BIOL251 EXAM 4 STUDY POINTS QUESTIONS WITH
CORRECT ANSWERS 2026 RATED A+
1. CH18 START
Explain humoral immunity and cellular immunity-ANSWER- - Humoral ’ B cell immunity
Eliminates EXTRAcellular antigens (bacteria, toxins, viruses in bloodstream)- Cellular ’ T cell
immunity
Eliminates INTRAcellular pathogens/antigens (viruses infecting cells, aberrant cells)
2. Define antigens and epitopes (antigenic determinants)-ANSWER- - Antigens ’ anything the
body
perceives as foreign
Food, viruses, bacteria, fungi, allergens- Epitopes ’ discrete regions of the antigen molecule
Typical protein can have multiple epitopes; different antibodies can bind to different epitopes of
the same antigen
3. What kind of molecules are the best antigens?-ANSWER- Big and complex molecules make
the best
antigens, and those that do big damage
4. Describe the structure of antibody molecule-ANSWER- - Are glycoproteins (protein + carb)
aka im
munoglobulins (Ig)- Y-shaped, held by disulfide bonds, made up of 2 light chains and 2 heavy
chains- Antigen binds at variable region (part of Fab region)
5. Explain the functions of antibodies-ANSWER- - Promotes phagocytosis, neutralize toxins or
viruses, activate
complement- Neutralization, Opsonization, Agglutination, Antibody-dependent cellular
cytotoxicity
6. Neutralization-ANSWER- Specific antibodies bind to antigens, prevents them from attaching
to target cells
7. Opsonization-ANSWER- Antibodies act as opsonins, tag pathogens for destruction by
macrophages, dendritic cells,
,neutrophils
8. Agglutination-ANSWER- Lumping of cells by binding to epitopes on 2 or more bacteria
simultaneously
9. Antibody-dependent cellular cytotoxicity-ANSWER- Antibodies bind to large pathogenic cell
too big for
phagocytosis, then bind to Fc receptors on membrane of NK cell
10. How do antibodies function as opsonins-ANSWER- Makes a bridge between pathogen
antigens and
phagocytic cells to initiate phagocytosis
11. What are the five classes of antibodies and their characteristics-ANSWER- - IgM ’ pentamer,
the first on the scene, agglutination and precipitation, initiate complement cascade- IgG ’
monomer, the first immunoglobulin gained by the cell (from placenta), most versatile
BIOL251 EXAM 4 STUDY POINTS
Study online at https-ANSWER-//quizlet.com/_id61oo- IgA ’ dimer, found in breast milk, tears,
saliva, neutralizer, important in mucosal immunity- IgD ’ monomer, on surface of B cells- IgE ’
monomer, attach to basophils and mast cells via Fc region that release chemical contents when
antigen binds to
IgE, like eosinophil (for parasites, inflammation, allergic reactions)
remember GAMED, these are the common immunoglobulins
12. What is the difference between T dependent and T independent antigens-ANSWER- -
T independent ’ non-protein antigens that can activate B cells w/o helper T cells- T dependent ’
B cells get activated by helper T cells by presenting protein antigen/epitopes + MHC II
13. How does an antibody response occur (what are the steps)-ANSWER- - Lag period ’ immune
system identifies new antigen and makes antibodies- End of lag phase ’ B cells differentiate into
plasma cells- 2 weeks after initial antigen exposure, IgM reaches peak levels- Helper T cells
stimulate class switching- After 3 weeks IgM declines, IgG increases- Some B cells differentiate
to memory cells- Secondary response to the same antigen is faster
14. Explain the primary and secondary antibody responses (and how they differ)
, -ANSWER- - Primary antibody response ’ a little slower because they're still trying to get used to
the virus- Secondary response ’ faster because there are B memory cells that do their thing and
get plasma cells (B cells that
make antibodies) out a lot faster
15. What are memory B cells? What is their role in immunity?-ANSWER- - B cells activated by
helper
T cells for activation- Cells that remember infections, have antigen specific receptors- They allow
for a faster response time- Provide long-term immunity
16. What are MHC class I and class II molecules?-ANSWER- - Involved in antigen presentation-
MHC class I ’ on all SELF cells, present normal self-antigens and abnormal/non-self pathogens to
effector T cells
involved in cellular immunity- MHC class II ’ ONLY on macrophages, dendritic cells, and B cells,
present abnormal/non-self pathogen antigens for
initial activation of T cells
BIOL251 EXAM 4 STUDY POINTS
Study online at https-ANSWER-//quizlet.com/_id61oo
17. What is an Antigen presentation?-ANSWER- Immune cells present antigens on their surfaces
for activation
of T cells
18. What cells are antigen presenting cells?-ANSWER- Cells that present antigens to helper T
cells to make
an adaptive immune response
19. What are the different classes of T cells and what does each do?-ANSWER- - Helper T cell ’
direct both cellular and humoral immunity; they recruit other cells through cytokines- Cytotoxic
T cells ’ carry out cellular immunity; they kill cells via apoptosis- Regulatory T cells ’ prevent
damaging responses (ex. autoimmunity)
20. What is the role of T helper cells in the antibody response?-ANSWER- - Recognize antigen
presented on MHC I (exogenous antigens)- They tell B cells to differentiate into plasma cells to
make antibodies- Assist with adaptive immune response
