MUCITCARP BAL • 242 SOIB
★ ★
Chamberlain University
C College of Nursing & Health Professions
J O U R N E Y T O E X T R A O R D I N A R Y CO M PA S S I O N AT E C A R E
EST. 1889
BIOS 242 — Lab Practicum Examination
M I C R O B I O LO G Y L A B O R ATO R Y T E C H N I Q U E S · M I C R O S CO P Y · STA I N I N G · I M M U N O LO G Y · S A F E TY
INSTITUTION Chamberlain University COURSE CODE BIOS 242
PROGRAM Bachelor of Science in Nursing (BSN) ACADEMIC YEAR
EXAM TITLE Lab Practicum — Microbiology Laboratory TOTAL QUESTIONS 25 Questions
COURSE TITLE Fundamentals of Microbiology FORMAT Multiple Choice — Select the Single Best Answer
LAB PR ACTICUM INSTRUCTIONS
▸ Select the single best answer for each question unless otherwise instructed.
▸ This practicum covers laboratory techniques, microscopy, Gram staining, fermentation testing, immunology, and aseptic technique.
▸ All content reflects BIOS 242 lab learning objectives.
▸ Correct answers and detailed rationales appear below each question for exam preparation purposes.
▸ Pay careful attention to Gram stain steps, fermentation results interpretation, and antibody structure/function.
SECTION I — LAB TECHNIQUES, MICROSCOPY, STAINING, FERMENTATION & IMMUNOLOGY Questions 1 – 25
1. Which culture method uses liquid nutrient media to grow bacteria?
A. Slant culture
B. Stab culture
C. Broth culture
D. Plate culture
CORRECT ANSWER C — Broth culture
RATIONALE Broth culture uses liquid nutrient media to grow bacteria — it provides a large surface area for bacterial growth in suspension. A slant culture is solid nutrient agar
solidified at an angle in a tube. A stab culture involves deep inoculation of nutrient agar using an inoculating needle. Sterile broth and sterile slant contain no
microorganisms. The inoculating loop is used to transfer bacteria across surfaces; the inoculating needle is used for stabbing or precise transfer. These tools are
sterilized using an incinerator before and after use.
2. Which microscope part controls the amount of light reaching the specimen?
A. Eyepiece lens — the lens you look through, usually 10x
B. Objective lenses — primary magnification lenses
C. Diaphragm or iris — adjusts light intensity
D. Arm — supports the microscope for carrying
CORRECT ANSWER C — Diaphragm or iris — adjusts light intensity
RATIONALE The diaphragm (or iris diaphragm) controls the amount of light reaching the specimen by adjusting the aperture. The condenser lens focuses light onto the
specimen. The eyepiece lens (ocular) is what you look through, typically 10x magnification. Objective lenses provide primary magnification (4x, 10x, 40x, 100x).
The stage holds the slide. The coarse adjustment knob moves the stage quickly for initial focus; the fine adjustment knob sharpens focus under high power. A
parfocal objective allows the microscope to stay approximately in focus when switching between lenses. The field of view is the visible area.
3. The correct sequence of steps in a Gram stain procedure is:
A. Safranin → Iodine → Decolorizer → Crystal Violet
B. Crystal Violet (primary stain) → Iodine (mordant) → Decolorizer (alcohol/acetone) → Safranin (counterstain)
C. Iodine → Crystal Violet → Safranin → Decolorizer
D. Decolorizer → Safranin → Crystal Violet → Iodine
CORRECT ANSWER B — Crystal Violet → Iodine → Decolorizer → Safranin
RATIONALE Gram stain procedure: (1) Crystal Violet — primary stain, colors ALL bacteria purple; (2) Iodine — mordant that fixes crystal violet in Gram-positive cells by forming
a crystal violet-iodine complex; (3) Decolorizer — alcohol or acetone that removes the stain from Gram-negative cells (which have a thin peptidoglycan layer and
outer membrane); (4) Safranin — counterstain that colors now-colorless Gram-negative bacteria pink. Gram-positive result: purple cells (thick peptidoglycan
retains crystal violet). Gram-negative result: pink cells (stain washed out, safranin taken up). A thin smear is heat-fixed to prepare bacteria for staining.
