Immunity A3.1 Flashcards
What are pathogens?
Pathogens are microorganisms or agents that cause disease in hosts. They include bacteria, viruses, fungi, and protists.
What is a Prokaryotic cell that can produce toxins?
bacteria
what are Non-cellular entities that hijack host cells to reproduce?
virsuses
what are ukaryotic organisms that cause diseases like athlete’s foot?
fungi
what are Single-celled eukaryotes, such as Plasmodium?
protists
what are the bodies frist line of defense against disease?
Skin & Mucous membranes
how does skin help protect the body against viruses?
the Tough outer layer (keratinized) prevents pathogen entry. Sebaceous glands secrete sebum, creating an acidic environment that inhibits microbial growth.
how do mucous membranes help protect the body against viruses?
Found in areas like the respiratory tract, they trap pathogens with mucus and expel them through ciliary action or sneezing. Enzymes like lysozyme in saliva break down bacterial cell walls.
what is the process of blood clotting?
When skin is breached, blood clotting prevents further pathogen entry.
Platelets adhere to the injury site and release clotting factors.
Clotting factors convert prothrombin into thrombin.
Thrombin catalyzes the conversion of fibrinogen into fibrin, forming a mesh that stabilizes the clot.
describe an Innate Immune System
Non-specific, immediate response. Includes barriers (skin, mucus) and cells like phagocytes and natural killer cells.
describe an Adaptive Immune System
Specific, slower response involving lymphocytes (B-cells and T-cells). It creates memory cells for long-term immunity
what are the key differences between an innate immune system and an adaptive immune system?
Speed: Innate is rapid; adaptive takes days.
Specificity: Adaptive targets specific pathogens, while innate does not.
what is a phagocyte?
a type of cell within the body capable of engulfing and absorbing bacteria and other small cells and particles.
how do Phagocytes help Infection Control?
Phagocytes, such as macrophages and neutrophils, engulf pathogens through phagocytosis:
Pathogen is recognized and engulfed.
The pathogen is enclosed in a vesicle (phagosome).
Lysosomes fuse with the phagosome, releasing enzymes that digest the pathogen.
Antigen fragments may be presented on the phagocyte’s surface, signaling other immune cells.
what are Lymphocytes?
white blood cells central to adaptive immunity
what do B-Lymphocytes do?
Produce antibodies specific to antigens.
what do T-Lymphocytes do?
Include helper T-cells (activate B-cells) and cytotoxic T-cells (destroy infected cells)
how do antibodies neutralize pathogens?
Antibodies neutralize pathogens by:
Binding to antigens and preventing infection.
Flagging pathogens for destruction by phagocytes.
how are b-lymphocytes activated and cloned?
When a B-cell encounters its specific antigen, it binds and internalizes it. A helper T-cell recognizes the same antigen and releases cytokines, activating the B-cell. The activated B-cell undergoes clonal expansion, forming:
Plasma cells: Secrete large amounts of antibodies.
Memory cells: Provide immunity against future infections.
what happens to b and t cells after infection?
After an infection, some B- and T-cells remain as memory cells. Upon re-exposure to the same pathogen:
Memory cells respond quickly, producing antibodies before symptoms develop.
This forms the basis of long-term immunity.
how is HIV transmitted?
Through blood, semen, vaginal fluids, and breast milk. Targeting helper T-cells, impairing the immune system.
what is AIDS?
The final stage of HIV infection, characterized by severe immune suppression and vulnerability to opportunistic infections.
How do antibiotics help infection?
Antibiotics kill bacteria by targeting processes like cell wall synthesis or protein production, which do not occur in human cells. Overuse has led to resistant strains, such as MRSA. Mechanisms of resistance include:
-Mutation of target sites.
-Efflux pumps to remove antibiotics.
-Enzymes that break down antibiotics.
what are zoonoses?
Zoonotic diseases that originate in animals and transfer to humans. Examples:
Rabies: Transmitted via bites from infected animals.
Avian Influenza: Spread from birds to humans through close contact.
