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Multiple choice question for engineering

Set 1

1. Primary plant cells are better formed aggregates than animal cells.
a) True
b) False

View Answer

Answer: a [Reason:] Unlike plant cells, primary mammalian cells do not normally form aggregates, but grow in the form of monolayers on support surfaces such as glass surfaces of flasks. Using the proteolytic enzyme trypsin, individual cells in a tissue can be separated to form single-cell cultures.

2. What does “T” refers to in Tissue culture flask (T-Flask)?
a) Total volume of the flask
b) Total weight of the flask
c) Total surface area of the flask
d) Total mass of the flask

View Answer

Answer: c [Reason:] The “T” referred to the total surface area of the flask that was available for cell growth: thus a T-25 flask had a 25cm2 growth area. By the 1960s, straight neck T-flasks was available molded from polystyrene that was treated to enhance cell attachment.

3. Which of the following is not a type of basic T-Flask?
a) T-25
b) T-55
c) T-75
d) T-175

View Answer

Answer: b [Reason:] Flasks are divided into 6 types, depending on the culture scale and the cap type. Cell growth area for T25, T75 and T175 are 25 cm², 75 cm², and 175 cm², respectively. Each flask can be provided with plug or filter caps.

4. EDTA is carcinogenic.
a) True
b) False

View Answer

Answer: b [Reason:] The typical concentration of use of EDTA is less than 2%, with the other salts in current use at even lower concentrations. The lowest dose reported to cause a toxic effect in animals was 750 mg/kg/day. These chelating agents are cytotoxic and weakly genotoxic, but not carcinogenic.

5. Transformed cell lines are immortal.
a) True
b) False

View Answer

Answer: a [Reason:] Cells that can be propagated indefinitely are called continuous, immortal, or transformed cell lines. Cancer cells are naturally immortal. All cancerous cell lines are transformed, although it is not clear whether all transformed cell lines are cancerous.

6. Nontransformed cell lines form monolayer whereas transformed cell lines form multilayer.
a) True
b) False

View Answer

Answer: a [Reason:] One particular characteristic is contact inhibition. In two-dimensional culture on a surface nontransformed cells form only a monolayer, as cell division is inhibited when a cell’s surface is in contact with other cells. Transformed cells do not “sense” the presence of other cells and keep on dividing to form multilayer structures.

7. Baculovirus infects insect cell lines and are also pathogenic to humans.
a) True
b) False

View Answer

Answer: b [Reason:] The baculovirus that infects insect cells is an ideal vector for genetic engineering, because it is nonpathogenic to humans and has a very strong promoter that encodes for a protein that is not essential for virus production in cell culture. The insertion of a gene under the control of this promoter can lead to high expression levels (40% of the total protein as the target protein).

8. Hybridoma cells have an application to produce:
a) Antigens
b) Antibodies
c) Cancer cells
d) Cell lines

View Answer

Answer: b [Reason:] Hybridoma cells are obtained by fusing lymphocytes (normal blood cells that make antibodies) with myeloma (cancer) cells. Lymphocytes producing antibodies grow slowly and are mortal. After fusion with myeloma cells, hybridomas become immortal, can reproduce indefinitely, and produce antibodies. Using hybridoma cells, highly specific, monoclonal (originating from one cell) antibodies can be produced against specific antigens.

9. Vaccine is not a serum.
a) True
b) False

View Answer

Answer: a [Reason:] Both antisera and antitoxins are means of proactively combating infections. The introduction of compounds to which the immune system responds is an attempt to build up protection against microorganisms or their toxins before the microbes actually invade the body.

10. Serum does not require sterilization.
a) True
b) False

View Answer

Answer: b [Reason:] Serum must be filtered sterilized, and contamination with viruses and possibly mycoplasma (a wall less bacterium) are potential problems. Contamination by prions (agents that cause diseases such as “mad cow” disease) is a real concern, and source animals cannot come from regions known to have contaminated animals.