, 4. The purpose of the multi-stroke streak pattern is to:
A. Mix multiple bacterial species together in one plate
B. Separate bacteria to obtain pure, isolated colonies by progressively diluting the sample across the agar surface
C. Sterilize the agar surface before inoculation
D. Measure the growth rate of bacteria in liquid culture
CORRECT ANSWER B — Separate bacteria to obtain pure, isolated colonies by progressively diluting the sample
RATIONALE The multi-stroke streak pattern (quadrant streak) uses four sequential streaks to progressively dilute bacterial sample across the agar plate surface. Each streak
pulls fewer bacteria from the previous quadrant, eventually producing individual cells that multiply into pure, isolated colonies. This is essential for obtaining pure
cultures from mixed samples. Bacterial shapes: bacilli (rod-shaped), diplococci (paired spherical), tetrads (packets of four cocci), streptococci (chains),
staphylococci (clusters). Disinfectants are chemicals used on nonliving surfaces; antiseptics are safe for living tissue. Antimicrobial agents treat infections;
antibiotics specifically target bacteria.
5. Bactericidal and bacteriostatic drugs differ in that:
A. Bactericidal drugs inhibit growth; bacteriostatic drugs kill bacteria
B. Bactericidal drugs kill bacteria directly; bacteriostatic drugs inhibit bacterial growth without killing, relying on the host immune system to eliminate the pathogen
C. Both have identical mechanisms and clinical applications
D. Bacteriostatic drugs are only used for viral infections
CORRECT ANSWER B — Bactericidal drugs kill bacteria directly; bacteriostatic drugs inhibit growth without killing
RATIONALE Bactericidal drugs kill bacteria directly — they are preferred for life-threatening infections and immunocompromised patients. Bacteriostatic drugs inhibit
bacterial growth and reproduction without killing — the host immune system must eliminate the pathogen. This distinction guides clinical antibiotic selection.
Fermentation is the breakdown of carbohydrates producing acid and/or gas. Phenol red indicator: yellow broth = positive fermentation (acid produced); red broth
= negative fermentation; orange broth = weak fermentation requiring more incubation. A Durham tube traps gas produced during fermentation (bubble = gas
positive).
6. In a fermentation test, a yellow broth with a bubble in the Durham tube is recorded as:
A. A/- result — acid only, no gas
B. -/- result — no acid or gas (negative fermentation)
C. A/+ result — acid AND gas produced
D. Invalid result — the test must be repeated
CORRECT ANSWER C — A/+ result — acid AND gas produced
RATIONALE Fermentation results are recorded as: A/+ = acid produced (yellow broth) AND gas produced (bubble in Durham tube); A/- = acid only (yellow broth, no bubble); -/-
= no acid (red broth) or gas (negative fermentation). The phenol red indicator turns yellow when acid is produced (positive fermentation), remains red when no
acid is produced (negative fermentation), and appears orange when fermentation is weak and requires more incubation. The Durham tube is a small inverted tube
placed in the broth that traps any gas produced during fermentation — a visible bubble indicates gas production (+).
7. Immunoglobulins (antibodies) are Y-shaped proteins with specific functional regions. Which statement correctly pairs an antibody class with its function?
A. IgM — provides long-term immunity; can cross the placenta
B. IgG — provides long-term immunity and memory antibodies; the most abundant antibody in serum
C. IgA — B cell receptor; found on B cell surface
D. IgD — involved in allergies and parasitic infections
CORRECT ANSWER B — IgG provides long-term immunity and memory antibodies; most abundant in serum
RATIONALE The five immunoglobulin classes: IgG — long-term immunity, memory antibodies, crosses placenta, most abundant (~80%); IgM — first antibody produced in
response to antigen, pentamer (10 binding sites); IgA — found in body secretions (saliva, tears, breast milk, mucus), secretory antibody; IgE — involved in allergies
and parasitic (worm) infections; IgD — B cell receptor, found on B cell surface. All antibodies are Y-shaped with two antigen-binding sites (Fab regions) and an Fc
region that activates immune responses. An antigen is a substance that triggers an immune response; an epitope is the specific site on the antigen recognized by
the antibody.
8. The antibody-antigen interaction demonstrates specificity because:
A. Antibodies bind to any antigen they encounter indiscriminately
B. Each antibody binds only to its specific matching antigen at the epitope, like a lock and key; this enables neutralization of toxins and viruses
C. Antibodies are non-specific and work through general immune activation only
D. Specificity is only relevant for T cells, not antibodies
CORRECT ANSWER B — Antibodies bind only to specific matching antigens at the epitope; enables neutralization of toxins/viruses
RATIONALE Antibody specificity means each antibody binds only to its specific matching antigen at a particular epitope (the specific site on the antigen recognized by the
antibody). This lock-and-key interaction forms an antibody-antigen complex. Functional outcomes include: neutralization — antibodies block toxins or viruses
from binding to host cells. The Fab region is the antigen-binding region; the Fc region activates immune responses (complement activation, phagocyte binding).
This specificity is the basis for vaccines, diagnostic tests, and immunotherapy.
