(SEM III) THEORY EXAMINATION 2025-26 PHYSICAL PHARMACEUTICS I

SECTION A – Short Answer Section

This section contains short conceptual questions related to sterilization, disinfectants, microbial staining techniques, and microbiological indicators. These questions test the basic understanding of pharmaceutical microbiology and laboratory sterilization methods.

Question 1: Define Phenol Coefficient.

Answer:
Phenol coefficient is a measure used to evaluate the effectiveness of a disinfectant compared to phenol.

Formula:

Phenol Coefficient =
Dilution of disinfectant / Dilution of phenol

A phenol coefficient greater than 1 indicates that the disinfectant is more effective than phenol.

Question 2: What is Z Value?

Answer:
Z value is the temperature increase required to reduce the D-value by one log cycle during sterilization.

It helps determine the temperature sensitivity of microorganisms during heat sterilization.

Question 3: What is the Role of Mordant in Gram Staining?

Answer:
A mordant is a substance used to fix the primary stain to the bacterial cell wall.

In Gram staining, iodine acts as the mordant and forms a complex with crystal violet dye, allowing Gram-positive bacteria to retain the stain.

SECTION B – Long Answer Section

This section requires detailed explanations of microbiological laboratory techniques such as staining methods, antibiotic assays, and sterility testing procedures.

Question 1: Explain the Steps of Gram Staining.

Answer:

Gram staining is used to differentiate bacteria into Gram-positive and Gram-negative groups.

Steps involved:

Primary Staining:
Crystal violet is applied to stain all cells.

Mordant Application:
Iodine solution is added to fix the stain.

Decolorization:
Alcohol or acetone removes stain from Gram-negative bacteria.

Counterstaining:
Safranin stains Gram-negative bacteria pink.

Result:

Gram-positive bacteria → Purple

Gram-negative bacteria → Pink

Question 2: Explain the Cup Plate Method for Antibiotic Assay.

Answer:

The cup plate method is used to determine the potency of antibiotics.

Procedure:

Prepare agar plates with microorganisms.

Make small wells (cups) in the agar.

Add antibiotic solution into the wells.

Incubate the plates.

The zone of inhibition around the cup indicates antibiotic activity.
The larger the zone, the stronger the antibiotic effect.

Question 3: Explain Sterility Test of Ophthalmic Preparations.

Answer:

Sterility testing ensures that pharmaceutical products are free from microorganisms.

Procedure:

Samples are inoculated into sterile culture media.

Two types of media are used:

Fluid thioglycollate medium (for bacteria)

Soybean casein digest medium (for fungi)

Incubate for 14 days.

Observe microbial growth.

If no growth occurs, the preparation is considered sterile.

SECTION C – Descriptive Section

This section tests detailed knowledge of sterilization equipment, microbial growth, viruses, and applications of microbiology in pharmaceuticals.

Question 1: Explain the Functioning of an Autoclave.

Answer:

An autoclave is a device used for moist heat sterilization using steam under pressure.

Principle:
Steam at high pressure increases temperature and kills microorganisms.

Standard conditions:

121°C temperature

15 psi pressure

15–20 minutes

Applications:
Sterilization of culture media, surgical instruments, and laboratory equipment.

Question 2: Explain Phases of Bacterial Growth.

Answer:

Bacterial growth occurs in four phases:

Lag Phase:
Bacteria adapt to the environment.

Log Phase (Exponential Phase):
Rapid cell division occurs.

Stationary Phase:
Growth rate equals death rate.

Death Phase:
Cells die due to nutrient depletion.

Question 3: Applications of Cell Culture in Pharmaceutical Industry.

Answer:

Cell culture is widely used in pharmaceuticals for:

Vaccine production

Drug testing and toxicity studies

Production of monoclonal antibodies

Genetic research

Development of biological drugs

Cell culture techniques play an important role in modern biotechnology and medicine