BIOL180 Unit Test 2 Cell Structure
and Function Questions And Correct
Answers (Verified Answers) Plus
Rationales 2026 Q&A | Instant
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1. Which statement best describes the cell theory?
A. All organisms are composed only of tissues.
B. Cells arise spontaneously from nonliving matter.
C. Only multicellular organisms are made of cells.
D. All living organisms are composed of one or more cells, and cells
are the basic unit of life.
Answer: D. All living organisms are composed of one or more cells,
and cells are the basic unit of life.
Rationale: Cell theory establishes that the cell is the fundamental
structural and functional unit of living organisms. It also states that
new cells arise from preexisting cells. Unicellular organisms consist of
a single cell, whereas multicellular organisms contain many
specialized cells. The other choices incorrectly exclude unicellular
organisms or describe outdated ideas about spontaneous generation.
2. Which feature is characteristic of prokaryotic cells but not
eukaryotic cells?
A. A region containing DNA that is not enclosed by a membrane-
bound nucleus
B. Membrane-bound mitochondria
,C. A membrane-bound nucleus
D. An endoplasmic reticulum
Answer: A. A region containing DNA that is not enclosed by a
membrane-bound nucleus
Rationale: Prokaryotic cells, including bacteria and archaea, lack a
membrane-bound nucleus. Their DNA is located in a nucleoid region.
Eukaryotic cells possess a nucleus surrounded by a nuclear envelope.
Prokaryotes also lack membrane-bound organelles such as
mitochondria and endoplasmic reticulum.
3. What is the primary advantage of compartmentalization in
eukaryotic cells?
A. It prevents all chemical reactions from occurring simultaneously.
B. It eliminates the need for enzymes.
C. It allows different cellular processes to occur in specialized
environments.
D. It prevents molecules from moving within the cell.
Answer: C. It allows different cellular processes to occur in specialized
environments.
Rationale: Membrane-bound organelles create distinct environments
where particular biochemical reactions can occur efficiently. For
example, lysosomes provide an acidic environment for digestion, while
mitochondria provide specialized compartments for cellular
respiration. Compartmentalization increases organization and allows
incompatible processes to occur separately.
4. Which structure controls the movement of substances into and out
of a cell?
,A. Ribosome
B. Plasma membrane
C. Nucleolus
D. Cytoskeleton
Answer: B. Plasma membrane
Rationale: The plasma membrane forms the boundary between the cell
and its external environment and regulates the movement of ions,
nutrients, wastes, and other substances. Its selective permeability
allows the cell to maintain internal conditions different from those
outside the cell. Ribosomes synthesize proteins, the nucleolus produces
ribosomal components, and the cytoskeleton provides structural
support and intracellular organization.
5. Which molecules are the primary structural components of the
plasma membrane?
A. DNA and RNA
B. Proteins and carbohydrates only
C. Cholesterol and nucleic acids
D. Phospholipids and proteins
Answer: D. Phospholipids and proteins
Rationale: The plasma membrane consists primarily of a phospholipid
bilayer containing many proteins. Phospholipids create the
membrane's basic structural framework, while proteins perform
functions such as transport, signaling, enzymatic activity, and cell
adhesion. Cholesterol is also an important membrane component in
animal cells, but it is not the primary structural framework.
6. Why are phospholipids described as amphipathic molecules?
, A. They contain only hydrophobic regions.
B. They contain only hydrophilic regions.
C. They contain both hydrophilic and hydrophobic regions.
D. They can dissolve equally well in water and oil.
Answer: C. They contain both hydrophilic and hydrophobic regions.
Rationale: A phospholipid has a polar, hydrophilic phosphate-
containing head and nonpolar, hydrophobic fatty acid tails. In an
aqueous environment, the heads interact with water while the tails
avoid water. This property causes phospholipids to spontaneously
organize into a bilayer, forming the foundation of biological
membranes.
7. What happens to phospholipids when placed in an aqueous
environment?
A. They tend to arrange themselves into structures with hydrophilic
heads facing water and hydrophobic tails away from water.
B. Their fatty acid tails dissolve completely in water.
C. Their phosphate groups move away from water.
D. They form covalent bonds with water molecules.
Answer: A. They tend to arrange themselves into structures with
hydrophilic heads facing water and hydrophobic tails away from
water.
