FYUG Even Semester Exam 2025
BTCDSM-252: Microbiology and Immunology
Full Marks: 70 | Pass Marks: 28 | Time: 3 Hours
UNIT-I
Question 1(a): State the structural features of viruses. 2 Marks
Viruses are acellular organisms that consist of a nucleic acid core (either DNA or RNA) surrounded by a protein coat called a capsid
. Some viruses also possess an outer lipid envelope derived from the host cell membrane.Question 1(b): Differentiate between algae and fungi. 2 Marks
- Algae: Autotrophic organisms containing chlorophyll that perform photosynthesis .
- Fungi: Heterotrophic organisms that lack chlorophyll and obtain nutrients through absorption (saprophytic or parasitic) .
Question 1(c): Point out the features of Chlorophyceae. 2 Marks
Members of Chlorophyceae (green algae) are characterized by the presence of chlorophyll a and b, stored food in the form of starch, and cell walls primarily composed of cellulose
.Question 2(a): Write a note on criteria for grouping microorganisms. Point out the features of ascomycetes, basidiomycetes and deuteromycetes. 4+6=10 Marks
Criteria for Grouping Microorganisms:
Microorganisms are grouped based on several taxonomic criteria including morphology (shape, size, flagella), staining characteristics (Gram reaction), physiological/biochemical properties (oxygen requirement, enzyme production), and molecular characteristics (16S rRNA sequencing)
.Features of Fungal Groups:
- Ascomycetes (Sac fungi): Produce sexual spores called ascospores within a sac-like structure known as an ascus .
- Basidiomycetes (Club fungi): Characterized by the production of basidiospores on a club-shaped structure called a basidium (e.g., mushrooms) .
- Deuteromycetes (Fungi Imperfecti): A polyphyletic group of fungi where a sexual stage (teleomorph) has not yet been observed; they reproduce primarily through asexual spores .
Question 2(b): Give an account of morphology of bacteria. Describe cell structure of bacteria with a labelled diagram. 3+7=10 Marks
Bacterial Morphology:
Bacteria exhibit diverse shapes: Cocci (spherical), Bacilli (rod-shaped), Spirilla (spiral), and Vibrio (comma-shaped)
. They may exist as single cells, pairs (diplo-), chains (strepto-), or clusters (staphylo-).Bacterial Cell Structure:
- Cell Wall: Provides rigidity and protection; composed of peptidoglycan .
- Plasma Membrane: Selectively permeable lipid bilayer involved in transport and energy production .
- Cytoplasm: Gel-like substance containing ribosomes, inclusion bodies, and the nucleoid .
- Nucleoid: Region containing the circular, double-stranded DNA chromosome .
- Plasmids: Extrachromosomal small circular DNA providing traits like antibiotic resistance .
- Flagella/Pili: Appendages for motility and attachment/conjugation respectively .
UNIT-II
Question 3(a): State the nutritional categories of microorganisms. 2 Marks
Microorganisms are categorized based on their energy and carbon sources: Photoautotrophs (light/CO2), Photoheterotrophs (light/organic carbon), Chemoautotrophs (inorganic chemicals/CO2), and Chemoheterotrophs (organic chemicals/organic carbon)
.Question 3(b): What is transduction in bacteria? 2 Marks
Transduction is a process of horizontal gene transfer in bacteria where DNA is transferred from a donor cell to a recipient cell by a bacteriophage (virus)
.Question 3(c): Give examples of any two symbiotic microorganisms. 2 Marks
- Rhizobium: Lives in root nodules of legumes for nitrogen fixation .
- Lichens: A symbiotic association between an alga (or cyanobacterium) and a fungus .
Question 4(a): Write notes on: (i) Growth curve in microbes (ii) Generation time in bacteria 5+5=10 Marks
(i) Growth curve in microbes:
When bacteria are grown in a closed system, they follow a predictable pattern consisting of the Lag phase (adaptation), Log/Exponential phase (rapid division), Stationary phase (growth = death), and Death phase (nutrient depletion)
.(ii) Generation time:
The time required for a bacterial population to double in number during the log phase is called generation time (or doubling time)
. It varies significantly depending on the species and environmental conditions.Question 4(b): Give a detailed account of bacterial conjugation and transformation. 5+5=10 Marks
Bacterial Conjugation:
Conjugation is the direct transfer of DNA between two bacterial cells that are in physical contact, typically mediated by a sex pilus and a fertility (F) plasmid
.Bacterial Transformation:
Transformation is the process by which a competent bacterial cell takes up "naked" DNA fragments from its surrounding environment and incorporates them into its own genome
.UNIT-III
Question 5(a): Write a note on sterilization. 2 Marks
Sterilization is the absolute destruction or removal of all forms of microbial life, including highly resilient bacterial endospores and viruses, from an object or environment
.Question 5(b): What is inoculation? 2 Marks
Inoculation is the intentional introduction of microorganisms into a sterile culture medium to initiate growth and cultivation
.Question 5(c): Write a note on autoclaving. 2 Marks
An autoclave uses pressurized steam (typically 121°C at 15 psi for 15-20 minutes) to achieve sterilization. It is the most effective and reliable method for heat-stable biological materials.
Question 6(a): Give an illustrated account of chemical methods for sterilization. 10 Marks
Chemical sterilization involves using gaseous or liquid agents to kill microbes. Common methods include:
- Ethylene Oxide (EtO): A highly penetrative gas used for heat-sensitive equipment (e.g., plastics, syringes) .
- Glutaraldehyde: A high-level disinfectant and sterilant for medical instruments .