★ ★
Chamberlain University
C College of Nursing & Health Professions
J O U R N E Y T O E X T R A O R D I N A R Y CO M PA S S I O N AT E C A R E
EST. 1889
BIOS 242 — Lab Practicum Examination
M I C R O B I O LO G Y L A B O R ATO R Y T E C H N I Q U E S · M I C R O S CO P Y · STA I N I N G · I M M U N O LO G Y · S A F E TY
INSTITUTION Chamberlain University COURSE CODE BIOS 242
PROGRAM Bachelor of Science in Nursing (BSN) ACADEMIC YEAR
EXAM TITLE Lab Practicum — Microbiology Laboratory TOTAL QUESTIONS 25 Questions
COURSE TITLE Fundamentals of Microbiology FORMAT Multiple Choice — Select the Single Best Answer
LAB PR ACTICUM INSTRUCTIONS
▸ Select the single best answer for each question unless otherwise instructed.
▸ This practicum covers laboratory techniques, microscopy, Gram staining, fermentation testing, immunology, and aseptic technique.
▸ All content reflects BIOS 242 lab learning objectives.
▸ Correct answers and detailed rationales appear below each question for exam preparation purposes.
▸ Pay careful attention to Gram stain steps, fermentation results interpretation, and antibody structure/function.
SECTION I — LAB TECHNIQUES, MICROSCOPY, STAINING, FERMENTATION & IMMUNOLOGY Questions 1 – 25
1. Which culture method uses liquid nutrient media to grow bacteria?
A. Slant culture
B. Stab culture
C. Broth culture
D. Plate culture
CORRECT ANSWER C — Broth culture
RATIONALE Broth culture uses liquid nutrient media to grow bacteria — it provides a large surface area for bacterial growth in suspension. A slant culture is solid nutrient agar
solidified at an angle in a tube. A stab culture involves deep inoculation of nutrient agar using an inoculating needle. Sterile broth and sterile slant contain no
microorganisms. The inoculating loop is used to transfer bacteria across surfaces; the inoculating needle is used for stabbing or precise transfer. These tools are
sterilized using an incinerator before and after use.
2. Which microscope part controls the amount of light reaching the specimen?
A. Eyepiece lens — the lens you look through, usually 10x
B. Objective lenses — primary magnification lenses
C. Diaphragm or iris — adjusts light intensity
D. Arm — supports the microscope for carrying
CORRECT ANSWER C — Diaphragm or iris — adjusts light intensity
RATIONALE The diaphragm (or iris diaphragm) controls the amount of light reaching the specimen by adjusting the aperture. The condenser lens focuses light onto the
specimen. The eyepiece lens (ocular) is what you look through, typically 10x magnification. Objective lenses provide primary magnification (4x, 10x, 40x, 100x).
The stage holds the slide. The coarse adjustment knob moves the stage quickly for initial focus; the fine adjustment knob sharpens focus under high power. A
parfocal objective allows the microscope to stay approximately in focus when switching between lenses. The field of view is the visible area.
3. The correct sequence of steps in a Gram stain procedure is:
A. Safranin → Iodine → Decolorizer → Crystal Violet
B. Crystal Violet (primary stain) → Iodine (mordant) → Decolorizer (alcohol/acetone) → Safranin (counterstain)
C. Iodine → Crystal Violet → Safranin → Decolorizer
D. Decolorizer → Safranin → Crystal Violet → Iodine
CORRECT ANSWER B — Crystal Violet → Iodine → Decolorizer → Safranin
RATIONALE Gram stain procedure: (1) Crystal Violet — primary stain, colors ALL bacteria purple; (2) Iodine — mordant that fixes crystal violet in Gram-positive cells by forming
a crystal violet-iodine complex; (3) Decolorizer — alcohol or acetone that removes the stain from Gram-negative cells (which have a thin peptidoglycan layer and
outer membrane); (4) Safranin — counterstain that colors now-colorless Gram-negative bacteria pink. Gram-positive result: purple cells (thick peptidoglycan
retains crystal violet). Gram-negative result: pink cells (stain washed out, safranin taken up). A thin smear is heat-fixed to prepare bacteria for staining.
