BIOD 171 Module 4: Exam Portage Learning Questions and
Answers 2026 Practice Set
1. Which of the following is the smallest biological unit of life?
A) Atom
B) Molecule
C) Cell
D) Organelle
Rationale: The cell is the simplest structure capable of performing all functions of life.
2. Viruses are classified as _____ but not as _____.
A) Microbes; microorganisms
B) Microorganisms; microbes
C) Prokaryotes; eukaryotes
D) Eukaryotes; prokaryotes
Rationale: Viruses are microbes (microscopic), but because they are non-living, they
are not organisms.
3. Which macromolecule is a polymer of 20 different amino acids?
A) Lipid
B) Carbohydrate
C) Protein
D) Nucleic Acid
Rationale: Proteins are built from a universal set of 20 amino acids.
4. The "hydrophobic" portion of the plasma membrane is composed of:
A) Sugar chains
B) Lipid tails
C) Protein channels
D) Nucleic acids
Rationale: The fatty acid tails of phospholipids repel water, creating the internal barrier
of the membrane.
5. Which organelle is responsible for the synthesis of ATP?
A) Ribosome
B) Golgi complex
C) Mitochondria
D) Lysosome
Rationale: Mitochondria perform cellular respiration to produce energy (ATP).
,6. Prokaryotic DNA is found in a region called the:
A) Nucleus
B) Nucleoid
C) Plasmid
D) Ribosome
Rationale: Prokaryotes lack a membrane-bound nucleus; their DNA clusters in the
nucleoid.
7. Which of the following is a "differential" stain?
A) Methylene Blue
B) Gram Stain
C) Crystal Violet
D) India Ink
Rationale: A differential stain uses multiple dyes to distinguish between different types
of cells (e.g., Gram-positive vs. Gram-negative).
8. What is the total magnification of a 10x ocular and a 40x objective?
A) 40x
B) 50x
C) 400x
D) 4000x
Rationale: Total magnification = Ocular × Objective (10 × 40 = 400).
9. In a Gram stain, Gram-positive bacteria appear _____ after the procedure.
A) Pink
B) Purple
C) Colorless
D) Green
Rationale: Gram-positive cells retain the primary Crystal Violet dye due to their thick
peptidoglycan layer.
10. What is the "mordant" in the Gram stain process?
A) Crystal Violet
B) Iodine
C) Alcohol
D) Safranin
Rationale: Iodine forms a complex with Crystal Violet to "trap" it inside the cell wall.
11. Which microscope is best for viewing internal structures of a dead, sliced
specimen?
A) Transmission Electron (TEM)
,B) Scanning Electron (SEM)
C) Phase-contrast
D) Bright-field
Rationale: TEM passes electrons through thin slices to show internal ultra-structure.
12. "Acid-fast" staining is specifically used to identify which genus?
A) Staphylococcus
B) Escherichia
C) Mycobacterium
D) Bacillus
Rationale: Mycobacterium (TB/Leprosy) have waxy mycolic acids that require acid-fast
staining.
13. A spherical-shaped bacterium is called a:
A) Coccus
B) Bacillus
C) Spirillum
D) Vibrio
Rationale: Cocci are round; bacilli are rods.
14. What is the primary purpose of a "Quadrant Streak"?
A) To kill bacteria
B) To obtain isolated colonies
C) To test for antibiotic resistance
D) To measure growth rate
Rationale: Streaking dilutes the sample until individual cells grow into separate, pure
colonies.
15. Which phase of the growth curve shows the most rapid cell division?
A) Lag phase
B) Log phase
C) Stationary phase
D) Death phase
Rationale: During the Log (exponential) phase, the population doubles at a constant
rate.
16. An organism that thrives at human body temperature (
) is a:
A) Psychrophile
B) Mesophile
, C) Thermophile
D) Halophile
Rationale: Mesophiles prefer moderate temperatures (20–45°C).
17. "Enzymes" speed up reactions by:
A) Increasing temperature
B) Lowering activation energy
C) Adding ATP
D) Changing the product
Rationale: Enzymes are catalysts that reduce the energy required to start a reaction.
18. Glycolysis breaks down one glucose into two molecules of:
A) Acetyl-CoA
B) Citrate
C) Pyruvate
D) Lactate
Rationale: Glycolysis is the splitting of sugar into two 3-carbon pyruvates.
19. What is the "energy currency" produced during the Electron Transport Chain?
A) NADH
B) Glucose
C) ATP
D) FADH2
Rationale: ATP is the final energy product of oxidative phosphorylation.
20. In the absence of oxygen, pyruvate can be converted to lactic acid via:
A) The TCA cycle
B) Fermentation
C) Chemiosmosis
D) Beta-oxidation
Rationale: Fermentation allows for energy production without oxygen by recycling
NAD+.
21. Blood Agar is used to detect _____, the lysis of red blood cells.
A) Fermentation
B) Hemolysis
C) Oxidation
D) Nitrogen fixation
Rationale: Hemolysis patterns (alpha, beta, gamma) are diagnostic on Blood Agar.
