Portage Learning / Geneva
3 MAXE · 171 DOIB
GENEVA
College
COLLEGE
G
Department of Natural Sciences
EST. 1848
P R O C H R I S T O E T P AT R I A
BIOD 171 Portage Learning Exam 3
E SS E N T I A L L A B M I C R O B I O LO G Y — M I C R O S CO PY A N D STA I N I N G
INSTITUTION Portage Learning / Geneva College COURSE CODE BIOD 171
PROGRAM Pre-Nursing / Health Sciences ACADEMIC YEAR
EXAM TITLE BIOD 171 Portage Learning Exam 3 TOTAL QUESTIONS 52 Questions
COURSE TITLE Essential Lab Microbiology FORMAT Multiple Choice — Select the
Single Best Answer
EXAMINATION INSTRUCTIONS
▸ Select the single best answer for each question.
▸ Content covers microscopy, staining techniques, Gram classification, and diagnostic microbiology.
▸ Correct answers and detailed rationales appear below each question.
, SECTION I — BIOD 171: MICROSCOPY AND STAINING —
Questions 1 – 52
EXAM 3
1. Define the measurements micrometer and nanometer.
A. Micrometer = 10⁻³ m; Nanometer = 10⁻⁶ m
B. Micrometer = one-millionth of a meter (10⁻⁶); Nanometer = one-billionth of a meter (10⁻⁹)
C. Both equal 10⁻⁹ m
D. Micrometer = 10⁻⁹ m; Nanometer = 10⁻¹² m
CORRECT ANSWER B — Micrometer (µm) = 10⁻⁶ m; Nanometer (nm) = 10⁻⁹ m
RATIONALE A micrometer is one-millionth (10⁻⁶) of a meter — bacteria are typically 1-10 µm. A
nanometer is one-billionth (10⁻⁹) of a meter — viruses are typically 30-150 nm. A
nanometer is 1,000 times smaller than a micrometer. These measurements are
fundamental to understanding scale in microbiology.
2. What are the two critical factors that influence your ability to see an object under a
microscope?
A. Magnification and color
B. Resolution and contrast
C. Temperature and pressure
D. Weight and density
CORRECT ANSWER B — Resolution and contrast
RATIONALE Resolution: the minimum distance between two objects at which they can still be
seen as separate (poor resolution = objects blur together). Contrast: the difference
in light absorbance between two objects (poor contrast = high background
making visualization difficult). These are far more important than magnification
alone — high magnification with poor resolution produces a large, blurry image.
, 3. If you wish to increase the amount of light going into a microscope, what part would you
adjust?
A. Objective lens
B. Ocular lens
C. Iris diaphragm
D. Stage
CORRECT ANSWER C — Iris diaphragm
RATIONALE The iris diaphragm is located beneath the stage and controls the diameter of the
light beam. Opening it increases light; closing it decreases light. The objective
lens magnifies. The ocular lens is the eyepiece. The stage holds the slide. The iris
diaphragm is the primary control for light intensity.
4. As light passes through a microscope, what is the last piece that light passes through
before reaching your eyes?
A. Objective lens
B. Condenser
C. Ocular lens (eyepiece)
D. Stage
CORRECT ANSWER C — Ocular lens (eyepiece)
RATIONALE Light path: source → condenser → specimen on stage → objective lens (primary
magnification) → body tube → ocular lens/eyepiece (secondary magnification)
→ eye. The ocular lens is the final optical element before your eye.
3 MAXE · 171 DOIB
GENEVA
College
COLLEGE
G
Department of Natural Sciences
EST. 1848
P R O C H R I S T O E T P AT R I A
BIOD 171 Portage Learning Exam 3
E SS E N T I A L L A B M I C R O B I O LO G Y — M I C R O S CO PY A N D STA I N I N G
INSTITUTION Portage Learning / Geneva College COURSE CODE BIOD 171
PROGRAM Pre-Nursing / Health Sciences ACADEMIC YEAR
EXAM TITLE BIOD 171 Portage Learning Exam 3 TOTAL QUESTIONS 52 Questions
COURSE TITLE Essential Lab Microbiology FORMAT Multiple Choice — Select the
Single Best Answer
EXAMINATION INSTRUCTIONS
▸ Select the single best answer for each question.
▸ Content covers microscopy, staining techniques, Gram classification, and diagnostic microbiology.
▸ Correct answers and detailed rationales appear below each question.
, SECTION I — BIOD 171: MICROSCOPY AND STAINING —
Questions 1 – 52
EXAM 3
1. Define the measurements micrometer and nanometer.
A. Micrometer = 10⁻³ m; Nanometer = 10⁻⁶ m
B. Micrometer = one-millionth of a meter (10⁻⁶); Nanometer = one-billionth of a meter (10⁻⁹)
C. Both equal 10⁻⁹ m
D. Micrometer = 10⁻⁹ m; Nanometer = 10⁻¹² m
CORRECT ANSWER B — Micrometer (µm) = 10⁻⁶ m; Nanometer (nm) = 10⁻⁹ m
RATIONALE A micrometer is one-millionth (10⁻⁶) of a meter — bacteria are typically 1-10 µm. A
nanometer is one-billionth (10⁻⁹) of a meter — viruses are typically 30-150 nm. A
nanometer is 1,000 times smaller than a micrometer. These measurements are
fundamental to understanding scale in microbiology.
2. What are the two critical factors that influence your ability to see an object under a
microscope?
A. Magnification and color
B. Resolution and contrast
C. Temperature and pressure
D. Weight and density
CORRECT ANSWER B — Resolution and contrast
RATIONALE Resolution: the minimum distance between two objects at which they can still be
seen as separate (poor resolution = objects blur together). Contrast: the difference
in light absorbance between two objects (poor contrast = high background
making visualization difficult). These are far more important than magnification
alone — high magnification with poor resolution produces a large, blurry image.
, 3. If you wish to increase the amount of light going into a microscope, what part would you
adjust?
A. Objective lens
B. Ocular lens
C. Iris diaphragm
D. Stage
CORRECT ANSWER C — Iris diaphragm
RATIONALE The iris diaphragm is located beneath the stage and controls the diameter of the
light beam. Opening it increases light; closing it decreases light. The objective
lens magnifies. The ocular lens is the eyepiece. The stage holds the slide. The iris
diaphragm is the primary control for light intensity.
4. As light passes through a microscope, what is the last piece that light passes through
before reaching your eyes?
A. Objective lens
B. Condenser
C. Ocular lens (eyepiece)
D. Stage
CORRECT ANSWER C — Ocular lens (eyepiece)
RATIONALE Light path: source → condenser → specimen on stage → objective lens (primary
magnification) → body tube → ocular lens/eyepiece (secondary magnification)
→ eye. The ocular lens is the final optical element before your eye.
