Mi exam 1

1. What is the biggest difference between a prokaryotic and eukaryotic cell?
   Answer: Prokaryotic cells do not have a nucleus; eukaryotic cells do have a nucleus.

2. What color are Gram-positive bacteria after a Gram stain?
   Answer: Purple

3. What color are Gram-negative bacteria?
   Answer: Pink/red

4. Which has the thicker peptidoglycan layer?
   Answer: Gram-positive bacteria

5. Which has an outer membrane containing LPS?
   Answer: Gram-negative bacteria

6. What does bactericidal mean?
   Answer: Kills bacteria

7. What does bacteriostatic mean?
   Answer: Stops bacteria from growing/reproducing

8. What does MIC stand for?
   Answer: Minimum Inhibitory Concentration

9. What does an MIC measure?
   Answer: The lowest concentration of an antimicrobial that prevents visible bacterial growth.

10. What are the two arms of the immune system?
    Answer: Innate immunity and adaptive immunity

11. Which arm responds rapidly and recognizes common patterns?
    Answer: Innate immunity

12. Which arm is highly specific and develops memory?
    Answer: Adaptive immunity

13. Where do B cells mature?
    Answer: Bone marrow
    🧠 B = Bone marrow

14. Where do T cells mature?
    Answer: Thymus
    🧠 T = Thymus

15. What are three examples of secondary lymphoid organs/tissues?
    Answer: Lymph nodes, spleen, and MALT

16. What is the basic function of lymph nodes?
    Answer: They filter lymph and provide a place for immune cells to encounter antigens.

17. Which immune cell is a rapid responder to bacterial infection?
    Answer: Neutrophil
    🧠 Neutrophils = NOW

18. What is the main job of macrophages?
    Answer: Phagocytosis (engulfing/eating microbes and debris)

19. Which cell is especially important for presenting antigen and connecting innate to adaptive immunity?
    Answer: Dendritic cell

20. What do NK cells kill?
    Answer: Virus-infected cells and abnormal/tumor cells

21. What are eosinophils strongly associated with?
    Answer: Parasites and allergic responses

22. What do B cells eventually produce through plasma cells?
    Answer: Antibodies

23. What is the main job of CD4 helper T cells?
    Answer: Coordinate/direct the immune response by helping activate other immune cells.
    🧠 CD4 = Commander

24. What is the main job of CD8 cytotoxic T cells?
    Answer: Kill infected or abnormal cells.
    🧠 CD8 = Destroy

25. What are the three categories of physical barriers?
    Answer: Mechanical, chemical, and biological

26. Is stomach acid a mechanical, chemical, or biological barrier?
    Answer: Chemical

27. Is normal microbiota a mechanical, chemical, or biological barrier?
    Answer: Biological

28. What does PAMP stand for?
    Answer: Pathogen-Associated Molecular Pattern
    🧠 P = Pathogen

29. What does DAMP stand for?
    Answer: Damage-Associated Molecular Pattern
    🧠 D = Damage

30. What does PRR stand for?
    Answer: Pattern Recognition Receptor

31. What is the difference between a PAMP and a DAMP?
    Answer:

• PAMP = pattern associated with microbes/pathogens

• DAMP = signal associated with damaged/stressed host cells

32. What do PRRs recognize?
    Answer: PAMPs and DAMPs

33. Where can TLRs be located?
    Answer: On the cell surface and on endosomal membranes inside the cell

34. Where are NLRs located?
    Answer: In the cytoplasm

35. Which PRRs are especially important for detecting viral RNA?
    Answer: RIG-I-like receptors (RLRs)

36. Why are some PRRs located on the cell surface while others are inside the cell?
    Answer: Because microbes or their components can be found in different locations. PRRs are positioned where they’re likely to encounter their specific targets.

⭐ Know these cold

Gram + = Purple + thick peptidoglycan
Gram − = Pink + thin peptidoglycan + outer membrane/LPS

Bactericidal = KILL
Bacteriostatic = STOP growth

Innate = FAST
Adaptive = SPECIFIC + MEMORY

B cell → Bone marrow → antibodies
T cell → Thymus
CD4 → Commander/helper
CD8 → Destroy/killer

PAMP = Pathogen
DAMP = Damage
PRR = Receptor that recognizes PAMPs/DAMPs

TLR = cell surface/endosome
NLR = cytoplasm
RLR = cytoplasm + viral RNA

Gram + → thick peptidoglycan → traps crystal violet → purple

Gram − → thin peptidoglycan + outer membrane → loses crystal violet → counterstain → pink/red

PAMP/DAMP → recognized by PRR → activates innate immune response

Innate response → dendritic-cell antigen presentation → helps activate adaptive response

B cell → plasma cell → antibodies
CD4 → coordinates
CD8 → kills

Prokaryotic vs. Eukaryotic Cells

Easy way to remember

Pro = primitive/simple

Bacteria are prokaryotes, so they do NOT have a nucleus.

