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Ted’s Review Session

Overview of Cell Signaling and Immune Response

  • Cells signal the immune system about their health status:

    • Normal, abnormal, or needing destruction.

    • MHC (Major Histocompatibility Complex) proteins play a key role in this signaling.

Antigen Presentation

  • MHC Class II Proteins:

    • Present antigens from outside the cell.

    • Involvement of Antigen Presenting Cells (APCs) like macrophages:

      • Perform phagocytosis to ingest the antigen.

      • Digest the antigen and present it using MHC Class II to T helper cells.

      • Secrete cytokines to activate T helper cells.

  • MHC Class I Proteins:

    • Present antigens from infected or abnormal cells to cytotoxic T cells.

    • Essential for T helper cells to recognize antigens.

B Cells and Antigen Recognition

  • B cells can recognize antigens independently and also function as antigen presenting cells for T helper cells.

  • Significance of MHC:

    • MHC proteins are crucial for distinguishing self from non-self; their dysfunction can impair antigen recognition.

Membrane Structure and Drug Targeting

  • Cell membranes must stabilize using sterols:

    • Eukaryotic cells utilize cholesterol; prokaryotic cells do not.

  • Unique cell structures (e.g., ribosomes, cell walls) serve as targets for antibiotics:

    • Antibiotics can specifically target structures unique to prokaryotes, thus sparing eukaryotic cells (e.g., antibiotics targeting 70s ribosomes).

Endospores Survival Mechanism

  • Endospores are a survival strategy for bacteria in unfavorable conditions:

    • They are formed as a copy of DNA encased in a tough shell when conditions deteriorate.

    • Can survive for tens of thousands of years and become metabolically inactive until favorable conditions return.

    • Example: Clostridium endospores can lead to conditions like tetanus when they germinate in wounds.

Protozoa Characteristics

  • Protozoa are aquatic organisms without cell walls, making them fragile:

    • Exist as trophozoites (active form) or cysts (dormant form).

    • Movement methods include flagella, cilia, or amoeboid movement.

Cytosol and Prokaryotic Features

  • Prokaryotic cells always have certain structures like:

    • Peptidoglycan cell walls

    • Lipopolysaccharide in Gram-negative bacteria, a trigger for immune responses.

Immune Response Dynamics

  • The immune system recognizes danger patterns (e.g., peptidoglycan, lipopolysaccharides):

    • Overstimulation can lead to excessive immune responses, which may be harmful to the host.

Bacteria Diversity and Genetic Transfer

  • Binary fission is the primary reproduction method in bacteria but lacks genetic diversity:

    • Conjugation allows for genetic exchange between cells improving survival under selective pressure (e.g., antibiotic resistance).

Antibody and Cytokine Interactions

  • Cytokines from T helper cells instruct immune cells to activate, divide, or differentiate:

    • Regulation of immune response based on the threat level.

  • Antibodies interact with pathogens, blocking infections before they occur.

Microscopy Techniques

  • Different microscopy methods have their respective applications:

    • Bright field for general use.

    • Dark field, phase contrast, fluorescence, and electron microscopy for specialized observations of various microbial structures.