Raw materials for culture media MCQs With Answer provide B.Pharm students a focused way to master essential components used in microbiological media preparation. This concise guide covers raw materials such as peptones, agar, beef and yeast extracts, carbon and nitrogen sources, salts, buffers, indicators, gelling agents, and selective supplements — plus quality parameters like purity, endotoxin limits, and water quality. Emphasis on specifications, sterilization effects, storage, and handling helps students link theory to practical lab preparation and pharmaceutical microbiology QC. Ideal for exam revision, practical assessments, and interview prep. Now let’s test your knowledge with 50 MCQs on this topic.
Q1. Which raw material is primarily used as a solidifying agent in bacteriological media?
- Agar
- Peptone
- Glucose
Correct Answer: Agar
Q2. Which component supplies amino acids and peptides in culture media?
- Peptone
- NaCl
- Agar
- Phenol red
Correct Answer: Peptone
Q3. Yeast extract in media primarily provides which of the following?
- Vitamins and growth factors
- Solidifying properties
- pH buffering
- Antibacterial activity
Correct Answer: Vitamins and growth factors
Q4. Which carbon source is most commonly used in basic culture media?
- Glucose
- Sodium nitrate
- Magnesium sulfate
- Agarose
Correct Answer: Glucose
Q5. What is the role of sodium chloride (NaCl) in many culture media?
- Osmotic balance and ionic strength
- Solidification of media
- Provide complex nitrogen sources
- Act as a pH indicator
Correct Answer: Osmotic balance and ionic strength
Q6. Which of the following is considered a complex nitrogen source?
- Casein hydrolysate (peptone)
- Sodium phosphate
- Potassium chloride
- Distilled water
Correct Answer: Casein hydrolysate (peptone)
Q7. Which buffer is commonly used to maintain neutral pH in culture media?
- Phosphate buffer
- Acetate buffer
- Glycine buffer
- Ferric chloride
Correct Answer: Phosphate buffer
Q8. What is a critical quality attribute of raw materials for culture media?
- Purity and microbial contamination levels
- Color of the packaging
- Manufacturer logo design
- Shipment weight only
Correct Answer: Purity and microbial contamination levels
Q9. Which raw material is heat-labile and often sterilized by filtration rather than autoclaving?
- Antibiotics (e.g., gentamicin)
- Agar powder
- Peptone
- NaCl
Correct Answer: Antibiotics (e.g., gentamicin)
Q10. Water for preparation of culture media in pharmaceutical labs is usually specified as:
- Water for Injection (WFI)
- Tap water
- Natural spring water
- Distilled water from any source
Correct Answer: Water for Injection (WFI)
Q11. Which additive acts as a selective agent by inhibiting Gram-positive organisms?
- Colistin
- Casein
- Yeast extract
- Agar
Correct Answer: Colistin
Q12. What is the primary function of indicators like phenol red in media?
- Show pH changes due to microbial metabolism
- Increase osmotic strength
- Supply nitrogen
- Solidify the medium
Correct Answer: Show pH changes due to microbial metabolism
Q13. Which raw material provides a source of sulfate ions in media?
- Magnesium sulfate (MgSO4)
- Glucose
- Yeast extract
- Agar
Correct Answer: Magnesium sulfate (MgSO4)
Q14. Which gelling agent is derived from seaweed?
- Agar
- Gelatin
- Polyacrylamide
- Starch
Correct Answer: Agar
Q15. Which raw material would be avoided when cultivating strictly anaerobic bacteria exposed to oxygen?
- None; oxygen exposure is the issue, not a specific medium component
- Yeast extract
- Peptone
- Glucose
Correct Answer: None; oxygen exposure is the issue, not a specific medium component
Q16. What is the purpose of adding blood to certain culture media?
- Provide additional growth factors and hemolysis detection
- Act as a solidifying agent
- Lower the pH drastically
- Serve as an antibiotic
Correct Answer: Provide additional growth factors and hemolysis detection
Q17. Which of the following is used as a selective dye in MacConkey agar?