11. What is the full form of MEM in Eagle’s cell culture medium?
a) Maximum evaporating medium
b) Maximum essential medium
c) Minimum essential medium
d) Minimum evaporating medium

View Answer

Answer: c [Reason:] Eagle’s minimal essential medium (EMEM) is a cell culture medium developed by Harry Eagle that can be used to maintain cells in tissue culture.

12. Transferrin is present in serum media.
a) True
b) False

View Answer

Answer: b [Reason:] A simpler serum-free medium may contain insulin, transferrin, and selenium as serum replacement components, in addition to glucose, glutamine, other amino acids, and salts.

13. Small bubbles are more shear sensitive than large bubbles.
a) True
b) False

View Answer

Answer: b [Reason:] Animal cells are very shear sensitive, and rising air bubbles may cause shear damage to cells, particularly at the point of bubble rupture. Very small bubbles are less damaging.

14. Pluronic F-68 is ____________
a) Ionic
b) Non-ionic
c) Covalent
d) Metallic

View Answer

Answer: b [Reason:] Poloxamers are nonionic triblock copolymers composed of a central hydrophobic chain of polyoxypropylene (poly(propylene oxide)) flanked by two hydrophilic chains of polyoxyethylene (poly(ethylene oxide)). Poloxamers are also known by the trade names Synperonics, Pluronics, and Kolliphor.

15. Spinner flask contains:
a) Spindle shaped agitators
b) Cylindrical agitators
c) Simple agitators
d) Spoon-like agitators

View Answer

Answer: d [Reason:] Spinner flasks contain a magnetically driven impeller or spoonlike agitators that operate at 10 to 60 rpm. Aeration is usually by surface aeration using 5% CO2-enriched and filtered air for mammalian cell lines. Spinner flasks are set on a magnetic stirrer plate in a CO2 incubator.

Set 2

1.” Chemical reactions or phase changes occur” is this statement applicable for unsteady state energy balance?
a) True
b) False

View Answer

Answer: b [Reason:] No chemical reactions or phase changes occur as the system is well mixed with uniform temperature and composition. Properties of the outlet stream are therefore the same as within the system and mixtures and solutions are ideal.

2. A boat has a thermo-server attached to it. While floating with the fluid, it measures the temperature of the fluid. Both flow and temperature are under unsteady-state condition:
T ( x, y, z, t) = x2 + yz + t
(V ) ⃗ (x, y, z, t) = 2xi + 2 t2 yj ̂ + k ̂
Determine the rate of change of the temperature recorded by the sensor at t = 1, when the boat flows past the location, whose spatial co-ordinates are 2i + j + k.
bioprocess-engineering-questions-answers-aptitude-test-q2
Here, (x, y, z) = (2, 1, 1)
a) 30
b) 25
c) 20
d) 35

View Answer

Answer: c [Reason:] Substituting in the equation given in the question: bioprocess-engineering-questions-answers-solving-unsteady-state-energy-balances-q2-exp

3. The exothermic elementary liquid-phase reaction is as below:

bioprocess-engineering-questions-answers-solving-unsteady-state-energy-balances-q3

is carried out in a batch reactor with a cooling coil to keep the reactor isothermal at 27◦C. The reactor is initially charged with equal concentrations of A and B and no C, cAo = cBo = 2.0 mol/L, cCo = 0.
Additional data:
Rate constant, k = 0.01725 L/mol . min, at 27°C
Heat of reaction, ΔHR = -10 kcal/mol A, at 27°C
Partial molar heat capacities, C ̅PA = C ̅PB = 20 cal/mol . K, C ̅PC = 40 cal/mol K
Reactor volume, VR = 1200 L
How long does it take to reach 95% conversion?
a) 550 min
b) 552 min
c) 553 min
d) 551 min

View Answer

Answer: d [Reason:] Assuming constant density, the material balance for component A is bioprocess-engineering-questions-answers-solving-unsteady-state-energy-balances-q3-a

The stoichiometry of the reaction, and the material balance for B gives bioprocess-engineering-questions-answers-solving-unsteady-state-energy-balances-q3-b

or cA = cB. Substitution into the material balance for species A gives

bioprocess-engineering-questions-answers-solving-unsteady-state-energy-balances-q3-c-1

Separation of variables and integration gives

bioprocess-engineering-questions-answers-solving-unsteady-state-energy-balances-q3-d

Substituting cA= 0.05cAo and the values for k and cAo gives

t = 551 min.

