,BIOD 101 Module 6 | Essential Biology I | Portage Learning |
Questions & Verified Answers | 2026 Edition
1. Which of the following best describes the location of DNA in a prokaryotic cell?
A) DNA is housed within a membrane-bound nucleus
B) DNA is located in a nucleoid region that is not membrane-bound
C) DNA is found within the mitochondria
D) DNA is dispersed throughout the cytoplasm without any organized region
Correct Answer: DNA is located in a nucleoid region that is not membrane-bound
Rationale: Prokaryotic cells store their genetic material in a nucleoid region, which is not enclosed by a
membrane. Eukaryotic cells, by contrast, house their DNA within a membrane-bound nucleus. This
structural difference is a fundamental distinction between the two cell types.
2. What is the primary function of plasmids in bacteria?
A) To store the main chromosomal DNA of the cell
B) To serve as small, circular regions of DNA that carry accessory genes
C) To synthesize proteins for cellular metabolism
D) To provide structural support to the cell wall
Correct Answer: To serve as small, circular regions of DNA that carry accessory genes
Rationale: Plasmids are small, circular DNA molecules found in bacteria that carry accessory genes
separate from the main chromosome. They often contain genes for antibiotic resistance or other
beneficial traits and can be transferred between bacteria.
3. Which structure is responsible for the rigid shape and protection of a bacterial cell?
A) Plasma membrane
B) Capsule
C) Cell wall
,D) Fimbriae
Correct Answer: Cell wall
Rationale: The cell wall is a rigid structure surrounding the plasma membrane that is responsible for the
shape of the cell and provides protection against environmental stressors. In bacteria, the cell wall is
composed of peptidoglycan.
4. What is peptidoglycan?
A) A lipid layer found only in Gram-negative bacteria
B) A polymer consisting of two cross-linked sugars, NAG and NAM
C) A protein structure that forms bacterial flagella
D) A carbohydrate storage molecule in bacterial cells
Correct Answer: A polymer consisting of two cross-linked sugars, NAG and NAM
Rationale: Peptidoglycan is a polymer composed of two cross-linked sugars: N-acetylglucosamine (NAG)
and N-acetylmuric acid (NAM). It forms the rigid cell wall of bacteria and is the target of many
antibiotics, such as penicillin.
5. How do Gram-positive and Gram-negative bacteria differ in their cell wall structure?
A) Gram-positive bacteria have a thin peptidoglycan layer; Gram-negative bacteria have a thick
peptidoglycan layer
B) Gram-positive bacteria have a thick peptidoglycan layer; Gram-negative bacteria have a thin
peptidoglycan layer surrounded by an outer membrane
C) Both have identical cell wall structures
D) Gram-positive bacteria lack peptidoglycan entirely
Correct Answer: Gram-positive bacteria have a thick peptidoglycan layer; Gram-negative bacteria have a
thin peptidoglycan layer surrounded by an outer membrane
, Rationale: Gram-positive bacteria possess a thick layer of peptidoglycan. Gram-negative bacteria have a
thin peptidoglycan layer surrounded by an additional outer membrane made of lipopolysaccharides.
This structural difference is the basis for the Gram-stain procedure.
6. During the Gram-stain procedure, what color do Gram-positive bacteria appear?
A) Pink or red
B) Purple
C) Green
D) Colorless
Correct Answer: Purple
Rationale: During the Gram-stain procedure, Gram-positive bacteria retain the crystal violet dye and
appear purple. Gram-negative bacteria do not retain the crystal violet and appear pink or red after the
counterstain.
7. During the Gram-stain procedure, what color do Gram-negative bacteria appear?
A) Purple
B) Blue
C) Pink or red
D) Yellow
Correct Answer: Pink or red
Rationale: Gram-negative bacteria have a thin peptidoglycan layer and an outer membrane that does
not retain the crystal violet dye. After the alcohol rinse and application of the red counterstain, they
appear pink or red.
