Microbiology and Immunology Quiz

Blood Components

• Formed elements make up 44% of blood, including red blood cells (RBCs), white blood cells (WBCs), and platelets.
• The remaining 55% is plasma, containing nutrients, electrolytes (like sodium, potassium, and chloride), nitrogenous waste products (urea), and dissolved gases.

Red Blood Cell Structure and Function

• RBCs are biconcave disks.
• Lacking organelles, they use anaerobic respiration.
• This shape maximizes surface area for gas exchange.
• Hemoglobin, containing iron, facilitates oxygen transport.
• Lifespan is ~120 days.

Hematopoiesis

• Hematopoiesis is the production of red blood cells in red bone marrow.
• It occurs constantly due to RBCs' inability to reproduce.
• It is hormonally controlled.

White Blood Cell Types and Function

• Granulocytes:
  • Neutrophils: Most abundant (70%), first responders to infections, phagocytic.
  • Eosinophils: Fight parasitic infections and regulate allergic reactions (acidic-red).
  • Basophils: Involved in inflammatory responses (basic blue).
• Agranulocytes:
  • Lymphocytes: Produce antibodies (B cells) and destroy infected cells (T cells); spherical nucleus.
  • Monocytes: Differentiate into macrophages for long-lasting immune responses; large, U-shaped nucleus.

White Blood Cell Production

• WBC production is stimulated by colony-stimulating factors released from red bone marrow.

Platelets in Blood Clotting

• Platelets initiate hemostasis (stopping blood loss) through vascular spasm, platelet plug formation, and clot formation.
• The process involves converting prothrombin to thrombin, and fibrinogen to fibrin.

Immune System Components

• Intracellular Fluid (ICF): Fluid inside cells.
• Extracellular Fluid (ECF): Fluid outside cells, divided into plasma and interstitial fluid.
• Tissue Fluid Types: Transudate (regular leakage) and Exudate (during inflammation).

Lymphatic Drainage

• Interstitial fluid enters lymphatic capillaries and becomes lymph.
• Lymph flows through vessels with valves, filtered by lymph nodes.
• Two main lymphatic ducts: right lymphatic duct and thoracic duct.

Tonsils

• Tonsils (pharyngeal, palatine, lingual) help screen pathogens entering from air/food.

Primary and Secondary Immune Organs

• Primary: Thymus and bone marrow.
• Secondary: Spleen and lymph nodes.

Spleen Function

• Filters blood (not lymph).
• Destroys old or damaged RBCs.
• Acts as a blood reservoir.
• Contributes to immune competence.

Thymus Function

• Located in the superior mediastinum.
• Important for T lymphocyte maturation.
• Aids in the development of self-tolerance (preventing autoimmune disorders).
• Produces thymosin (hormone).

Red Bone Marrow Function

• Produces blood cells (hematopoiesis) from hematopoietic stem cells.

Pathogens

• Living: bacteria, fungi, protozoa, parasitic animals.
• Non-living: viruses, prions.

Bacterial Cell Wall

• Peptidoglycan provides structural support and protection from osmotic pressure.
• Gram-positive bacteria: Thick peptidoglycan layer.
• Gram-negative bacteria: Thin peptidoglycan layer with an outer membrane (endotoxins).
• Mycoplasma lack a cell wall; some bacteria possess a capsule.

Sterilization Methods

• Autoclaving (high-pressure steam at 121°C) is used to kill endospores.

Types of Antibiotics

• Bactericidal: Kill bacteria directly, inhibiting cell wall synthesis (penicillins, cephalosporins), or altering ribosomes (streptomycin)
• Bacteriostatic: Inhibit bacterial growth by blocking protein synthesis (tetracyclines), folic acid production (sulfonamides), or DNA replication (trimethoprim).
• Broad-spectrum: Affect many types of bacteria.
• Narrow-spectrum: Affect a smaller range of bacteria.

Antibiotic Resistance

• Antibiotic resistance arises from bacterial mutations, overuse, and incomplete courses.
• Common resistant strains include MRSA (methicillin-resistant Staphylococcus aureus) and MDR-TB (multidrug-resistant tuberculosis).

Discovery of Penicillin

• Alexander Fleming's accidental discovery of penicillin from Penicillium notatum.

Virus Structure

• Viruses consist of a nucleocapsid (genome + capsid), and sometimes, an envelope.
• The capsid protects the genetic material.
• Envelopes derive from host cells.
• Spikes (glycoproteins) on the envelope aid in attachment to host cells.

Retroviruses

• Retroviruses use reverse transcriptase to convert RNA to DNA and integrate it into the host's genome.
• HIV is an example.

Prions

• Misfolded proteins causing fatal neurodegenerative diseases (e.g., Creutzfeldt-Jakob disease, Mad Cow disease).

Immune System Defense Mechanisms

• First Line: Skin, mucus membranes, chemical barriers (acidic pH), and beneficial microbiota.
• Second Line: Phagocytosis, inflammation, fever, and antimicrobial proteins.
• Third Line: Antibody-mediated immunity and cell-mediated immunity.

Antibody Structure and Function

• Y-shaped protein with two heavy and two light chains, including Fab (variable antigen-binding region) and Fc (constant region).
• Classified into IgG, IgA, IgM, IgE, and IgD, with different functions based on location and role in immune responses like opsonization and agglutination.

Antigen-Presenting Cells (APCs)

• Cells (macrophages, dendritic cells, B cells) that process and present antigens to T cells through MHC molecules.

Primary vs. Secondary Immune Responses

• Primary: First encounter with an antigen; slow response, IgM first, then IgG production.
• Secondary: Subsequent encounters; faster and stronger response, IgG-dominated.

Immunity

• Natural: Acquiring immunity through infection or maternal antibodies.
• Artificial: Acquiring immunity through vaccines or immune serum.
• Active: Acquiring immunity through exposure to the antigen, inducing immune responses.
• Passive: Acquiring immunity through obtaining pre-formed antibodies.