4. Refer to Q3, and estimate what is the total amount of heat (kcal) that must be removed by the cooling coil when this conversion is reached?
Using the following equation:
Q ̇ = ΔHR r VR
a) -2.3 × 104 kcal
b) -2.2 × 104 kcal
c) -2.4 × 104> kcal
d) -2.6 × 104 kcal

View Answer

Answer: a [Reason:] We assume the incompressible-fluid energy balance is accurate for this liquidphase reactor. If the heat removal is manipulated to maintain constant reactor temperature, the time derivative in Equation vanishes leaving Q ̇ = ΔHR r VR Substituting dcA/ dt = -r and multiplying through by dt gives dQ = – ΔHR VR dcA Integrating both sides gives Q = – ΔHR VR (cA- cAO) = -2.3 × 104 kcal.

5. Refer to Q3 and Q4 and estimate what is the maximum rate at which heat must be removed by the cooling coil (kcal/min) and at what time does this maximum occur?
Using the following equation:
Q ̇ = ΔHR kc2Ao VR
a) −828 kcal/min
b) –880 kcal/min
c) -825 kcal/min
d) – 850 kcal/min

View Answer

Answer: a [Reason:] The right-hand side is a maximum in absolute value (note it is a negative quantity) when cA is a maximum, which occurs for cA = cAo, giving

Qmax = ΔHR kc2Ao VR = (−10 kcal/mol A) (0.01725 L/mol•min ) (2.0 mol/L )2 (1200 L ) = −828 kcal/min.

6. Refer to Q3, Q4 and Q5 estimate what is the adiabatic temperature rise for this reactor and what is its significance?
Using the equation:
bioprocess-engineering-questions-answers-solving-unsteady-state-energy-balances-q6
a) 230 K
b) 200 K
c) 250 K
d) 260 K

View Answer

Answer: c [Reason:] The maximum temperature rise corresponds to complete conversion of the reactants and can be computed from the given data

bioprocess-engineering-questions-answers-solving-unsteady-state-energy-balances-q7

The adiabatic temperature rise indicates the potential danger of a coolant system failure. In this case the reactants contain enough internal energy to raise the reactor temperature by 250 K.

7.” All of the coolant is at a uniform temperature, Tc”, is this statement correct according to the assumptions for the Unsteady-state energy balance?
a) True
b) False

View Answer

Answer: a [Reason:] All of the coolant is at a uniform temperature, Tc as the increase in coolant temperature as the coolant passes through the coil is neglected.

8. Fruit juice is fed to a heat exchanges at the rate of 15 kg/h. Saturated steam at 145 kPa pressure is used to heat the juice from 70C to 900C. Assuming the heat capacity of juice 5kJ/kg0C, find out the quantity of steam required for the operation.
bioprocess-engineering-questions-answers-solving-unsteady-state-energy-balances-q8

Using the equation:
FHF + SHS = PHP + CHC
λs (Latent heat of condensation) = 2229 at 145 kPa.
a) 2.90 kg/h
b) 2.97 kg/h
c) 2.99 kg/h
d) 2.95 kg/h

View Answer

Answer: b [Reason:] Equation given in the question can be rewritten as : bioprocess-engineering-questions-answers-solving-unsteady-state-energy-balances-q8-1 The negative sign indicates the heat is given from the steam to juice. Hence, the amount of steam required is 2.97 kg/h for raising the temperature of 15 kg/h fruit juice from 7°C to 900°C.

9. The evaporator economy is dependent on the ________
a) Heat transfer rate
b) Mass transfer rate
c) Energy balance considerations
d) Mass balance considerations

View Answer

Answer: a [Reason:] There are three main measures of evaporator performance: Capacity (kg vaporized/ time), Economy (kg vaporized/ kg steam input), Steam consumption (kg/hr). The performance of a evaporator is evaluated by the capacity and the economy. The rate of heat transfer q through the heating surface of an evaporator, by the definition of overall heat transfer coefficient, is product of three factors i) The area of heat transfer surface A ii) The overall heat transfer coefficient U iii) The overall temperature drop ΔT

Q = U * A * ΔT.