CORRECT ANSWERS 2026 RATED A+
1. CH18 START
Explain humoral immunity and cellular immunity-ANSWER- - Humoral ’ B cell immunity
Eliminates EXTRAcellular antigens (bacteria, toxins, viruses in bloodstream)- Cellular ’ T cell
immunity
Eliminates INTRAcellular pathogens/antigens (viruses infecting cells, aberrant cells)
2. Define antigens and epitopes (antigenic determinants)-ANSWER- - Antigens ’ anything the
body
perceives as foreign
Food, viruses, bacteria, fungi, allergens- Epitopes ’ discrete regions of the antigen molecule
Typical protein can have multiple epitopes; different antibodies can bind to different epitopes of
the same antigen
3. What kind of molecules are the best antigens?-ANSWER- Big and complex molecules make
the best
antigens, and those that do big damage
4. Describe the structure of antibody molecule-ANSWER- - Are glycoproteins (protein + carb)
aka im
munoglobulins (Ig)- Y-shaped, held by disulfide bonds, made up of 2 light chains and 2 heavy
chains- Antigen binds at variable region (part of Fab region)
5. Explain the functions of antibodies-ANSWER- - Promotes phagocytosis, neutralize toxins or
viruses, activate
complement- Neutralization, Opsonization, Agglutination, Antibody-dependent cellular
cytotoxicity
6. Neutralization-ANSWER- Specific antibodies bind to antigens, prevents them from attaching
to target cells
7. Opsonization-ANSWER- Antibodies act as opsonins, tag pathogens for destruction by
macrophages, dendritic cells,
,neutrophils
8. Agglutination-ANSWER- Lumping of cells by binding to epitopes on 2 or more bacteria
simultaneously
9. Antibody-dependent cellular cytotoxicity-ANSWER- Antibodies bind to large pathogenic cell
too big for
phagocytosis, then bind to Fc receptors on membrane of NK cell
10. How do antibodies function as opsonins-ANSWER- Makes a bridge between pathogen
antigens and
phagocytic cells to initiate phagocytosis
11. What are the five classes of antibodies and their characteristics-ANSWER- - IgM ’ pentamer,
the first on the scene, agglutination and precipitation, initiate complement cascade- IgG ’
monomer, the first immunoglobulin gained by the cell (from placenta), most versatile
BIOL251 EXAM 4 STUDY POINTS
Study online at https-ANSWER-//quizlet.com/_id61oo- IgA ’ dimer, found in breast milk, tears,
saliva, neutralizer, important in mucosal immunity- IgD ’ monomer, on surface of B cells- IgE ’
monomer, attach to basophils and mast cells via Fc region that release chemical contents when
antigen binds to
IgE, like eosinophil (for parasites, inflammation, allergic reactions)
remember GAMED, these are the common immunoglobulins
12. What is the difference between T dependent and T independent antigens-ANSWER- -
T independent ’ non-protein antigens that can activate B cells w/o helper T cells- T dependent ’
B cells get activated by helper T cells by presenting protein antigen/epitopes + MHC II
13. How does an antibody response occur (what are the steps)-ANSWER- - Lag period ’ immune
system identifies new antigen and makes antibodies- End of lag phase ’ B cells differentiate into
plasma cells- 2 weeks after initial antigen exposure, IgM reaches peak levels- Helper T cells
stimulate class switching- After 3 weeks IgM declines, IgG increases- Some B cells differentiate
to memory cells- Secondary response to the same antigen is faster
14. Explain the primary and secondary antibody responses (and how they differ)
, -ANSWER- - Primary antibody response ’ a little slower because they're still trying to get used to
the virus- Secondary response ’ faster because there are B memory cells that do their thing and
get plasma cells (B cells that
make antibodies) out a lot faster
15. What are memory B cells? What is their role in immunity?-ANSWER- - B cells activated by
helper
T cells for activation- Cells that remember infections, have antigen specific receptors- They allow
for a faster response time- Provide long-term immunity
16. What are MHC class I and class II molecules?-ANSWER- - Involved in antigen presentation-
MHC class I ’ on all SELF cells, present normal self-antigens and abnormal/non-self pathogens to
effector T cells
involved in cellular immunity- MHC class II ’ ONLY on macrophages, dendritic cells, and B cells,
present abnormal/non-self pathogen antigens for
initial activation of T cells
BIOL251 EXAM 4 STUDY POINTS
Study online at https-ANSWER-//quizlet.com/_id61oo
17. What is an Antigen presentation?-ANSWER- Immune cells present antigens on their surfaces
for activation
of T cells
18. What cells are antigen presenting cells?-ANSWER- Cells that present antigens to helper T
cells to make
an adaptive immune response
19. What are the different classes of T cells and what does each do?-ANSWER- - Helper T cell ’
direct both cellular and humoral immunity; they recruit other cells through cytokines- Cytotoxic
T cells ’ carry out cellular immunity; they kill cells via apoptosis- Regulatory T cells ’ prevent
damaging responses (ex. autoimmunity)
20. What is the role of T helper cells in the antibody response?-ANSWER- - Recognize antigen
presented on MHC I (exogenous antigens)- They tell B cells to differentiate into plasma cells to
make antibodies- Assist with adaptive immune response