- Formaldehyde: Used as a fumigant for rooms and laboratories .
- Alcohol (70% Ethanol/Isopropanol): Used as an antiseptic and disinfectant .
Question 6(b): Write notes on: (i) culture media (ii) Preparation of Pure Culture 5+5=10 Marks
(i) Culture Media:
Media provide the necessary nutrients for microbial growth. Types include Synthetic (defined), Complex (undefined), Selective (supports specific microbes), and Differential (distinguishes between microbes).
(ii) Preparation of Pure Culture:
The goal is to isolate a single species from a mixed population. Common techniques include the Streak Plate method (dilution across agar surface), Pour Plate method, and Spread Plate method to obtain isolated colonies.
UNIT-IV
Question 7(a): Differentiate between innate and adaptive immunity. 2 Marks
- Innate Immunity: Non-specific, immediate response present from birth (e.g., skin, phagocytes) .
- Adaptive Immunity: Highly specific, develops after exposure to pathogens, and possesses memory (e.g., antibodies, T-cells) .
Question 7(b): What is MALT? 2 Marks
MALT (Mucosa-Associated Lymphoid Tissue) is a system of lymphoid tissue found in various submucosal membrane sites of the body, such as the gastrointestinal and respiratory tracts, providing local immune protection
.Question 7(c): Differentiate between B-lymphocytes and T-lymphocytes. 2 Marks
- B-lymphocytes: Mature in bone marrow; responsible for humoral immunity (antibody production) .
- T-lymphocytes: Mature in the thymus; responsible for cell-mediated immunity (direct killing of infected cells) .
Question 8(a): Write short notes on: (i) B-cell activation (ii) Heavy chain gene transcription 5+5=10 Marks
(i) B-cell activation:
Occurs when a B-cell receptor (BCR) binds to its specific antigen. This often requires additional signals from Helper T-cells (T-dependent activation), leading to clonal expansion and differentiation into plasma cells and memory cells.
(ii) Heavy chain gene transcription:
Involves the V(D)J recombination process where specific gene segments (Variable, Diversity, Joining) are rearranged to form a functional heavy chain gene, which is then transcribed into mRNA for antibody synthesis
.Question 8(b): Describe the structure of immunoglobulins. Add a note on T-cell receptors. 10 Marks
Immunoglobulin (Antibody) Structure:
Antibodies are Y-shaped proteins consisting of four polypeptide chains: two identical heavy chains and two identical light chains, held together by disulfide bonds
. Each chain has a constant region and a variable region that forms the antigen-binding site.T-cell receptors (TCR):
The TCR is a membrane-bound protein on T-lymphocytes that recognizes processed antigen fragments presented by MHC molecules. It typically consists of an alpha and a beta chain.
UNIT-V
Question 9(a): Write the features of autoimmune diseases. 2 Marks
Autoimmune diseases result from a failure of the immune system to distinguish between "self" and "non-self," leading to the immune system attacking the body's own tissues and organs
.Question 9(b): Write a note on MHC molecules. 2 Marks
MHC (Major Histocompatibility Complex) molecules are cell surface proteins that display antigen fragments to T-cells. MHC Class I is found on all nucleated cells, while MHC Class II is found on specialized antigen-presenting cells.
Question 9(c): Give a short account of Systemic Lupus Erythematosus (SLE). 2 Marks
SLE is a chronic systemic autoimmune disease where the body produces antibodies against its own DNA and nuclear proteins, leading to widespread inflammation and damage in joints, skin, and kidneys
.Question 10(a): Describe the life cycle of HIV. Give a short account of Hashimoto's syndrome. 5+5=10 Marks
HIV Life Cycle:
- Binding/Fusion: Virus attaches to CD4 receptors on T-cells .
- Reverse Transcription: Viral RNA is converted to DNA by reverse transcriptase .
- Integration: Viral DNA is integrated into the host genome via integrase .
- Replication/Assembly: Host machinery produces new viral components .
- Budding: New virions leave the cell to infect others .
Hashimoto's Syndrome:
An autoimmune disorder where the immune system attacks the thyroid gland, causing chronic inflammation (thyroiditis) and often leading to an underactive thyroid (hypothyroidism)
.Question 10(b): Write notes on: (i) ELISA (ii) RIA 5+5=10 Marks
(i) ELISA (Enzyme-Linked Immunosorbent Assay):
A biochemical technique used to detect the presence of an antigen or antibody in a sample using an enzyme-linked detection system, producing a color change proportional to the concentration
.(ii) RIA (Radioimmunoassay):
A highly sensitive in vitro assay technique that uses radioisotopes (instead of enzymes) to measure the concentration of antigens or antibodies in biological fluids
.Exam Focus & Strategy
Important Concepts List
- Growth Phases: Memorize the specific metabolic state of cells in each phase .
- MHC Restriction: Understanding how T-cells "see" antigens .
- Bacterial DNA Transfer: Know the differences between Transformation, Conjugation, and Transduction .
Common Mistakes to Avoid
- Confusing Sterilization (total kill) with Disinfection (reduction of pathogens) .
- Mixing up the maturation sites of B-cells (Bone marrow) and T-cells (Thymus) .
- Forgetting to mention the specific role of Reverse Transcriptase in the HIV life cycle .
Answer Presentation Strategy
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- Always draw the Antibody (Y-shape) and Growth Curve diagrams when applicable [span_65](end_span).
- Use tables to compare Innate vs Adaptive immunity for better clarity .
- In HIV questions, list the steps of the life cycle chronologically .