10. The fouling factor is _________
a) Is a safety factor
b) Accounts for all resistances due to mass transfer
c) Is a dimensionless number
d) Accounts for all resistances due to heat transfer

View Answer

Answer: d [Reason:] The fouling factor represents the theoretical resistance to heat flow due to a build-up of a layer of dirt or other fouling substance on the tube surfaces of the heat exchanger, but they are often overstated by the end user in an attempt to minimise the frequency of cleaning. In reality, if the wrong fouling factor is used, cleaning may actually be required more frequently.

11. The units for the log mean temperature difference are __________
a) 1/ °C
b) °C
c) ½ °C
d) Dimensionless

View Answer

Answer: b [Reason:] In the particular system, whatever unit is assigned to temperature, the same is the unit of LMTD. It is just a special kind of temperature difference. Logarithmic mean temperature difference. LMTD is a logarithmic average of the temperature difference between the hot and cold streams in heat exchanger. Its unit is whatever is the unit of the temperature. °F or °C or Kelvin.

Set 3

1. In tissue culture media which ions inhibit trypsin from the following?
a) Na+
b) Pb2+
c) Mg2+
d) Fe2+

View Answer

Answer: c [Reason:] Tissue culture media contains calcium and magnesium ions, fetal bovine serum contains proteins that are trypsin inhibitors. Both Mg2+ and Ca2+ inhibit trypsin. To weaken the function of adhesion molecules.

2. EDTA function as_________
a) Divalent cations chelator
b) Divalent anion chelator
c) Monovalent cation chelator
d) Monovalent anion chelator

View Answer

Answer: a [Reason:] EDTA is frequently included in the trypsin solution for its function as divalent cations chelator.

3. EDTA is carcinogenic.
a) True
b) False

View Answer

Answer: b [Reason:] The typical concentration of use of EDTA is less than 2%, with the other salts in current use at even lower concentrations. The lowest dose reported to cause a toxic effect in animals was 750 mg/kg/day. These chelating agents are cytotoxic and weakly genotoxic, but not carcinogenic.

4. Spinner flask contains:
a) Spindle shaped agitators
b) Cylindrical agitators
c) Simple agitators
d) Spoon-like agitators

View Answer

Answer: d [Reason:] Spinner flasks contain a magnetically driven impeller or spoonlike agitators that operate at 10 to 60 rpm. Aeration is usually by surface aeration using 5% CO2-enriched and filtered air for mammalian cell lines. Spinner flasks are set on a magnetic stirrer plate in a CO2 incubator.

5. What do you mean by microcarrier?
a) Carrier of small molecules
b) Carrier of small cells
c) Support material of suspended cells
d) Support material of adherent cells

View Answer

Answer: d [Reason:] A microcarrier is a support matrix allowing for the growth of adherent cells in bioreactors. Microcarriers are regularly used to grow protein-producing or virus-generating adherent cell populations in the large-scale commercial production of biologics (proteins) and vaccines.

6. Membrane bioreactor is the combination of microfiltration and ultrafiltration.
a) True
b) False

View Answer

Answer: a [Reason:] Membrane bioreactor (MBR) is the combination of a membrane process like microfiltration or ultrafiltration with a biological wastewater treatment process, the activated sludge process. It is now widely used for municipal and industrial wastewater treatment.

7. In microencapsulation which of the coating materials is not used for coating:
a) Sodium alginate
b) Sodium chloride
c) Gelatin
d) Polyvinyl alcohol

View Answer

Answer: b [Reason:] The coating materials generally used for coating are: ▪ Ethyl cellulose ▪ Polyvinyl alcohol ▪ Gelatin ▪ Sodium alginate The definition has been expanded, and includes most foods, where the encapsulation of flavors is the most common. The technique of microencapsulation depends on the physical and chemical properties of the material to be encapsulated.