- Neutral red
- Coomassie blue
- Crystal violet
- Methylene blue
Correct Answer: Neutral red
Q18. Which medium component is most likely to cause batch-to-batch variability if not standardized?
- Complex extracts like yeast extract or peptone
- Sodium chloride
- Analytical grade glucose
- Distilled water filtered to WFI
Correct Answer: Complex extracts like yeast extract or peptone
Q19. Endotoxin contamination in raw materials is particularly critical for which type of testing?
- A pyrogenicity/endotoxin assay
- Gram staining
- Colony morphology assessment
- Motility tests
Correct Answer: A pyrogenicity/endotoxin assay
Q20. Which factor should be checked in agar intended for bacteriological use?
- Gel strength and clarity
- Protein content percentage
- Vitamin B12 concentration
- Fatty acid profile
Correct Answer: Gel strength and clarity
Q21. Which salt provides potassium ions important for bacterial growth?
- Potassium chloride (KCl)
- Sodium sulfate
- Calcium carbonate
- Magnesium phosphate
Correct Answer: Potassium chloride (KCl)
Q22. Which raw material is commonly used as a fermentable carbohydrate for lactose fermentation tests?
- Lactose
- Peptone
- NaCl
- Activated charcoal
Correct Answer: Lactose
Q23. Which of the following is a defined medium component often used to supply ammonium nitrogen?
- Ammonium sulfate ((NH4)2SO4)
- Yeast extract
- Peptone
- Agar
Correct Answer: Ammonium sulfate ((NH4)2SO4)
Q24. What precaution is important when storing powdered peptone?
- Store in a cool, dry place to prevent moisture and microbial growth
- Store in direct sunlight to keep it dry
- Keep it unsealed to allow aeration
- Freeze at -20°C without packaging
Correct Answer: Store in a cool, dry place to prevent moisture and microbial growth
Q25. Which component is used in selective media to inhibit Gram-negative bacteria?
- Bile salts
- Blood
- Glucose
- Yeast extract
Correct Answer: Bile salts
Q26. Which raw material provides nucleotides and growth factors often required by fastidious organisms?
- Yeast extract
- Sodium chloride
- Calcium carbonate
- Agar
Correct Answer: Yeast extract
Q27. For sterility assurance, what is an important test performed on incoming raw materials?
- Microbial load testing and certificate of analysis review
- Taste testing by lab staff
- Color matching against a chart
- Market price comparison
Correct Answer: Microbial load testing and certificate of analysis review
Q28. Why are some media components filter-sterilized at 0.22 µm?
- To remove microorganisms while preserving heat-sensitive components
- To increase nutrient concentration
- To change the pH
- To solidify the medium
Correct Answer: To remove microorganisms while preserving heat-sensitive components
Q29. Which carbohydrate is non-fermentable and used to test respiratory metabolism in some organisms?
- Glycerol
- Glucose
- Lactose
- Sucrose
Correct Answer: Glycerol
Q30. What is the role of divalent cations like Mg2+ and Ca2+ in culture media?
- Serve as enzyme cofactors and stabilize cell membranes
- Act as carbon sources
- Provide buffering capacity
- Serve as selective antibiotics
Correct Answer: Serve as enzyme cofactors and stabilize cell membranes
Q31. Which component is commonly added to detect hydrogen sulfide production?
- Ferrous ammonium sulfate or ferrous sulfate
- Glucose
- Yeast extract
- Agarose
Correct Answer: Ferrous ammonium sulfate or ferrous sulfate
Q32. Which preservative is sometimes added to media to prevent fungal contamination in selective formulations?
- pimaricin (natamycin)
- Peptone
- Magnesium sulfate
- Neutral red
Correct Answer: pimaricin (natamycin)
Q33. What is a common test to evaluate agar quality before use?
- Gel strength determination
- Protein electrophoresis
- Lipid profile testing
- Gas chromatography
Correct Answer: Gel strength determination
Q34. Which raw material would be inappropriate for media intended for lipid-requiring organisms?
- Media lacking lipid supplements like Tween 80 or oleic acid
- Yeast extract
- Peptone
- Glucose
Correct Answer: Media lacking lipid supplements like Tween 80 or oleic acid
Q35. What specification is critical for powdered media components used in sterile filtration?
