Below is a sample revision test designed to help you review key concepts that are covered in Biology
in Focus, 2nd AP® Edition (Urry, 2017). Chapter 1-25 Each question is followed by a rationale
explaining the answer. You can use these questions to check your understanding and identify areas
for further review.
Revision Test: Sample Questions with Rationale
Question 1: Cell Structure & Function
Which organelle is primarily responsible for generating the cell’s ATP?
A. Nucleus
B. Mitochondrion
C. Endoplasmic reticulum
D. Golgi apparatus
Correct Answer: B. Mitochondrion
Rationale:
Mitochondria are known as the “powerhouses” of the cell because they generate ATP through cellular
respiration. The nucleus stores genetic information, the ER is involved in protein and lipid synthesis, and
the Golgi apparatus modifies and packages proteins.
Question 2: Membrane Dynamics
Which of the following best describes the fluid mosaic model of the plasma membrane?
A. A static layer of phospholipids with proteins fixed in place
B. A bilayer in which proteins float freely and lipids are rigidly structured
C. A dynamic, flexible layer with proteins embedded in or attached to a phospholipid bilayer
D. A collection of randomly arranged proteins with a constant lipid composition
Correct Answer: C. A dynamic, flexible layer with proteins embedded in or attached to a phospholipid
bilayer
Rationale:
The fluid mosaic model describes the plasma membrane as a fluid structure where lipids and proteins
can move laterally. This flexibility is essential for processes like cell signaling and substance transport.
Question 3: Genetics – DNA Replication
Which enzyme is responsible for synthesizing a new strand of DNA during replication?
A. DNA ligase
B. RNA polymerase
C. DNA polymerase
D. Helicase
,Correct Answer: C. DNA polymerase
Rationale:
DNA polymerase is the enzyme that adds nucleotides to the growing DNA strand during replication.
Helicase unwinds the DNA double helix, RNA polymerase synthesizes RNA during transcription, and DNA
ligase joins Okazaki fragments on the lagging strand.
Question 4: Protein Synthesis
During translation, which cellular structure is the site where protein synthesis occurs?
A. Nucleus
B. Mitochondrion
C. Ribosome
D. Endoplasmic reticulum
Correct Answer: C. Ribosome
Rationale:
Ribosomes are the molecular machines that read messenger RNA (mRNA) and synthesize proteins by
linking amino acids in the order specified by the mRNA sequence. Ribosomes can be free in the cytosol
or bound to the rough endoplasmic reticulum.
Question 5: Evolution
Natural selection results in which of the following outcomes?
A. Random mutation of traits in a population
B. The accumulation of beneficial traits over generations
C. Immediate change in an organism’s genetic makeup
D. The elimination of all genetic variation
Correct Answer: B. The accumulation of beneficial traits over generations
Rationale:
Natural selection is the process where organisms with traits that are better suited to their environment
tend to survive and reproduce. This leads to the accumulation of advantageous traits over time. It is not
a random process and does not eliminate all variation, as some diversity is necessary for adaptation.
Question 6: Ecology – Ecosystem Dynamics
Which of the following best defines an ecosystem?
A. A group of individuals of the same species living in a specific area
B. A community of organisms interacting with one another and with their physical environment
C. The complete set of genes within an organism
D. A collection of nonliving components only
Correct Answer: B. A community of organisms interacting with one another and with their physical
environment
, Rationale:
An ecosystem includes both biotic (living) components and abiotic (nonliving) factors such as soil, water,
and climate. It is the interaction between these components that defines ecosystem dynamics.
Question 7: Photosynthesis
In the light-dependent reactions of photosynthesis, what is the primary role of chlorophyll?
A. To produce ATP directly from ADP
B. To capture light energy and convert it into chemical energy
C. To fix carbon dioxide into sugars
D. To break down water into oxygen and protons
Correct Answer: B. To capture light energy and convert it into chemical energy
Rationale:
Chlorophyll is the pigment that absorbs light, which is then used to drive the conversion of ADP and
NADP⁺ into the energy carriers ATP and NADPH during the light-dependent reactions. Water splitting
(photolysis) occurs in this process too, but the pigment’s main role is light capture.
Question 8: Cellular Respiration
Which process produces the majority of ATP in cellular respiration?
A. Glycolysis
B. Citric acid cycle
C. Oxidative phosphorylation
D. Fermentation
Correct Answer: C. Oxidative phosphorylation
Rationale:
Oxidative phosphorylation, which occurs in the mitochondria, is responsible for producing the majority
of ATP via the electron transport chain and chemiosmosis. Glycolysis and the citric acid cycle produce
ATP, but in much smaller amounts, while fermentation is an anaerobic process that produces minimal
ATP.
Question 9: Homeostasis
Homeostasis in the human body is maintained primarily by which of the following systems?