8. What do you mean by spent medium?
a) Medium with high nutritional content
b) Hydrated
c) Dehydrated
d) Non-toxic

View Answer

Answer: c [Reason:] After each sub-culture, the medium is discarded because it has been depleted of nutrients, dehydrated or accumulated toxic metabolic products.

9. In relation to surface area roller bottles are less advantageous than T-Flask.
a) True
b) False

View Answer

Answer: b [Reason:] The roller-bottle system has an advantage over T-flasks because of increased surface area, agitation of the liquid, and better aeration. Roller bottles are not typically used for large-scale production because of high labor requirements and bottle-to-bottle variability.

10. DEAE beads are negatively charged.
a) True
b) False

View Answer

Answer: b [Reason:] Anion-exchange chromatography is a process that separates substances based on their charges using an ion-exchange resin containing positively charged groups, such as diethyl-aminoethyl groups (DEAE). In solution, the resin is coated with positively charged counter-ions (cations).

11. Hydrofoils give low turbulence.
a) True
b) False

View Answer

Answer: a [Reason:] Propellers (marine or hydrofoil) give an inlet and outlet which are on axial direction, preferably downward, they are characterized by a nice pumping flow, low energy consumption and low shear magnitude as well as low turbulence.

12. The cells are prone to damage at which region?
a) Inside the gas bubble
b) Outside the medium
c) Interface of a gas bubble and medium
d) Inside the medium

View Answer

Answer: c [Reason:] Only cells that are at the interface of an eddy and another eddy or another surface (e.g., reactor wall) are likely to experience damage. Cells at the gas–liquid interface are particularly prone to damage. The breakage of air bubbles is particularly destructive to cells that accumulate at the interface of a gas bubble and medium.

13. Pluronic F-68 is____________
a) Ionic
b) Non-ionic
c) Covalent
d) Metallic

View Answer

Answer: b [Reason:] Poloxamers are nonionic triblock copolymers composed of a central hydrophobic chain of polyoxypropylene (poly(propylene oxide)) flanked by two hydrophilic chains of polyoxyethylene (poly(ethylene oxide)). Poloxamers are also known by the trade names Synperonics, Pluronics, and Kolliphor.

14. The accumulation of toxic metabolic products in beads is a problem of which of the following methods?
a) Gel beads
b) Microencapsulation
c) Tubular ceramic matrix
d) Roller bottles

View Answer

Answer: a [Reason:] High cell densities make high volumetric productivities possible. However, the control of microenvironmental conditions inside bead particles and the accumulation of toxic metabolic products in beads are potential problems in the immobilization of mammalian cells in gel beads (agar, alginate, collagen, polyacrylamide).

15. Small bubbles are more shear sensitive than large bubbles.
a) True
b) False

View Answer

Answer: b [Reason:] Animal cells are very shear sensitive, and rising air bubbles may cause shear damage to cells, particularly at the point of bubble rupture. Very small bubbles are less damaging.

Set 4

1. The centrifugation is based on the principle of when a force is less than the gravity desired.
Is the statement true or false?
a) True
b) False

View Answer

Answer: b [Reason:] The “fictitious” force on everything that points opposite that of gravity, the effect of gravity is reduced. Many particles or cells in a liquid suspension, given time, will eventually settle at the bottom of a container due to gravity. However the length of time required for such separations is impractical. Other particles, extremely small in size, will not separate at all in solution, unless subjected to high centrifugal force.

2. In 500 × g, what does g represent in accordance to centrifugation?
a) Gravitational force
b) Centrifugal force is 500 times greater than earthly gravitational force
c) Centrifugal force is 500 times less than earthly gravitational force
d) Centrifugal force is 500 times same as that of earthly gravitational force

View Answer

Answer: b [Reason:] Centrifuge is any device that applies a sustained centrifugal force; that is, a force due to rotation. Effectively, the centrifuge substitutes a similar, stronger, force for that of gravity. When a suspension is rotated at a certain speed or revolutions per minute (RPM), centrifugal force causes the particles to move radially away from the axis of rotation. The force on the particles (compared to gravity) is called Relative Centrifugal Force (RCF). For example, an RCF of 500 x g indicates that the centrifugal force is 500 times greater than earthly gravitational force.

