Quiz: Cell Structure and Function — 20 questions

1. What is the defining status of a human cell in living tissue?

A. It is a genetic storage structure surrounded by specialized organelles

B. It is the basic structural and functional unit, and it is eukaryotic

C. It is a specialized component that operates within a larger cellular unit

D. It is a transport compartment that supports the activity of neighboring cells

Answer: (B)

Explanation

A human cell is the basic structural and functional unit of living tissues and is eukaryotic. An organelle is instead a specialized component within the cell, not the complete cellular unit.

2. Which three structures constitute the major components of a human cell?

A. The phospholipid bilayer, ribosomes, and peroxisomes

B. The plasma membrane, cytoplasm, and nucleus

C. The cytoskeleton, lysosomes, and mitochondria

D. The nucleolus, Golgi apparatus, and cytosol

Answer: (B)

Explanation

The major components of a human cell are the plasma membrane, cytoplasm, and nucleus. The other choices list organelles or cellular structures rather than the three major components.

3. What distinguishes a single-membrane-bound organelle from a double-membrane-bound organelle?

A. The location of the organelle within the cytoplasm

B. The number of membranes surrounding the organelle

C. The presence of genetic material inside the organelle

D. The ability of the organelle to synthesize cellular proteins

Answer: (B)

Explanation

The classification depends on whether an organelle has one surrounding membrane or two. Genetic material, location, and protein synthesis do not define this membrane-based distinction.

4. Which pairing correctly classifies the listed organelles by membrane arrangement?

A. Centrioles are double-membrane-bound, whereas the Golgi apparatus is non-membrane-bound

B. Lysosomes are single-membrane-bound, whereas mitochondria are double-membrane-bound

C. The nucleus is single-membrane-bound, whereas peroxisomes are double-membrane-bound

D. Ribosomes are single-membrane-bound, whereas vesicles are double-membrane-bound

Answer: (B)

Explanation

Lysosomes have a single surrounding membrane, while mitochondria have two surrounding membranes. Ribosomes and centrioles lack surrounding membranes, and the nucleus is double-membrane-bound.

5. What property allows the plasma membrane to regulate movement into and out of the cell?

A. Selective permeability at the cell periphery

B. Complete impermeability to dissolved substances

C. A rigid outer layer that prevents cellular exchange

D. An unrestricted barrier that permits every substance to pass

Answer: (A)

Explanation

The plasma membrane defines the cell periphery and is selectively permeable, allowing it to control entry and exit. An unrestricted barrier would not regulate movement across the cell boundary.

6. Which statement correctly describes the organization of proteins in the plasma membrane?

A. Both protein types remain within the cytoplasm without contacting the membrane

B. Integral proteins lie on the surface, while peripheral proteins span the bilayer

C. Integral proteins span the bilayer, while peripheral proteins lie on its surface

D. Both protein types span the bilayer and connect directly to its hydrophobic tails

Answer: (C)

Explanation

Integral proteins extend through the phospholipid bilayer, whereas peripheral proteins associate with its surface. This distinction reflects how each protein type interacts with the membrane.

7. Which description best defines the cytoplasm?

A. A selectively permeable boundary that encloses the cell and controls molecular entry

B. A genetic storage compartment that directs cellular activity from within the cell

C. A phospholipid structure with hydrophilic heads and hydrophobic tails

D. Material between the plasma membrane and nucleus that contains cytosol, organelles, and other cellular components

Answer: (D)

Explanation

The cytoplasm is the material between the plasma membrane and nucleus and includes cytosol, metabolites, enzymes, ions, organelles, and supramolecular structures. The other descriptions refer to the plasma membrane or nucleus rather than the cytoplasm.

8. Which process produces RNA rather than DNA within the nucleus?

A. Replication produces RNA from a DNA template

B. Chromosome separation produces RNA during cell division

C. Translation produces RNA from messenger RNA

D. Transcription produces RNA from a DNA template

Answer: (D)

Explanation

Transcription uses DNA as a template to produce RNA, whereas replication copies DNA to produce DNA. Translation instead uses messenger RNA to synthesize proteins.

9. Which pairing correctly matches each cytoskeletal component with its principal protein?

A. Microfilaments—heterogeneous proteins; microtubules—collagen; intermediate filaments—tubulin

B. Microfilaments—actin; microtubules—tubulin; intermediate filaments—heterogeneous proteins

C. Microfilaments—collagen; microtubules—heterogeneous proteins; intermediate filaments—actin

D. Microfilaments—tubulin; microtubules—actin; intermediate filaments—collagen

Answer: (B)

Explanation

Microfilaments are built from actin, microtubules from tubulin, and intermediate filaments from a varied group of proteins. The other pairings assign the major cytoskeletal proteins to the wrong structures.

10. A cell loses much of its cytoskeletal network. Which consequence is most likely?

A. Reduced mechanical support and impaired intracellular movement

B. Reduced ribosome production inside the nucleolus

C. Increased DNA storage and enhanced RNA transcription

D. Increased ATP production through mitochondrial enzymes

Answer: (A)

Explanation

The cytoskeleton maintains cell shape, resists mechanical stress, and supports movement within and by the cell. DNA storage, ribosome production, and ATP production are associated with other cellular structures.