2. COMMON ROUTES OF BACTERIAL INFECTION

Bacteria can enter the body through:

• Respiratory tract → breathing droplets

• GI tract → contaminated food/water

• Skin/wounds → cuts, bites, needles

• Genitourinary tract → sexual contact/urinary tract

• Blood → needles, transfusions, insect vectors

• Mother → baby → during pregnancy or birth

Think:

For an infection to happen, the organism needs a way into the body.

3. HOW BACTERIA ARE CLASSIFIED

Bacteria can be classified by several features.

Gram stain

• Gram-positive → purple

• Gram-negative → pink/red

Shape

• Cocci = round

• Bacilli = rods

• Spirilla/spirochetes = spiral

Oxygen requirements

• Aerobic = needs oxygen

• Anaerobic = does not need oxygen

• Facultative anaerobe = can live with OR without oxygen

Arrangement

• Diplo- = pairs

• Staphylo- = clusters

• Strepto- = chains

Positive = Purple + Plenty of peptidoglycan

Negative = Needs an extra outer membrane

Why does Gram-positive stay purple?

The thick peptidoglycan layer traps the crystal violet–iodine complex.

Gram-negative bacteria lose the purple stain during decolorization and then take up the counterstain, making them pink/red.

5. BACTERICIDAL VS. BACTERIOSTATIC

Bactericidal

Kills bacteria.

Think:

-cidal = kill

Like homicide = killing.

Bacteriostatic

Stops bacteria from growing/reproducing.

The immune system can then help eliminate them.

Think:

static = stays still

Flashcard

Q: What is the difference between bactericidal and bacteriostatic?

A: Bactericidal drugs kill bacteria; bacteriostatic drugs stop bacterial growth.

6. ANTIMICROBIAL SUSCEPTIBILITY

Antimicrobial susceptibility testing determines:

Which antibiotic is likely to work against a particular bacterium?

Results may classify the organism’s response to an antibiotic as:

• Susceptible → likely to respond at appropriate exposure

• Intermediate → may work under certain conditions/exposures

• Resistant → unlikely to work

7. MIC

MIC = Minimum Inhibitory Concentration

The MIC is:

The lowest concentration of an antimicrobial that prevents visible bacterial growth.

Important

Generally:

Lower MIC = less drug needed to inhibit that particular organism

But you cannot simply compare MIC numbers between different antibiotics and say the drug with the lowest number is automatically the best. Clinical breakpoints and achievable drug concentrations matter.

Flashcard

Q: What does MIC stand for?

A: Minimum Inhibitory Concentration.

Q: What does MIC tell you?

A: The lowest concentration of an antimicrobial needed to stop visible bacterial growth.

Antibiotics work because bacterial cells contain structures/processes we can target.

Major drug classes

Cell wall

• Penicillins

• Cephalosporins

• Carbapenems

• Vancomycin

Protein synthesis

• Macrolides

• Tetracyclines

• Aminoglycosides

• Clindamycin

• Linezolid

DNA/RNA

• Fluoroquinolones

• Rifamycins

• Metronidazole

Folate

• Sulfonamides

• Trimethoprim

9. IMMUNE SYSTEM

Immunity

Immunity = the body’s ability to protect itself from disease/infection.

Immune system

A network of:

Cells + tissues + organs + molecules

that work together to recognize and defend against harmful substances and organisms.

Main job

Recognize → respond → remove threat

10. TWO ARMS OF THE IMMUNE SYSTEM

Innate Immunity

You’re born with it.

• Fast

• Nonspecific

• First line of defense

• Recognizes common patterns

• Does not have the same highly specific memory response as adaptive immunity

Think:

Innate = Immediate

Adaptive Immunity

Develops a specific response against an antigen.

• Slower during first exposure

• Highly specific

• Uses B cells and T cells

• Creates immunologic memory

• Responds faster/stronger upon later exposure to the same antigen

Think:

Adaptive = Adjusts to a specific threat

11. PRIMARY VS. SECONDARY LYMPHOID ORGANS

Primary lymphoid organs

Where lymphocytes develop/mature.

Bone marrow

• Blood cells originate here

• B cells mature here

Thymus

• T cells mature here

Memory trick

B = Bone marrow

T = Thymus

Secondary lymphoid organs

Where mature immune cells can encounter antigens and become activated.

Examples:

• Lymph nodes

• Spleen

• Mucosa-associated lymphoid tissue (MALT)

Think:

Primary = preparation

Secondary = immune response gets started

12. LYMPHATIC SYSTEM

Lymph

Lymph is fluid that enters lymphatic vessels from the tissues.