3. Which of the following is not a type of centrifugation?
a) Hydro cyclone
b) Tubular centrifuge
c) Microfiltration
d) Disk stack separator

View Answer

Answer: c [Reason:] Microfiltration is a membrane filtration process which removes contaminants from a fluid by microporous membrane. The membrane pore size ranges from 0.1 to 10 micrometers. Microfiltration is different from reverse osmosis and nanofiltration because it does not require pressure and does not remove dissolved contaminants. However, centrifugation is often effective when the particles are very small and difficult to filter.

4. By increasing the feed rate of the liquid in tubular centrifuge the performance is increased?
a) True
b) False

View Answer

Answer: b [Reason:] As the feed rate is increased the liquid layer moving up the wall of the centrifuge becomes thicker; this reduces performance of the centrifuge by increasing the distance a particle must travel to reach the wall. Liquid from the feed spills over a weir at the top of the bowl. When the thickness of sediment collecting in the bowl reaches the position of the liquid-overflow weir, separation efficiency declines rapidly. This limits the capacity of the centrifuge.

5. At what speed do you centrifuge blood?
a) 2200-2500 RPM
b) 3000-3200 RPM
c) 1000-1500 RPM
d) 4000 RPM

View Answer

Answer: a [Reason:] Do not centrifuge immediately after drawing blood. Allow the blood to clot in an upright position for at least 30 minutes but not longer than 1 hour before centrifugation. Perform venipuncture as with any other blood collection device. Centrifuge for at least 15 minutes at 2200-2500 RPM within one hour of collection.

6. Which of the following centrifugation is used to separate certain organelles from whole cell?
a) Rate-zonal centrifugation
b) Normal centrifugation
c) Differential centrifugation
d) Isopycnic centrifugation

View Answer

Answer: c [Reason:] The simplest form of separation by centrifugation is differential centrifugation, sometimes called differential pelleting. Particles of different densities or sizes in a suspension will sediment at different rates, with the larger and denser particles sedimenting faster. These sedimentation rates can be increased by using centrifugal force. A suspension of cells subjected to a series of increasing centrifugal force cycles will yield a series of pellets containing cells of decreasing sedimentation rate. Differential centrifugation is a common procedure in microbiology and cytology used to separate certain organelles from whole cells for further analysis of specific parts of cells.

7. A viscous solution contains particles with a density is to be clarified by centrifugation. The solution density is and its viscosity is 80 cp. The centrifuge has a bowl with and 3 1200 / p ρ = kg m 3 ρ = 850 / kg m 2r m = 0.02 1 r = 0.01 m and height b=0.25 m. Calculate the critical particle diameter of the largest particles in the exit stream if N=15000 rpm and flow rate q=0.002 m3 /hr?
a) 2.9 μm
b) 2.66 μm
c) 3.15 μm
d) 2.57 μm

View Answer

Answer: d [Reason:] bioprocess-engineering-questions-answers-centrifugation -q7-1

8. Which of the following is used as a media for density gradient?
a) Agarose
b) Ficoll
c) Luria broth
d) Propylene glycol

View Answer

Answer: b [Reason:] Ficoll is a neutral, highly branched, high-mass, hydrophilic polysaccharide which dissolves readily in aqueous solutions. Ficoll is part of Ficoll-Paque, which is used in biology laboratories to separate blood to its components (erythrocytes, leukocytes etc.). Ficoll-Paque is normally placed at the bottom of a conical tube, and blood is then slowly layered above Ficoll-Paque.

9. From the following which is the type of filtration centrifuge?
a) Screen/scroll centrifuge
b) Tubular centrifuge
c) Decanter centrifuge
d) Separator centrifuge

View Answer

Answer: a [Reason:] For the filtration or the so-called screen centrifuge the drum is perforated and is inserted with a filter, for example a filter cloth, wire mesh or lot screen. The suspension flows through the filter and the drum with the perforated wall from the inside to the outside. In this way the solid material is restrained and can be removed. The kind of removing depends on the type of centrifuge, for example manually or periodically.