A. The integumentary system
B. The nervous and endocrine systems
C. The skeletal system
D. The respiratory system
Correct Answer: B. The nervous and endocrine systems
Rationale:
Homeostasis—the process of maintaining a stable internal environment—is controlled by the nervous
in Focus, 2nd AP® Edition (Urry, 2017). Chapter 1-25 Each question is followed by a rationale
explaining the answer. You can use these questions to check your understanding and identify areas
for further review.
Revision Test: Sample Questions with Rationale
Question 1: Cell Structure & Function
Which organelle is primarily responsible for generating the cell’s ATP?
A. Nucleus
B. Mitochondrion
C. Endoplasmic reticulum
D. Golgi apparatus
Correct Answer: B. Mitochondrion
Rationale:
Mitochondria are known as the “powerhouses” of the cell because they generate ATP through cellular
respiration. The nucleus stores genetic information, the ER is involved in protein and lipid synthesis, and
the Golgi apparatus modifies and packages proteins.
Question 2: Membrane Dynamics
Which of the following best describes the fluid mosaic model of the plasma membrane?
A. A static layer of phospholipids with proteins fixed in place
B. A bilayer in which proteins float freely and lipids are rigidly structured
C. A dynamic, flexible layer with proteins embedded in or attached to a phospholipid bilayer
D. A collection of randomly arranged proteins with a constant lipid composition
Correct Answer: C. A dynamic, flexible layer with proteins embedded in or attached to a phospholipid
bilayer
Rationale:
The fluid mosaic model describes the plasma membrane as a fluid structure where lipids and proteins
can move laterally. This flexibility is essential for processes like cell signaling and substance transport.
Question 3: Genetics – DNA Replication
Which enzyme is responsible for synthesizing a new strand of DNA during replication?
A. DNA ligase
B. RNA polymerase
C. DNA polymerase
D. Helicase
,Correct Answer: C. DNA polymerase
Rationale:
DNA polymerase is the enzyme that adds nucleotides to the growing DNA strand during replication.
Helicase unwinds the DNA double helix, RNA polymerase synthesizes RNA during transcription, and DNA
ligase joins Okazaki fragments on the lagging strand.
Question 4: Protein Synthesis
During translation, which cellular structure is the site where protein synthesis occurs?
A. Nucleus
B. Mitochondrion
C. Ribosome
D. Endoplasmic reticulum
Correct Answer: C. Ribosome
Rationale:
Ribosomes are the molecular machines that read messenger RNA (mRNA) and synthesize proteins by
linking amino acids in the order specified by the mRNA sequence. Ribosomes can be free in the cytosol
or bound to the rough endoplasmic reticulum.
Question 5: Evolution
Natural selection results in which of the following outcomes?
A. Random mutation of traits in a population
B. The accumulation of beneficial traits over generations
C. Immediate change in an organism’s genetic makeup
D. The elimination of all genetic variation
Correct Answer: B. The accumulation of beneficial traits over generations
Rationale:
Natural selection is the process where organisms with traits that are better suited to their environment
tend to survive and reproduce. This leads to the accumulation of advantageous traits over time. It is not
a random process and does not eliminate all variation, as some diversity is necessary for adaptation.
Question 6: Ecology – Ecosystem Dynamics
Which of the following best defines an ecosystem?
A. A group of individuals of the same species living in a specific area
B. A community of organisms interacting with one another and with their physical environment
C. The complete set of genes within an organism
D. A collection of nonliving components only
Correct Answer: B. A community of organisms interacting with one another and with their physical
environment
, Rationale:
An ecosystem includes both biotic (living) components and abiotic (nonliving) factors such as soil, water,
and climate. It is the interaction between these components that defines ecosystem dynamics.
Question 7: Photosynthesis
In the light-dependent reactions of photosynthesis, what is the primary role of chlorophyll?
A. To produce ATP directly from ADP
B. To capture light energy and convert it into chemical energy
C. To fix carbon dioxide into sugars
D. To break down water into oxygen and protons
Correct Answer: B. To capture light energy and convert it into chemical energy
Rationale:
Chlorophyll is the pigment that absorbs light, which is then used to drive the conversion of ADP and
NADP⁺ into the energy carriers ATP and NADPH during the light-dependent reactions. Water splitting
(photolysis) occurs in this process too, but the pigment’s main role is light capture.
Question 8: Cellular Respiration
Which process produces the majority of ATP in cellular respiration?
A. Glycolysis
B. Citric acid cycle
C. Oxidative phosphorylation
D. Fermentation
Correct Answer: C. Oxidative phosphorylation
Rationale:
Oxidative phosphorylation, which occurs in the mitochondria, is responsible for producing the majority
of ATP via the electron transport chain and chemiosmosis. Glycolysis and the citric acid cycle produce
ATP, but in much smaller amounts, while fermentation is an anaerobic process that produces minimal
ATP.
Question 9: Homeostasis
Homeostasis in the human body is maintained primarily by which of the following systems?
A. The integumentary system
B. The nervous and endocrine systems
C. The skeletal system
D. The respiratory system
Correct Answer: B. The nervous and endocrine systems
Rationale:
Homeostasis—the process of maintaining a stable internal environment—is controlled by the nervous