22. Which media is "Selective" for Gram-negative and "Differential" for lactose?
A) Blood Agar
Answers 2026 Practice Set
1. Which of the following is the smallest biological unit of life?
A) Atom
B) Molecule
C) Cell
D) Organelle
Rationale: The cell is the simplest structure capable of performing all functions of life.
2. Viruses are classified as _____ but not as _____.
A) Microbes; microorganisms
B) Microorganisms; microbes
C) Prokaryotes; eukaryotes
D) Eukaryotes; prokaryotes
Rationale: Viruses are microbes (microscopic), but because they are non-living, they
are not organisms.
3. Which macromolecule is a polymer of 20 different amino acids?
A) Lipid
B) Carbohydrate
C) Protein
D) Nucleic Acid
Rationale: Proteins are built from a universal set of 20 amino acids.
4. The "hydrophobic" portion of the plasma membrane is composed of:
A) Sugar chains
B) Lipid tails
C) Protein channels
D) Nucleic acids
Rationale: The fatty acid tails of phospholipids repel water, creating the internal barrier
of the membrane.
5. Which organelle is responsible for the synthesis of ATP?
A) Ribosome
B) Golgi complex
C) Mitochondria
D) Lysosome
Rationale: Mitochondria perform cellular respiration to produce energy (ATP).
,6. Prokaryotic DNA is found in a region called the:
A) Nucleus
B) Nucleoid
C) Plasmid
D) Ribosome
Rationale: Prokaryotes lack a membrane-bound nucleus; their DNA clusters in the
nucleoid.
7. Which of the following is a "differential" stain?
A) Methylene Blue
B) Gram Stain
C) Crystal Violet
D) India Ink
Rationale: A differential stain uses multiple dyes to distinguish between different types
of cells (e.g., Gram-positive vs. Gram-negative).
8. What is the total magnification of a 10x ocular and a 40x objective?
A) 40x
B) 50x
C) 400x
D) 4000x
Rationale: Total magnification = Ocular × Objective (10 × 40 = 400).
9. In a Gram stain, Gram-positive bacteria appear _____ after the procedure.
A) Pink
B) Purple
C) Colorless
D) Green
Rationale: Gram-positive cells retain the primary Crystal Violet dye due to their thick
peptidoglycan layer.
10. What is the "mordant" in the Gram stain process?
A) Crystal Violet
B) Iodine
C) Alcohol
D) Safranin
Rationale: Iodine forms a complex with Crystal Violet to "trap" it inside the cell wall.
11. Which microscope is best for viewing internal structures of a dead, sliced
specimen?
A) Transmission Electron (TEM)
,B) Scanning Electron (SEM)
C) Phase-contrast
D) Bright-field
Rationale: TEM passes electrons through thin slices to show internal ultra-structure.
12. "Acid-fast" staining is specifically used to identify which genus?
A) Staphylococcus
B) Escherichia
C) Mycobacterium
D) Bacillus
Rationale: Mycobacterium (TB/Leprosy) have waxy mycolic acids that require acid-fast
staining.
13. A spherical-shaped bacterium is called a:
A) Coccus
B) Bacillus
C) Spirillum
D) Vibrio
Rationale: Cocci are round; bacilli are rods.
14. What is the primary purpose of a "Quadrant Streak"?
A) To kill bacteria
B) To obtain isolated colonies
C) To test for antibiotic resistance
D) To measure growth rate
Rationale: Streaking dilutes the sample until individual cells grow into separate, pure
colonies.
15. Which phase of the growth curve shows the most rapid cell division?
A) Lag phase
B) Log phase
C) Stationary phase
D) Death phase
Rationale: During the Log (exponential) phase, the population doubles at a constant
rate.
16. An organism that thrives at human body temperature (
) is a:
A) Psychrophile
B) Mesophile
, C) Thermophile
D) Halophile
Rationale: Mesophiles prefer moderate temperatures (20–45°C).
17. "Enzymes" speed up reactions by:
A) Increasing temperature
B) Lowering activation energy
C) Adding ATP
D) Changing the product
Rationale: Enzymes are catalysts that reduce the energy required to start a reaction.
18. Glycolysis breaks down one glucose into two molecules of:
A) Acetyl-CoA
B) Citrate
C) Pyruvate
D) Lactate
Rationale: Glycolysis is the splitting of sugar into two 3-carbon pyruvates.
19. What is the "energy currency" produced during the Electron Transport Chain?
A) NADH
B) Glucose
C) ATP
D) FADH2
Rationale: ATP is the final energy product of oxidative phosphorylation.
20. In the absence of oxygen, pyruvate can be converted to lactic acid via:
A) The TCA cycle
B) Fermentation
C) Chemiosmosis
D) Beta-oxidation
Rationale: Fermentation allows for energy production without oxygen by recycling
NAD+.
21. Blood Agar is used to detect _____, the lysis of red blood cells.
A) Fermentation
B) Hemolysis
C) Oxidation
D) Nitrogen fixation
Rationale: Hemolysis patterns (alpha, beta, gamma) are diagnostic on Blood Agar.
22. Which media is "Selective" for Gram-negative and "Differential" for lactose?
A) Blood Agar