10. Which of the following is used in uranium enrichment?
a) Tubular centrifuge
b) Disk-stack centrifuge
c) Gas centrifuge
d) Zippe-type centrifuge

View Answer

Answer: c [Reason:] Gas centrifuges are used in uranium enrichment. The heavier isotope of uranium (uranium-238) in the uranium hexafluoride gas tends to concentrate at the walls of the centrifuge as it spins, while the desired uranium-235 isotope is extracted and concentrated with a scoop selectively placed inside the centrifuge. It takes many thousands of centrifugations to enrich uranium enough for use in a nuclear reactor (around 3.5% enrichment), and many thousands more to enrich it to weapons-grade (above 90% enrichment) for use in nuclear weapons.

11. What is the applied centrifugal field at a point equivalent to 5 cm from the centre of rotation and an angular velocity of 3000 rad s-1?
a) 4.5 × 10-7 cm s-2
b) 5.4 × 10-7 cm s-2
c) 3.4 × 10-7 cm s-2
d) 6.5 × 10-7 cm s-2

View Answer

Answer: a [Reason:] The centrifugal field G, at a point 5 cm from the centre of rotation may be calculated using the equation G= ω2 r, G= (3000)2 × 5 cm s-2 = 4.5 × 10-7 cm s-2.

12. For the pelleting of the microsomal fraction from a liver homogenate, an ultracentrifuge is operated at a speed of 40000 rpm. What is the angular velocity, ω, in radians per second?
a) 3888.8 rad s-1
b) 5680.8 rad s-1
c) 4188.8 rad s-1
d) 4288.8 rad s-1

View Answer

Answer: c [Reason:] The angular velocity, ω, may be calculated using the equation: ω = (2 π rev min-1 )/60 ω = 2 × 3.1416 × 40000/60 rad s-1 = 4188.8 rad s-1.

13. What is a rate-zonal centrifugation?
a) Based on separation of particles by mass
b) Based on separation of particles by density
c) Based on separation of particles on solubility
d) Based on separation of particles on size

View Answer

Answer: d [Reason:] Rate-zonal centrifugation is a centrifugation technique employed to effectively separate particles of different sizes. Once the centrifugation is over, fractions are collected.

Set 5

1. Which type of mechanism is applicable to chromatography?
a) Absorption and Desorption
b) Adsorption and Absorption
c) Adsorption and Desorption
d) Adsorption and Diffusion

View Answer

Answer: c [Reason:] Adsorption means the attraction to a substance (as opposed to absorption, which means the complete envelopment of something). Desorption is the opposite – when something is not attracted to the substance. How it relates to chromatography is through the mobile and stationary phase. Depending on what the substance adsorbs or desorbs to, will determine how it will move in the chromatogram. For example, if it adsorbs to the mobile phase, it will move a lot. However, if it adsorbs to the stationary phase, it will not move very much. This is how mixtures are separated through chromatography, as different substances in the mixture will adsorb and desorb differently, and hence will move differently, and thus separation is achieved.

2. Which of the following condition is of reverse phase chromatography?
a) The mobile phase is non-polar and stationary phase is polar
b) The mobile phase is polar and stationary phase is non-polar
c) Both the mobile phase and stationary phase are organic
d) Both the mobile phase and stationary phase are inorganic

View Answer

Answer: b [Reason:] In reversed phase chromatography, the mobile phase is polar (like water), and the stationary phase is non-polar while in normal phase chromatography, the mobile phase is non-polar (100% organic), and the stationary phase is polar.

3. Which of type of chromatography depends on the principle of size of particles?
a) Affinity chromatography
b) Gel- filtration chromatography
c) Ion- exchange chromatography
d) Multimodal chromatography

View Answer

Answer: b [Reason:] Gel filtration chromatography, a type of size exclusion chromatography, can be used to either fractionate molecules and complexes in a sample into fractions with a particular size range, to remove all molecules larger than a particular size from the sample, or a combination of both operations.