Rationale: The hydrophobic effect drives phospholipids to arrange so
that their nonpolar tails are shielded from water while their polar
heads remain exposed to the aqueous environment. In cells, this
produces a phospholipid bilayer. This organization is fundamental to
the structure and selective permeability of biological membranes.
and Function Questions And Correct
Answers (Verified Answers) Plus
Rationales 2026 Q&A | Instant
Download Pdf
1. Which statement best describes the cell theory?
A. All organisms are composed only of tissues.
B. Cells arise spontaneously from nonliving matter.
C. Only multicellular organisms are made of cells.
D. All living organisms are composed of one or more cells, and cells
are the basic unit of life.
Answer: D. All living organisms are composed of one or more cells,
and cells are the basic unit of life.
Rationale: Cell theory establishes that the cell is the fundamental
structural and functional unit of living organisms. It also states that
new cells arise from preexisting cells. Unicellular organisms consist of
a single cell, whereas multicellular organisms contain many
specialized cells. The other choices incorrectly exclude unicellular
organisms or describe outdated ideas about spontaneous generation.
2. Which feature is characteristic of prokaryotic cells but not
eukaryotic cells?
A. A region containing DNA that is not enclosed by a membrane-
bound nucleus
B. Membrane-bound mitochondria
,C. A membrane-bound nucleus
D. An endoplasmic reticulum
Answer: A. A region containing DNA that is not enclosed by a
membrane-bound nucleus
Rationale: Prokaryotic cells, including bacteria and archaea, lack a
membrane-bound nucleus. Their DNA is located in a nucleoid region.
Eukaryotic cells possess a nucleus surrounded by a nuclear envelope.
Prokaryotes also lack membrane-bound organelles such as
mitochondria and endoplasmic reticulum.
3. What is the primary advantage of compartmentalization in
eukaryotic cells?
A. It prevents all chemical reactions from occurring simultaneously.
B. It eliminates the need for enzymes.
C. It allows different cellular processes to occur in specialized
environments.
D. It prevents molecules from moving within the cell.
Answer: C. It allows different cellular processes to occur in specialized
environments.
Rationale: Membrane-bound organelles create distinct environments
where particular biochemical reactions can occur efficiently. For
example, lysosomes provide an acidic environment for digestion, while
mitochondria provide specialized compartments for cellular
respiration. Compartmentalization increases organization and allows
incompatible processes to occur separately.
4. Which structure controls the movement of substances into and out
of a cell?
,A. Ribosome
B. Plasma membrane
C. Nucleolus
D. Cytoskeleton
Answer: B. Plasma membrane
Rationale: The plasma membrane forms the boundary between the cell
and its external environment and regulates the movement of ions,
nutrients, wastes, and other substances. Its selective permeability
allows the cell to maintain internal conditions different from those
outside the cell. Ribosomes synthesize proteins, the nucleolus produces
ribosomal components, and the cytoskeleton provides structural
support and intracellular organization.
5. Which molecules are the primary structural components of the
plasma membrane?
A. DNA and RNA
B. Proteins and carbohydrates only
C. Cholesterol and nucleic acids
D. Phospholipids and proteins
Answer: D. Phospholipids and proteins
Rationale: The plasma membrane consists primarily of a phospholipid
bilayer containing many proteins. Phospholipids create the
membrane's basic structural framework, while proteins perform
functions such as transport, signaling, enzymatic activity, and cell
adhesion. Cholesterol is also an important membrane component in
animal cells, but it is not the primary structural framework.
6. Why are phospholipids described as amphipathic molecules?
, A. They contain only hydrophobic regions.
B. They contain only hydrophilic regions.
C. They contain both hydrophilic and hydrophobic regions.
D. They can dissolve equally well in water and oil.
Answer: C. They contain both hydrophilic and hydrophobic regions.
Rationale: A phospholipid has a polar, hydrophilic phosphate-
containing head and nonpolar, hydrophobic fatty acid tails. In an
aqueous environment, the heads interact with water while the tails
avoid water. This property causes phospholipids to spontaneously
organize into a bilayer, forming the foundation of biological
membranes.
7. What happens to phospholipids when placed in an aqueous
environment?
A. They tend to arrange themselves into structures with hydrophilic
heads facing water and hydrophobic tails away from water.
B. Their fatty acid tails dissolve completely in water.
C. Their phosphate groups move away from water.
D. They form covalent bonds with water molecules.
Answer: A. They tend to arrange themselves into structures with
hydrophilic heads facing water and hydrophobic tails away from
water.
Rationale: The hydrophobic effect drives phospholipids to arrange so
that their nonpolar tails are shielded from water while their polar
heads remain exposed to the aqueous environment. In cells, this
produces a phospholipid bilayer. This organization is fundamental to
the structure and selective permeability of biological membranes.
