HESI A2 Biology Exam 2025
– Verified Questions and
Correct Answers with Expert
Rationales
Question 1
What is the primary source of energy for Earth's climate system?
a) Geothermal heat
b) Solar radiation
c) Nuclear fusion
d) Fossil fuels
Correct Answer: b) Solar radiation
Rationale: Solar radiation from the sun is the primary energy source driving Earth's climate
system, powering processes like photosynthesis, atmospheric circulation, and the water cycle.
Geothermal heat contributes minimally, nuclear fusion occurs in the sun, and fossil fuels are not
a natural climate driver.
Question 2
Which organelle is responsible for protein synthesis in eukaryotic cells?
a) Mitochondrion
b) Ribosome
c) Golgi apparatus
d) Lysosome
Correct Answer: b) Ribosome
Rationale: Ribosomes, found in the cytoplasm or attached to the endoplasmic reticulum,
synthesize proteins by translating mRNA into polypeptide chains. Mitochondria produce ATP,
the Golgi apparatus modifies proteins, and lysosomes degrade waste.
,Question 3
What is the primary function of the cell membrane?
a) Energy production
b) Regulating transport of substances
c) Protein synthesis
d) DNA replication
Correct Answer: b) Regulating transport of substances
Rationale: The cell membrane, a phospholipid bilayer, controls the movement of substances in
and out of the cell via selective permeability, maintaining homeostasis. Energy production occurs
in mitochondria, protein synthesis in ribosomes, and DNA replication in the nucleus.
Question 4
Which molecule carries genetic information in cells?
a) RNA
b) DNA
c) Protein
d) Lipid
Correct Answer: b) DNA
Rationale: DNA (deoxyribonucleic acid) contains the genetic blueprint for an organism, stored
in the nucleus. RNA translates this information, proteins perform functions, and lipids form
membranes and store energy.
Question 5
What process converts glucose into ATP in the presence of oxygen?
a) Glycolysis
b) Fermentation
c) Cellular respiration
d) Photosynthesis
Correct Answer: c) Cellular respiration
Rationale: Cellular respiration, including glycolysis, the Krebs cycle, and the electron transport
chain, converts glucose into ATP using oxygen. Glycolysis is only the first step, fermentation
occurs without oxygen, and photosynthesis produces glucose in plants.
, Question 6
Which type of bond holds water molecules together in liquid water?
a) Covalent bond
b) Ionic bond
c) Hydrogen bond
d) Peptide bond
Correct Answer: c) Hydrogen bond
Rationale: Hydrogen bonds form between the partially positive hydrogen of one water molecule
and the partially negative oxygen of another, giving water its unique properties. Covalent bonds
hold atoms within a molecule, ionic bonds involve ion attraction, and peptide bonds link amino
acids.
Question 7
What is the basic unit of life?
a) Atom
b) Molecule
c) Cell
d) Tissue
Correct Answer: c) Cell
Rationale: The cell is the smallest unit capable of performing life functions, such as metabolism
and reproduction. Atoms and molecules are smaller components, and tissues are groups of cells.
Question 8
Which phase of mitosis involves the separation of sister chromatids?
a) Prophase
b) Metaphase
c) Anaphase
d) Telophase
Correct Answer: c) Anaphase
Rationale: During anaphase, sister chromatids are pulled apart to opposite poles of the cell by
spindle fibers. Prophase condenses chromosomes, metaphase aligns them, and telophase reforms
nuclei.
– Verified Questions and
Correct Answers with Expert
Rationales
Question 1
What is the primary source of energy for Earth's climate system?
a) Geothermal heat
b) Solar radiation
c) Nuclear fusion
d) Fossil fuels
Correct Answer: b) Solar radiation
Rationale: Solar radiation from the sun is the primary energy source driving Earth's climate
system, powering processes like photosynthesis, atmospheric circulation, and the water cycle.
Geothermal heat contributes minimally, nuclear fusion occurs in the sun, and fossil fuels are not
a natural climate driver.
Question 2
Which organelle is responsible for protein synthesis in eukaryotic cells?
a) Mitochondrion
b) Ribosome
c) Golgi apparatus
d) Lysosome
Correct Answer: b) Ribosome
Rationale: Ribosomes, found in the cytoplasm or attached to the endoplasmic reticulum,
synthesize proteins by translating mRNA into polypeptide chains. Mitochondria produce ATP,
the Golgi apparatus modifies proteins, and lysosomes degrade waste.
,Question 3
What is the primary function of the cell membrane?
a) Energy production
b) Regulating transport of substances
c) Protein synthesis
d) DNA replication
Correct Answer: b) Regulating transport of substances
Rationale: The cell membrane, a phospholipid bilayer, controls the movement of substances in
and out of the cell via selective permeability, maintaining homeostasis. Energy production occurs
in mitochondria, protein synthesis in ribosomes, and DNA replication in the nucleus.
Question 4
Which molecule carries genetic information in cells?
a) RNA
b) DNA
c) Protein
d) Lipid
Correct Answer: b) DNA
Rationale: DNA (deoxyribonucleic acid) contains the genetic blueprint for an organism, stored
in the nucleus. RNA translates this information, proteins perform functions, and lipids form
membranes and store energy.
Question 5
What process converts glucose into ATP in the presence of oxygen?
a) Glycolysis
b) Fermentation
c) Cellular respiration
d) Photosynthesis
Correct Answer: c) Cellular respiration
Rationale: Cellular respiration, including glycolysis, the Krebs cycle, and the electron transport
chain, converts glucose into ATP using oxygen. Glycolysis is only the first step, fermentation
occurs without oxygen, and photosynthesis produces glucose in plants.
, Question 6
Which type of bond holds water molecules together in liquid water?
a) Covalent bond
b) Ionic bond
c) Hydrogen bond
d) Peptide bond
Correct Answer: c) Hydrogen bond
Rationale: Hydrogen bonds form between the partially positive hydrogen of one water molecule
and the partially negative oxygen of another, giving water its unique properties. Covalent bonds
hold atoms within a molecule, ionic bonds involve ion attraction, and peptide bonds link amino
acids.
Question 7
What is the basic unit of life?
a) Atom
b) Molecule
c) Cell
d) Tissue
Correct Answer: c) Cell
Rationale: The cell is the smallest unit capable of performing life functions, such as metabolism
and reproduction. Atoms and molecules are smaller components, and tissues are groups of cells.
Question 8
Which phase of mitosis involves the separation of sister chromatids?
a) Prophase
b) Metaphase
c) Anaphase
d) Telophase
Correct Answer: c) Anaphase
Rationale: During anaphase, sister chromatids are pulled apart to opposite poles of the cell by
spindle fibers. Prophase condenses chromosomes, metaphase aligns them, and telophase reforms
nuclei.