4. According to the small size of the particle, which type of chromatographic separation is applicable?
a) High- performance liquid chromatography (HPLC)
b) Fast protein liquid chromatography (FPLC)
c) Gel chromatography
d) Paper chromatography

View Answer

Answer: a [Reason:] In order to achieve the high resolutions characteristic of HPLC, stationary-phase particles 2-5 μm in diameter are commonly used. Because the particles are so small, HPLC systems are operated under high pressure (5-10 MPa) to achieve flow rates of 1-5 ml min -1. FPLC instruments are not able to develop such high pressures (1-2 MPa), and are therefore operated with column packings of larger size.

5. The visual output of chromatography is called?
a) Chromatograph
b) Chromatogram
c) Electropherogram
d) Autoradiogram

View Answer

Answer: b [Reason:] The machine used is called a gas or liquid chromatograph, the data generated is called a chromatogram. It is an electronic file or hardcopy containing the information generated during the chromatography run.

6. From the graph given which component has the higher elution rate?
a) A
b) B
c) A & B
d) None of the mentioned

View Answer

Answer: b bioprocess-engineering-questions-answers-chromatography -q6 [Reason:] Because Component A is adsorbed more strongly than B, and B is desorbed easily and has higher rate of elution as has the greater affinity towards the Stationary phase, As the solutes move through the stationary phase they separate.

7. In which of the following type of chromatography the capillary action mechanism is present?
a) Liquid chromatography
b) Gas chromatography
c) Thin- Layer chromatography
d) Paper chromatography

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Answer: d [Reason:] The most common type of chromatography. The paper is the stationary phase. This uses capillary action to pull the solutes up through the paper and separate the solutes.

8. What does the retention factor, k’, describe?
a) The velocity from the stationary phase
b) The velocity of the mobile phase
c) The distribution of an analyte between the stationary and the mobile phase
d) The migration rate of an analyte through a column

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Answer: d [Reason:] k’ (Capacity factor) in the chromatography is to provide a calculation or formula which defines how much interaction the solute has with the stationary phase material. And it is based on the formula given below:

bioprocess-engineering-questions-answers-chromatography -q8

Where, T (R) = Retention time of the peak in minutes T (0) = Retention time of an unretained peak k’ value should be >1.

9. T (0) found to be 2.60 minutes and the sample elutes at 5.70 minutes. Calculate the value of k’ and find the correct answer.
a) 1.00
b) 1.19
c) 1.50
d) 2.00

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Answer: b [Reason:] bioprocess-engineering-questions-answers-chromatography -q9

10. Theoretical plates are used to ___________
a) Determine the thickness of the mobile phase
b) Determine the thickness of the stationary phase
c) Estimate the efficiency of the column
d) Measure the distribution of the analyte between mobile and stationary phases

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Answer: c [Reason:] The plate model supposes that the chromatographic column is contains a large number of separate layers, called theoretical plates. Separate equilibrations of the sample between the stationary and mobile phase occur in these “plates”.

11. What useful information can be found from a Van Deemter plot?
a) Optimum column length
b) Optimum column temperature
c) Optimum mobile phase flow rate
d) The selectivity factor

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Answer: a [Reason:] The Van Deemter equation is an empirical formula describing the relationship between plate height (H, the length needed for one theoretical plate) which is a measure of column efficiency, and linear velocity (µ) . Smaller plate height values corresponds to greater peak efficiencies, as more plates, or analyte partitioning, can occur over a fixed length of column. The Van Deemter equation is governed by three cumulative terms: (A) eddy diffusion, (B) longitudinal diffusion, and (C) mass transfer. A loss in peak efficiency can be observed as a wider analyte band, and therefore, these three terms can also be viewed as factors that contribute to band broadening.

12. The paper is non-polar in paper chromatography.
a) True
b) False

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Answer: b [Reason:] Polar components will be attracted to the water molecules attached to the cellulose (paper) and not attracted to a nonpolar solvent. The chromatogram will not contain the polar components, given that it doesn’t climb up the paper with the nonpolar solvent.