11. What structural feature of mitochondria increases the membrane area available for ATP-producing reactions?

A. Smooth regions extending across the outer membrane

B. Ribosomes attached to the mitochondrial surface

C. Folds called cristae in the inner membrane

D. Enzymes distributed throughout the mitochondrial matrix

Answer: (C)

Explanation

The inner mitochondrial membrane folds into cristae, increasing the surface area for ATP-producing reactions. The outer membrane is smooth, while the matrix contains enzymes rather than membrane folds.

12. Which mitochondrial region contains enzymes for major catabolic pathways?

A. The intermembrane space

B. The outer mitochondrial membrane

C. The cristae themselves

D. The mitochondrial matrix

Answer: (D)

Explanation

The mitochondrial matrix contains enzymes that carry out major catabolic pathways. Cristae are folds of the inner membrane and should not be confused with the enzyme-rich matrix.

13. What is the primary energy-related product supplied by mitochondria to support cellular work?

A. Calcium ions, the cell’s principal energy currency

B. ATP, the cell’s major energy-carrying molecule

C. RNA, the cell’s primary hereditary molecule

D. Cholesterol, the main molecule driving cellular reactions

Answer: (B)

Explanation

Mitochondria produce ATP, which carries usable energy for cellular activities. RNA, calcium ions, and cholesterol have important cellular roles but are not the principal energy-carrying product of mitochondria.

14. Which structural distinction correctly compares rough and smooth endoplasmic reticulum?

A. Rough ER bears ribosomes, whereas smooth ER lacks them

B. Rough ER forms cristae, whereas smooth ER contains the matrix

C. Rough ER stores calcium, whereas smooth ER encloses the nucleus

D. Rough ER lacks ribosomes, whereas smooth ER bears them

Answer: (A)

Explanation

Rough ER is distinguished by ribosomes attached to its surface, while smooth ER lacks attached ribosomes. Cristae and the matrix are mitochondrial features, and the other functions do not define this ER distinction.

15. A cell specializes in producing steroid hormones and membrane lipids. Which organelle region would be especially important?

A. The rough endoplasmic reticulum

B. The Golgi apparatus

C. The nuclear envelope

D. The smooth endoplasmic reticulum

Answer: (D)

Explanation

Smooth ER synthesizes phospholipids, cholesterol, and steroid hormones, making it important in such a cell. Rough ER is more closely associated with protein synthesis, while the Golgi modifies and sorts proteins.

16. What is the principal role of the Golgi apparatus after proteins are synthesized in the endoplasmic reticulum?

A. It matures, modifies, packages, and sorts proteins into destination-bound vesicles

B. It synthesizes ribosomes and releases them into the cytoplasm

C. It copies DNA and transcribes RNA within the nuclear compartment

D. It folds the inner mitochondrial membrane into ATP-producing cristae

Answer: (A)

Explanation

The Golgi apparatus completes ER processing by modifying and maturing proteins, then packaging and sorting them into vesicles for delivery. DNA transcription, crista formation, and ribosome production belong to different cellular structures or processes.

17. Which feature best defines a lysosome?

A. A non-membrane-bound structure containing ribosomal RNA

B. A single-membrane vesicle containing acid hydrolases

C. A double-membrane organelle containing respiratory enzymes

D. A single-membrane vesicle containing oxidative enzymes

Answer: (B)

Explanation

Lysosomes are spherical vesicles bounded by one membrane and filled with acid hydrolases that digest cellular material. Peroxisomes also have a single membrane, but their characteristic enzymes are oxidative rather than digestive.

18. A cell needs to break down damaged organelles and recycle their molecular components. Which organelle performs this function?

A. The lysosome, using digestive enzymes to degrade cellular material

B. The peroxisome, using oxidative enzymes to neutralize harmful substances

C. The nucleolus, using ribosomal components to organize nuclear activity

D. The ribosome, using messenger RNA to assemble replacement proteins

Answer: (A)

Explanation

Lysosomes digest damaged cellular material and help recycle its components through acid hydrolase activity. Ribosomes synthesize proteins, so they do not carry out the degradation and recycling process described.

19. How do ribosomes produce cellular proteins?

A. They recycle damaged proteins using enzymes released into the cytoplasm

B. They translate messenger RNA using ribosomal RNA and proteins

C. They oxidize amino acids using catalase inside single-membrane vesicles

D. They digest messenger RNA using acid hydrolases and membrane vesicles

Answer: (B)

Explanation

Ribosomes are made of ribosomal RNA and proteins, and they translate messenger RNA to synthesize cellular proteins. Their lack of a surrounding membrane distinguishes them from lysosomes and peroxisomes.

20. A cell is exposed to hydrogen peroxide and very-long-chain fatty acids. Which organelle most directly helps process both substances?

A. The centrosome, using microtubules to organize cellular transport

B. The peroxisome, using oxidative enzymes such as catalase

C. The ribosome, using messenger RNA to synthesize protective proteins

D. The lysosome, using acid hydrolases for intracellular digestion

Answer: (B)

Explanation

Peroxisomes contain oxidative enzymes, including catalase, and participate in reactive oxygen species metabolism and β-oxidation of very-long-chain fatty acids. Lysosomes digest macromolecules, whereas ribosomes synthesize proteins and do not directly perform these oxidative reactions.