It can contain:

• Water

• Proteins

• Immune cells

• Cellular debris

• Antigens/microorganisms

Basic pathway

Tissues → lymphatic vessels → lymph nodes → larger lymphatic vessels → bloodstream

Lymph nodes

Act like filters/checkpoints.

Immune cells inspect material traveling through the lymph.

13. CELLS OF THE IMMUNE SYSTEM

Innate immune cells

Neutrophils

Rapid responders to infection

• Phagocytose microbes

• Especially important in bacterial infections

• Often among the first immune cells recruited

Think: Neutrophils = NOW

Macrophages

Big eaters

• Phagocytosis

• Release cytokines

• Can present antigens to T cells

Monocytes

Circulate in the blood and can differentiate into macrophages or related cells after entering tissues.

Dendritic cells

Major antigen-presenting cells

They help connect:

Innate immunity → adaptive immunity

Natural Killer (NK) cells

Kill:

• Virus-infected cells

• Some abnormal/tumor cells

Eosinophils

Important for:

• Parasites

• Allergic responses

Basophils

Release inflammatory mediators such as histamine.

Associated with allergic/inflammatory responses.

Mast cells

Found mainly in tissues.

Release histamine and are important in:

• Allergic reactions

• Inflammation

• Defense against certain parasites

14. ADAPTIVE IMMUNE CELLS

B cells

Main job:

Antibody-mediated immunity

Activated B cells can become:

Plasma cells

Produce large amounts of antibodies.

Memory B cells

Help the body respond faster if exposed to the antigen again.

T cells

Helper T cells — CD4+

Coordinate/direct immune responses

They release signals that activate or regulate other immune cells.

Think:

CD4 = Commander

Cytotoxic T cells — CD8+

Kill infected or abnormal cells.

Think:

CD8 = Destroy

Memory T cells

Remain after an infection/exposure and allow a faster response later.

15. PHYSICAL BARRIERS

Physical barriers help stop microorganisms before they get inside tissues and cause infection.

Your objectives divide these into:

Mechanical barriers

Physically block or remove microbes.

Examples:

• Skin

• Mucous membranes

• Mucus

• Cilia

• Coughing

• Sneezing

• Urine flow

• Tears/washing action

Chemical barriers

Chemicals create an environment that kills or inhibits microbes.

Examples:

• Stomach acid

• Lysozyme

• Sebum

• Antimicrobial substances

• Low pH in certain body sites

Biological barriers

Your normal microbiota.

Good/normal microorganisms compete with harmful microorganisms for:

• Nutrients

• Space

Think:

Good bacteria make it harder for bad bacteria to move in.

16. ANTIGENS

Antigen

A substance or molecular structure that can be recognized by the immune system, particularly by antibodies or antigen receptors on lymphocytes.

Microorganisms contain many potential antigens.

Examples include components of:

• Bacterial surfaces

• Viral proteins

• Fungi

• Parasites

17. PAMPs

PAMP

Pathogen-Associated Molecular Pattern

These are conserved microbial structures/patterns recognized by the innate immune system.

Examples:

• LPS

• Peptidoglycan

• Flagellin

• Certain microbial nucleic acids

Memory trick

PAMP = Pathogen Pattern

DAMP

Damage-Associated Molecular Pattern

These are molecules/signals associated with damaged or stressed host cells/tissues that can trigger innate immune responses.

Easy memory

PAMP = Pathogen

DAMP = Damage

PRRs

Pattern Recognition Receptors

They are receptors used mainly by the innate immune system to recognize molecular patterns such as:

PAMPs + DAMPs

Think of PRRs as the body’s security sensors.

Simple relationship

PAMP/DAMP = thing being detected

⬇

PRR = detector

⬇

Immune response = alarm

20. IMPORTANT PRR CLASSES

Toll-like receptors — TLRs

Found on:

• Cell surface

• Endosomal membranes

They detect many microbial components.

Surface TLRs tend to detect microbial structures outside the cell, while endosomal TLRs can detect microbial nucleic acids that enter endosomes.

NOD-like receptors — NLRs

Found in the:

Cytoplasm

They recognize intracellular signals, including certain microbial products and cellular stress.

RIG-I-like receptors — RLRs

Found in:

Cytoplasm

Especially important for recognizing viral RNA.

C-type lectin receptors — CLRs

Commonly found on:

Cell surface

Recognize carbohydrate structures, especially those associated with organisms such as fungi.

PUTTING PRRs + PAMPs TOGETHER

This is the big concept your objectives are getting at:

Outside the cell

PRRs on the cell membrane can detect microbial components outside the host cell.

Inside an endosome

PRRs on endosomal membranes can detect microbial material, especially nucleic acids, taken into the cell.

Inside the cytoplasm

Cytoplasmic PRRs detect microbial components that make it into the host cell.

So the location of the PRR matches where its target is likely to appear.