Biotechnology - MCQ Practice Questions

DMEM is the most widely used culture medium for mammalian/animal cell culture due to its balanced nutrient composition. LB broth is for bacteria, PDA for fungi, and Czapek Dox for fungi.

Laminar flow hoods create unidirectional airflow through HEPA filters, maintaining a sterile environment and preventing microbial contamination during cell culture operations.

Continuous cell lines (like HeLa, CHO) have unlimited replicative potential due to telomerase activation or genetic modifications, allowing indefinite division unlike primary cultures.

Mammalian cells require a pH of 7.2-7.4 (physiological pH) for optimal growth. This is maintained using buffers like bicarbonate or HEPES in culture media.

Fetal Bovine Serum (FBS) contains essential growth factors, hormones, and attachment factors that promote cell growth and proliferation in culture.

Cell doubling time indicates the rate at which cells divide and reflects their growth kinetics and overall health. It's calculated from exponential growth phase data.

Heating damages cells. Proper cryopreservation uses liquid nitrogen (-196°C) with cryoprotectants like DMSO or glycerol to prevent ice crystal formation that damages cell membranes.

The Hayflick limit describes the maximum replicative potential of normal human cells (~50-70 divisions) due to telomere shortening, after which cells enter senescence.

Trypan blue is a vital dye that enters dead/damaged cells but is excluded by viable cells with intact membranes, allowing quick assessment of post-thaw viability.

Serum-free media have defined, known compositions without variable components of serum, providing better reproducibility in research and reducing lot-to-lot variability.

Contact inhibition is a regulatory mechanism where normal cells cease dividing once they form a complete monolayer and contact neighboring cells, unlike transformed cells.

Bacterial contamination typically causes increased acidity, turbidity, and odor but suppresses mammalian cell growth due to competition and toxins. Mammalian cell division rate would decrease, not increase.

5% CO₂ is standard in mammalian cell culture incubators. It helps maintain pH (7.2-7.4) by forming a carbonate buffer system with bicarbonate in the medium.

Cell culture is crucial for pharmaceutical companies in India to conduct in vitro drug screening and toxicity testing, reducing reliance on animal testing per regulatory guidelines.

Primary cells have limited replicative lifespan due to the Hayflick limit and may undergo changes over passages, whereas continuous cell lines can divide indefinitely.

Even at normal density, cells require optimal osmolarity (280-320 mOsm/kg) and adequate nutrients. Nutrient depletion reduces metabolic activity and protein synthesis despite maintained cell count.

Vero (monkey kidney), CHO (hamster ovary), and HEK293 (human embryonic kidney) cells are widely used for vaccine production including COVID-19 and other vaccines in India.

Scale-up follows a logical progression from small (flask) to larger volumes, with each step validated for maintaining cell viability, growth rate, and product quality.

Mycoplasma is an obligatory contaminant in cell cultures that can affect cell behavior and product quality. Detection via PCR, culture, or ELISA is mandatory in biopharmaceutical manufacturing per ICH guidelines.

Perfusion systems continuously exchange medium, removing metabolic wastes and supplying nutrients, enabling higher cell densities and prolonged culture periods compared to batch systems.