BIO FINAL

What is a pathogen?

A disease-causing agent such as bacteria, viruses, fungi, or parasites

What is the immune system?

The collection of defenses that protect the body against pathogens

What is the main function of the immune system?

To distinguish self from nonself and eliminate foreign invaders

What is molecular recognition?

The specific binding of immune receptors to foreign molecules

What are the two types of immune defenses?

Innate immunity and adaptive immunity

What is innate immunity?

A fast, non-specific defense present in all animals

What is adaptive immunity?

A slower, specific defense found only in vertebrates that improves with exposure

What are barrier defenses?

The first line of defense that prevents pathogen entry

Name examples of barrier defenses

Skin, mucous membranes, secretions, stomach acid

Why can’t the body completely seal itself off?

Because it needs openings for gas exchange, nutrition, and reproduction

What is the role of mucus?

It traps pathogens and particles

What do ciliated epithelial cells do?

They sweep mucus and trapped pathogens out of the airway

What is lysozyme?

An enzyme that destroys bacterial cell walls

Where is lysozyme found?

Tears, saliva, and mucus

How does stomach acid protect the body?

Its low pH kills most pathogens in food and water

What pH is human skin and why is it important?

pH 3–5; inhibits bacterial growth

What happens if pathogens enter the body?

The immune system must recognize and destroy them internally

What is the key challenge once pathogens enter the body?

Distinguishing self from nonself

What do immune cells use to detect pathogens?

Receptor molecules that bind to foreign molecules

What is phagocytosis?

The process of engulfing and digesting pathogens

What are pseudopodia?

Extensions that surround and engulf pathogens

What happens after a pathogen is engulfed?

A vacuole forms and fuses with a lysosome

What destroys pathogens inside phagocytes?

Toxic compounds and lysosomal enzymes

What happens to debris after digestion?

It is expelled by exocytosis

What is the main barrier defense in insects?

The exoskeleton made of chitin

What is chitin?

A polysaccharide that forms a protective barrier

How do insects defend against viruses?

By destroying viral RNA using RNA interference

What is double-stranded RNA a sign of?

Viral infection

What does the enzyme Dicer-2 do?

Cuts viral RNA into small fragments

What does the Argo complex do?

Uses RNA fragments to destroy viral mRNA

What are Toll-like receptors (TLRs)?

Receptors that recognize common pathogen molecules

What do TLRs recognize?

Molecules like lipopolysaccharides, flagellin, and viral RNA

What are neutrophils?

Phagocytic cells that circulate in blood and respond to infection

What are macrophages?

Large phagocytic cells that engulf pathogens and reside in tissues

What are dendritic cells?

Cells that stimulate adaptive immunity after engulfing pathogens

What are eosinophils?

Cells that defend against parasitic worms by releasing enzymes

What are natural killer (NK) cells?

Cells that kill infected or cancerous cells by releasing chemicals

What do mast cells do?

Release histamine during inflammation

What is inflammation?

A response to injury or infection involving swelling, redness, and heat

What triggers inflammation?

Cytokines and histamine released by immune cells

What does histamine do?

Causes blood vessels to dilate and become permeable

Why does inflammation cause redness and heat?

Increased blood flow to the area

What is pus?

A mixture of dead white blood cells, pathogens, and tissue debris

What happens to fluid after inflammation?

It enters the lymphatic system as lymph

What is the lymphatic system?

A network that transports lymph and filters pathogens

What do lymph nodes do?

Contain immune cells that attack pathogens in lymph

What is systemic inflammation?

A body-wide inflammatory response

What can systemic inflammation cause?

Fever and increased white blood cells

What is septic shock?

A life-threatening systemic inflammatory response

What is chronic inflammation?

Long-term inflammation that damages tissues

What are interferons?

Proteins that inhibit viral replication

How do interferons work?

They signal nearby cells to block viral spread

What is the complement system?

A group of proteins that help destroy pathogens

What does the complement system do?

Causes lysis of pathogens and enhances inflammation

How can pathogens evade immunity?

By avoiding recognition or resisting destruction

What is an example of immune evasion?

Bacterial capsules that prevent phagocytosis

What is Mycobacterium tuberculosis?

A bacterium that survives inside immune cells

What disease does Mycobacterium tuberculosis cause?

Tuberculosis

What is an antigen?

A substance that triggers an immune response

What is an epitope?

The specific part of an antigen recognized by immune cells

What are lymphocytes?

White blood cells involved in adaptive immunity

What are the two main types of lymphocytes?

B cells and T cells

Where do B cells mature?

Bone marrow

Where do T cells mature?

Thymus

What do B cells recognize?

Intact antigens in body fluids

What do T cells recognize?

Antigen fragments presented on host cells

What is an antibody?

A soluble protein that binds specific antigens

What is another name for antibody?

Immunoglobulin (Ig)

What is the structure of a B cell receptor?

Y-shaped with two heavy and two light chains

What are variable regions?

Parts of receptors that vary and bind specific antigens

What are constant regions?

Parts of receptors that remain similar across cells

What is antigen presentation?

Display of antigen fragments on MHC molecules

What is MHC?

A protein that presents antigen fragments to T cells

Why is antigen presentation important?

It allows T cells to detect infected cells

What is receptor diversity?

The ability to recognize many different antigens

How is receptor diversity generated?

By gene rearrangement (V, J, C segments)

What is recombinase?

An enzyme that rearranges gene segments

What is self-tolerance?

The immune system’s ability to avoid attacking itself

How is self-tolerance achieved?

Self-reactive lymphocytes are destroyed or inactivated

What is clonal selection?

Activation and multiplication of specific lymphocytes

What is a clone?

A group of identical cells from one activated lymphocyte

What are effector cells?

Short-lived cells that actively fight infection

What are memory cells?

Long-lived cells that provide faster future responses

What is the primary immune response?

The first response to an antigen (slow and weak)

What is the secondary immune response?

A faster and stronger response to repeated exposure

What is immunological memory?

The ability to respond more effectively to previously encountered antigens

diffusion

when there is a difference in the concentration of a gas or other substance, such as between a cell and its immediate surroundings, ____ can result in net movement

gastrovascular cavity

structure in hydras, jellies, and cnidarians that functions in the distribution of substances throughout the body, as well as in digestion

heart

powers circulation by using metabolic energy to elevate the circulatory fluid’s hydrostatic pressure

Organ(s) that pump blood into vessels in a closed circulatory system

Open circulatory system

A system where circulatory fluid is not confined to vessels and directly bathes organs

Hemolymph

Circulatory fluid in an open system that also functions as interstitial fluid

Closed circulatory system

A system where blood is confined to vessels and separate from interstitial fluid

Blood

Circulatory fluid in a closed system that remains within vessels

Cardiovascular system

The organ system consisting of the heart and blood vessels that transports blood throughout the body

Arterioles

Small branches of arteries that regulate blood flow into capillary beds

Capillary beds

Networks of microscopic blood vessels where gas, nutrient, and waste exchange occurs

Venules

Small vessels that collect blood from capillaries and transport it toward veins

Veins

Blood vessels that carry blood back to the heart

Atria

Upper chambers of the heart that receive blood entering the heart

Ventricles

Lower chambers of the heart that pump blood out of the heart