, 4. The purpose of the multi-stroke streak pattern is to:
A. Mix multiple bacterial species together in one plate
B. Separate bacteria to obtain pure, isolated colonies by progressively diluting the sample across the agar surface
C. Sterilize the agar surface before inoculation
D. Measure the growth rate of bacteria in liquid culture
CORRECT ANSWER B — Separate bacteria to obtain pure, isolated colonies by progressively diluting the sample
RATIONALE The multi-stroke streak pattern (quadrant streak) uses four sequential streaks to progressively dilute bacterial sample across the agar plate surface. Each streak
pulls fewer bacteria from the previous quadrant, eventually producing individual cells that multiply into pure, isolated colonies. This is essential for obtaining pure
cultures from mixed samples. Bacterial shapes: bacilli (rod-shaped), diplococci (paired spherical), tetrads (packets of four cocci), streptococci (chains),
staphylococci (clusters). Disinfectants are chemicals used on nonliving surfaces; antiseptics are safe for living tissue. Antimicrobial agents treat infections;
antibiotics specifically target bacteria.
5. Bactericidal and bacteriostatic drugs differ in that:
A. Bactericidal drugs inhibit growth; bacteriostatic drugs kill bacteria
B. Bactericidal drugs kill bacteria directly; bacteriostatic drugs inhibit bacterial growth without killing, relying on the host immune system to eliminate the pathogen
C. Both have identical mechanisms and clinical applications
D. Bacteriostatic drugs are only used for viral infections
CORRECT ANSWER B — Bactericidal drugs kill bacteria directly; bacteriostatic drugs inhibit growth without killing
RATIONALE Bactericidal drugs kill bacteria directly — they are preferred for life-threatening infections and immunocompromised patients. Bacteriostatic drugs inhibit
bacterial growth and reproduction without killing — the host immune system must eliminate the pathogen. This distinction guides clinical antibiotic selection.
Fermentation is the breakdown of carbohydrates producing acid and/or gas. Phenol red indicator: yellow broth = positive fermentation (acid produced); red broth
= negative fermentation; orange broth = weak fermentation requiring more incubation. A Durham tube traps gas produced during fermentation (bubble = gas
positive).
6. In a fermentation test, a yellow broth with a bubble in the Durham tube is recorded as:
A. A/- result — acid only, no gas
B. -/- result — no acid or gas (negative fermentation)
C. A/+ result — acid AND gas produced
D. Invalid result — the test must be repeated
CORRECT ANSWER C — A/+ result — acid AND gas produced
RATIONALE Fermentation results are recorded as: A/+ = acid produced (yellow broth) AND gas produced (bubble in Durham tube); A/- = acid only (yellow broth, no bubble); -/-
= no acid (red broth) or gas (negative fermentation). The phenol red indicator turns yellow when acid is produced (positive fermentation), remains red when no
acid is produced (negative fermentation), and appears orange when fermentation is weak and requires more incubation. The Durham tube is a small inverted tube
placed in the broth that traps any gas produced during fermentation — a visible bubble indicates gas production (+).
7. Immunoglobulins (antibodies) are Y-shaped proteins with specific functional regions. Which statement correctly pairs an antibody class with its function?
A. IgM — provides long-term immunity; can cross the placenta
B. IgG — provides long-term immunity and memory antibodies; the most abundant antibody in serum
C. IgA — B cell receptor; found on B cell surface
D. IgD — involved in allergies and parasitic infections
CORRECT ANSWER B — IgG provides long-term immunity and memory antibodies; most abundant in serum
RATIONALE The five immunoglobulin classes: IgG — long-term immunity, memory antibodies, crosses placenta, most abundant (~80%); IgM — first antibody produced in
response to antigen, pentamer (10 binding sites); IgA — found in body secretions (saliva, tears, breast milk, mucus), secretory antibody; IgE — involved in allergies
and parasitic (worm) infections; IgD — B cell receptor, found on B cell surface. All antibodies are Y-shaped with two antigen-binding sites (Fab regions) and an Fc
region that activates immune responses. An antigen is a substance that triggers an immune response; an epitope is the specific site on the antigen recognized by
the antibody.
8. The antibody-antigen interaction demonstrates specificity because:
A. Antibodies bind to any antigen they encounter indiscriminately
B. Each antibody binds only to its specific matching antigen at the epitope, like a lock and key; this enables neutralization of toxins and viruses
C. Antibodies are non-specific and work through general immune activation only
D. Specificity is only relevant for T cells, not antibodies
CORRECT ANSWER B — Antibodies bind only to specific matching antigens at the epitope; enables neutralization of toxins/viruses
RATIONALE Antibody specificity means each antibody binds only to its specific matching antigen at a particular epitope (the specific site on the antigen recognized by the
antibody). This lock-and-key interaction forms an antibody-antigen complex. Functional outcomes include: neutralization — antibodies block toxins or viruses
from binding to host cells. The Fab region is the antigen-binding region; the Fc region activates immune responses (complement activation, phagocyte binding).
This specificity is the basis for vaccines, diagnostic tests, and immunotherapy.
