Rucete ✏ Biology In a Nutshell
1. First Line of Defense (Non-specific Barriers)
- Skin: Physical barrier with oily and acidic surface to block invaders
- Antimicrobial Proteins:
- Lysozyme in saliva and tears destroys bacterial cell walls
- Cilia: Sweep invaders out of the respiratory tract
- Gastric Juice: Destroys microbes in the stomach
- Symbiotic Bacteria: Inhibit growth of harmful microbes in the intestines
2. Second Line of Defense (Non-specific Responses)
- Phagocytes: White blood cells that engulf pathogens
- Neutrophils and monocytes (which become macrophages)
- Natural Killer (NK) Cells: Attack abnormal or infected cells
- Complement System: A group of proteins that help destroy pathogens by promoting phagocytosis or cell lysis
- Interferons: Proteins released by virus-infected cells to help neighboring cells resist infection
- Inflammatory Response:
- Triggered by histamine (from basophils) → causes vasodilation
- Increases blood flow and allows phagocytes to reach infected areas
- Redness, heat, swelling, and pain are common symptoms
3. Major Histocompatibility Complex (MHC)
- Proteins on cell surfaces used to identify self vs. non-self cells
4. Lymphocytes (Specific Immune Response)
a) B Cells (Humoral Response)
- Produce antibodies (immunoglobulins: IgA, IgD, IgE, IgG, IgM)
- Differentiate into:
- Plasma Cells: Produce antibodies
- Memory Cells: Provide long-term immunity
b) T Cells (Cell-Mediated Response)
- Recognize and respond to non-self cells
- Cytotoxic T Cells: Attack infected or abnormal cells
- Helper T Cells: Activate B cells and Cytotoxic T cells
Tags:
Biology in a nutshell