- Solubility and particulate content
- Color intensity
- Vendor brand only
- Country of origin exclusively
Correct Answer: Solubility and particulate content
Q36. Which raw material is typically used to detect carbohydrate fermentation by pH change?
- Phenol red indicator with a fermentable sugar
- Magnesium chloride
- Agarose
- Potassium phosphate
Correct Answer: Phenol red indicator with a fermentable sugar
Q37. Which of the following is a defined synthetic medium component list advantage?
- Reproducibility and known chemical composition
- Lower cost than complex media in all cases
- Contains natural growth factors by default
- Requires no quality control
Correct Answer: Reproducibility and known chemical composition
Q38. For preparing culture media, why is pH adjustment before sterilization important?
- Autoclaving can change pH; correct initial pH ensures proper post-sterilization pH
- To color the medium for identification
- To solidify the medium during autoclave cycle
- pH adjustment is unnecessary for most media
Correct Answer: Autoclaving can change pH; correct initial pH ensures proper post-sterilization pH
Q39. Which raw material is commonly used to provide reducing conditions in anaerobic media?
- Cysteine or thioglycollate
- Sucrose
- Neutral red
- Agar
Correct Answer: Cysteine or thioglycollate
Q40. What is the effect of autoclaving complex extracts for too long?
- Degradation of heat-labile nutrients and browning (Maillard reactions)
- Increased nutrient potency
- Transformation into agar
- Complete sterilization without side effects
Correct Answer: Degradation of heat-labile nutrients and browning (Maillard reactions)
Q41. Which supplement is often added for cultivation of Neisseria species?
- Chocolate agar components (heated blood)
- High concentration NaCl
- High agar concentration
- Cellulose
Correct Answer: Chocolate agar components (heated blood)
Q42. Which raw material is essential in media used for fungal cultivation to reduce competing bacteria?
- Antibiotics such as chloramphenicol
- High glucose only
- Extra agar only
- Magnesium sulfate only
Correct Answer: Antibiotics such as chloramphenicol
Q43. What determines whether a medium is defined or complex?
- Whether all chemical components and concentrations are known
- The color of the medium
- The supplier brand
- Whether agar is included
Correct Answer: Whether all chemical components and concentrations are known
Q44. Which raw material would be added to select for Gram-positive organisms by inhibiting Gram-negative ones?
- Potassium tellurite or crystal violet-based agents in appropriate concentrations
- Yeast extract alone
- High glucose alone
- Agarose
Correct Answer: Potassium tellurite or crystal violet-based agents in appropriate concentrations
Q45. Which quality control test assesses sterility of prepared media batches?
- Incubation for absence of microbial growth (sterility test)
- pH measurement only
- Viscosity testing
- UV-Vis absorbance at 600 nm
Correct Answer: Incubation for absence of microbial growth (sterility test)
Q46. What is the main reason to avoid animal-derived raw materials when possible in pharma media?
- Risk of adventitious agents and variability
- They are always cheaper
- They always solidify poorly
- They are always colorless
Correct Answer: Risk of adventitious agents and variability
Q47. Which component is commonly used to chelate divalent cations and reduce metal availability?
- EDTA
- Glucose
- Yeast extract
- Agar
Correct Answer: EDTA
Q48. Which parameter of raw materials affects the osmotic pressure of media?
- Total solute concentration (e.g., salts, sugars)
- Color of the powder
- Packaging design
- Supplier address
Correct Answer: Total solute concentration (e.g., salts, sugars)
Q49. Which supplement is often added for cultivation of fastidious streptococci?
- Blood or serum (e.g., sheep blood)
- High concentration NaCl only
- Activated charcoal only
- Synthetic agar only
Correct Answer: Blood or serum (e.g., sheep blood)
Q50. When preparing media, why is batch documentation of raw material lot numbers important?
- Traceability for quality control and investigation of unexpected results
- To increase the market value of media
- To make the packaging heavier
- To allow random mixing of lots without records
Correct Answer: Traceability for quality control and investigation of unexpected results
I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.
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