8. What are the three most common bacterial shapes?
A) Spherical, rod, and spiral
B) Circular, oval, and triangular
Questions & Verified Answers | 2026 Edition
1. Which of the following best describes the location of DNA in a prokaryotic cell?
A) DNA is housed within a membrane-bound nucleus
B) DNA is located in a nucleoid region that is not membrane-bound
C) DNA is found within the mitochondria
D) DNA is dispersed throughout the cytoplasm without any organized region
Correct Answer: DNA is located in a nucleoid region that is not membrane-bound
Rationale: Prokaryotic cells store their genetic material in a nucleoid region, which is not enclosed by a
membrane. Eukaryotic cells, by contrast, house their DNA within a membrane-bound nucleus. This
structural difference is a fundamental distinction between the two cell types.
2. What is the primary function of plasmids in bacteria?
A) To store the main chromosomal DNA of the cell
B) To serve as small, circular regions of DNA that carry accessory genes
C) To synthesize proteins for cellular metabolism
D) To provide structural support to the cell wall
Correct Answer: To serve as small, circular regions of DNA that carry accessory genes
Rationale: Plasmids are small, circular DNA molecules found in bacteria that carry accessory genes
separate from the main chromosome. They often contain genes for antibiotic resistance or other
beneficial traits and can be transferred between bacteria.
3. Which structure is responsible for the rigid shape and protection of a bacterial cell?
A) Plasma membrane
B) Capsule
C) Cell wall
,D) Fimbriae
Correct Answer: Cell wall
Rationale: The cell wall is a rigid structure surrounding the plasma membrane that is responsible for the
shape of the cell and provides protection against environmental stressors. In bacteria, the cell wall is
composed of peptidoglycan.
4. What is peptidoglycan?
A) A lipid layer found only in Gram-negative bacteria
B) A polymer consisting of two cross-linked sugars, NAG and NAM
C) A protein structure that forms bacterial flagella
D) A carbohydrate storage molecule in bacterial cells
Correct Answer: A polymer consisting of two cross-linked sugars, NAG and NAM
Rationale: Peptidoglycan is a polymer composed of two cross-linked sugars: N-acetylglucosamine (NAG)
and N-acetylmuric acid (NAM). It forms the rigid cell wall of bacteria and is the target of many
antibiotics, such as penicillin.
5. How do Gram-positive and Gram-negative bacteria differ in their cell wall structure?
A) Gram-positive bacteria have a thin peptidoglycan layer; Gram-negative bacteria have a thick
peptidoglycan layer
B) Gram-positive bacteria have a thick peptidoglycan layer; Gram-negative bacteria have a thin
peptidoglycan layer surrounded by an outer membrane
C) Both have identical cell wall structures
D) Gram-positive bacteria lack peptidoglycan entirely
Correct Answer: Gram-positive bacteria have a thick peptidoglycan layer; Gram-negative bacteria have a
thin peptidoglycan layer surrounded by an outer membrane
, Rationale: Gram-positive bacteria possess a thick layer of peptidoglycan. Gram-negative bacteria have a
thin peptidoglycan layer surrounded by an additional outer membrane made of lipopolysaccharides.
This structural difference is the basis for the Gram-stain procedure.
6. During the Gram-stain procedure, what color do Gram-positive bacteria appear?
A) Pink or red
B) Purple
C) Green
D) Colorless
Correct Answer: Purple
Rationale: During the Gram-stain procedure, Gram-positive bacteria retain the crystal violet dye and
appear purple. Gram-negative bacteria do not retain the crystal violet and appear pink or red after the
counterstain.
7. During the Gram-stain procedure, what color do Gram-negative bacteria appear?
A) Purple
B) Blue
C) Pink or red
D) Yellow
Correct Answer: Pink or red
Rationale: Gram-negative bacteria have a thin peptidoglycan layer and an outer membrane that does
not retain the crystal violet dye. After the alcohol rinse and application of the red counterstain, they
appear pink or red.
8. What are the three most common bacterial shapes?
A) Spherical, rod, and spiral
B) Circular, oval, and triangular
