/mL
10^6 cells/mL
10^8 cells/mL
10^10 cells/mL
Explanation - High densities (~10^6 cells/mL) are common for scaffold filling and tissue maturation.
Correct answer is: 10^6 cells/mL
Q.117 Which of the following is a key advantage of using a 'microfluidic' bioreactor?
Large culture volumes
Precise control of microenvironment
High shear stress
Complex geometry
Explanation - Microfluidic systems allow fine-tuning of flow, nutrient gradients, and mechanical cues at a small scale.
Correct answer is: Precise control of microenvironment
Q.118 Which of the following is a typical cell type used in cartilage tissue engineering?
Chondrocytes
Fibroblasts
Adipocytes
Melanocytes
Explanation - Chondrocytes produce cartilage matrix and are essential for engineered cartilage constructs.
Correct answer is: Chondrocytes
Q.119 Which of the following is an important factor for maintaining cell viability in a perfusion bioreactor?
Shear stress level
Medium viscosity
Temperature
All of the above
Explanation - Shear, viscosity, and temperature all influence cell survival and metabolism in perfusion cultures.
Correct answer is: All of the above
Q.120 What is the main function of a 'pH-stat' in a bioreactor?
To maintain temperature
To adjust oxygen levels
To keep pH constant by adding acid/base
To stir the medium
Explanation - A pH-stat automatically adds acid or base to maintain desired pH during culture.
Correct answer is: To keep pH constant by adding acid/base
Q.121 Which of the following is a typical cell type used in bone marrow stromal cell cultures?
MSCs
HeLa
HepG2
C2C12
Explanation - Mesenchymal stem cells (MSCs) are derived from bone marrow and widely used for bone tissue engineering.
Correct answer is: MSCs
Q.122 In a bioreactor, what does the term 'mixing time' refer to?
Time to heat the medium
Time to stir uniformly
Time to remove all waste
Time to adjust pH to neutral
Explanation - Mixing time measures how quickly the entire volume achieves homogeneity after stirring starts.
Correct answer is: Time to stir uniformly
Q.123 Which of the following is a typical monitoring parameter for a bioreactor?
pH
Wind speed
Light intensity
Ambient noise level
Explanation - pH is critical for maintaining cell viability and metabolic activity.
Correct answer is: pH
Q.124 Which of the following best describes 'shear-thickening' polymer behavior?
Viscosity decreases with shear
Viscosity increases with shear
Viscosity stays constant
Viscosity is unaffected by temperature
Explanation - Shear-thickening materials become more viscous under stress, which can protect cells from shear.
Correct answer is: Viscosity increases with shear
Q.125 What is the main advantage of a 'rotating wall vessel' for 3D cell culture?
High shear stress
Low oxygen transfer
Simulated microgravity environment
High temperature
Explanation - The low-shear environment promotes the formation of 3D spheroids.
Correct answer is: Simulated microgravity environment
Q.126 Which of the following is a typical cell type used for vascular tissue engineering?
Endothelial cells
Neurons
Cardiomyocytes
Adipocytes
Explanation - Endothelial cells line blood vessels and are crucial for engineered vascular grafts.
Correct answer is: Endothelial cells
Q.127 What does a 'hydraulic resistance' value indicate in a perfusion bioreactor?
Resistance to temperature change
Resistance to medium flow through the scaffold
Resistance to oxygen diffusion
Resistance to light absorption
Explanation - The scaffold’s pore size and density create resistance that affects perfusion efficiency.
Correct answer is: Resistance to medium flow through the scaffold
Q.128 Which of the following is a key factor for maintaining cell viability in a perfusion bioreactor?
Shear stress level
Medium viscosity
Temperature
All of the above
Explanation - Shear, viscosity, and temperature all influence cell survival and metabolism in perfusion cultures.
Correct answer is: All of the above
Q.129 Which of the following is a typical monitoring parameter for 'cell viability' using a live/dead assay?
Fluorescence intensity of calcein-AM
Temperature change
pH shift
Medium viscosity
Explanation - Calcein-AM stains live cells green; dead cells are counterstained with propidium iodide.
Correct answer is: Fluorescence intensity of calcein-AM
Q.130 What does the term 'bioreactor scale-up' primarily refer to?
Increasing vessel size for larger cell production
Reducing temperature
Changing the color of the medium
Adding more nutrients
Explanation - Scale-up involves moving from small laboratory reactors to larger production-scale vessels.
Correct answer is: Increasing vessel size for larger cell production
Q.131 Which of the following is an advantage of a 'microcarrier' in a stirred-tank bioreactor?
Increases mixing speed
Provides surface for adherent cell growth
Decreases oxygen transfer
Adds nutrients
Explanation - Microcarriers enlarge the available surface area for cells to attach in suspension culture.
Correct answer is: Provides surface for adherent cell growth
Q.132 Which parameter directly influences the shear stress experienced by cells in a stirred-tank bioreactor?
Impeller speed
Medium color
Ambient light intensity
Vessel shape
Explanation - Higher impeller speeds increase fluid velocity and shear forces on cells.
Correct answer is: Impeller speed
Q.133 Which of the following is a typical monitoring parameter for a bioreactor?
pH
Wind speed
Light intensity
Ambient noise level
Explanation - pH is critical for maintaining cell viability and metabolic activity.
Correct answer is: pH