NLN NEX Science Exam 2026/2027 – Complete Exam-Style
Questions with Detailed Rationales | 100% Verified – Pass
Guaranteed – A+ Graded
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INSTRUCTIONS: Select the best answer for each question. This examination assesses
foundational science knowledge for pre-nursing and allied health programs. Suggested
time: 60 minutes.
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Question 1
Which organelle is responsible for producing ATP through cellular respiration in
eukaryotic cells?
A. Nucleus
B. Ribosome
C. Mitochondrion
D. Golgi apparatus
Correct Answer: C
Rationale: Mitochondria are the site of aerobic cellular respiration, generating ATP via
the electron transport chain and oxidative phosphorylation. Distractor A is incorrect
because the nucleus houses genetic material and controls cell activities but does not
produce ATP. Distractor B is incorrect because ribosomes synthesize proteins.
Distractor D is incorrect because the Golgi apparatus modifies, sorts, and packages
proteins and lipids.
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Question 2
A patient with Type 1 diabetes has a fasting blood glucose of 280 mg/dL. Which
hormone is deficient, and which organ normally secretes it?
A. Glucagon, secreted by the pancreas
B. Insulin, secreted by the beta cells of the pancreatic islets
C. Cortisol, secreted by the adrenal cortex
D. Growth hormone, secreted by the anterior pituitary
Correct Answer: B
Rationale: Type 1 diabetes is characterized by autoimmune destruction of pancreatic
beta cells, resulting in insulin deficiency and inability to lower blood glucose. Distractor
A is incorrect because glucagon raises blood glucose. Distractor C is incorrect because
cortisol raises blood glucose but is not the primary deficiency in Type 1 diabetes.
Distractor D is incorrect because growth hormone affects metabolism but is not the
deficient hormone in diabetes.
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Question 3
During DNA replication, which enzyme synthesizes the new DNA strand by adding
complementary nucleotides?
A. DNA ligase
B. DNA polymerase
C. Helicase
D. RNA primase
Correct Answer: B
,Rationale: DNA polymerase synthesizes new DNA strands by adding
deoxyribonucleotides complementary to the template strand in the 5' to 3' direction.
Distractor A is incorrect because DNA ligase joins Okazaki fragments. Distractor C is
incorrect because helicase unwinds the double helix. Distractor D is incorrect because
RNA primase synthesizes RNA primers to initiate replication.
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Question 4
A 68-year-old patient presents with a fracture of the femoral neck. Which type of bone
cell is primarily responsible for breaking down and removing damaged bone tissue
during the healing process?
A. Osteoblast
B. Osteoclast
C. Chondrocyte
D. Fibroblast
Correct Answer: B
Rationale: Osteoclasts are multinucleated cells that secrete acids and enzymes to
resorb bone matrix, clearing damaged tissue to allow new bone formation. Distractor A
is incorrect because osteoblasts build new bone. Distractor C is incorrect because
chondrocytes produce cartilage. Distractor D is incorrect because fibroblasts produce
collagen in connective tissue but do not resorb bone.
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Question 5
Which chamber of the heart receives oxygenated blood from the pulmonary circulation?
A. Right atrium
, B. Right ventricle
C. Left atrium
D. Left ventricle
Correct Answer: C
Rationale: The left atrium receives oxygenated blood returning from the lungs via the
pulmonary veins. Distractor A is incorrect because the right atrium receives
deoxygenated blood from the systemic circulation. Distractor B is incorrect because the
right ventricle pumps deoxygenated blood to the lungs. Distractor D is incorrect
because the left ventricle receives blood from the left atrium and pumps it to the body.
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Question 6
In a chemical reaction, which subatomic particle is primarily responsible for forming
covalent bonds between atoms?
A. Protons
B. Neutrons
C. Electrons
D. Photons
Correct Answer: C
Rationale: Covalent bonds form when atoms share pairs of valence electrons to achieve
stable electron configurations. Distractor A is incorrect because protons are positively
charged and reside in the nucleus. Distractor B is incorrect because neutrons are neutral
and in the nucleus. Distractor D is incorrect because photons are particles of light
energy, not involved in chemical bonding.
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────────────────────────
Questions with Detailed Rationales | 100% Verified – Pass
Guaranteed – A+ Graded
═══════════════════════════════════════════════════════
════════════════════════
INSTRUCTIONS: Select the best answer for each question. This examination assesses
foundational science knowledge for pre-nursing and allied health programs. Suggested
time: 60 minutes.
═══════════════════════════════════════════════════════
════════════════════════
Question 1
Which organelle is responsible for producing ATP through cellular respiration in
eukaryotic cells?
A. Nucleus
B. Ribosome
C. Mitochondrion
D. Golgi apparatus
Correct Answer: C
Rationale: Mitochondria are the site of aerobic cellular respiration, generating ATP via
the electron transport chain and oxidative phosphorylation. Distractor A is incorrect
because the nucleus houses genetic material and controls cell activities but does not
produce ATP. Distractor B is incorrect because ribosomes synthesize proteins.
Distractor D is incorrect because the Golgi apparatus modifies, sorts, and packages
proteins and lipids.
,───────────────────────────────────────────────────────
────────────────────────
Question 2
A patient with Type 1 diabetes has a fasting blood glucose of 280 mg/dL. Which
hormone is deficient, and which organ normally secretes it?
A. Glucagon, secreted by the pancreas
B. Insulin, secreted by the beta cells of the pancreatic islets
C. Cortisol, secreted by the adrenal cortex
D. Growth hormone, secreted by the anterior pituitary
Correct Answer: B
Rationale: Type 1 diabetes is characterized by autoimmune destruction of pancreatic
beta cells, resulting in insulin deficiency and inability to lower blood glucose. Distractor
A is incorrect because glucagon raises blood glucose. Distractor C is incorrect because
cortisol raises blood glucose but is not the primary deficiency in Type 1 diabetes.
Distractor D is incorrect because growth hormone affects metabolism but is not the
deficient hormone in diabetes.
───────────────────────────────────────────────────────
────────────────────────
Question 3
During DNA replication, which enzyme synthesizes the new DNA strand by adding
complementary nucleotides?
A. DNA ligase
B. DNA polymerase
C. Helicase
D. RNA primase
Correct Answer: B
,Rationale: DNA polymerase synthesizes new DNA strands by adding
deoxyribonucleotides complementary to the template strand in the 5' to 3' direction.
Distractor A is incorrect because DNA ligase joins Okazaki fragments. Distractor C is
incorrect because helicase unwinds the double helix. Distractor D is incorrect because
RNA primase synthesizes RNA primers to initiate replication.
───────────────────────────────────────────────────────
────────────────────────
Question 4
A 68-year-old patient presents with a fracture of the femoral neck. Which type of bone
cell is primarily responsible for breaking down and removing damaged bone tissue
during the healing process?
A. Osteoblast
B. Osteoclast
C. Chondrocyte
D. Fibroblast
Correct Answer: B
Rationale: Osteoclasts are multinucleated cells that secrete acids and enzymes to
resorb bone matrix, clearing damaged tissue to allow new bone formation. Distractor A
is incorrect because osteoblasts build new bone. Distractor C is incorrect because
chondrocytes produce cartilage. Distractor D is incorrect because fibroblasts produce
collagen in connective tissue but do not resorb bone.
───────────────────────────────────────────────────────
────────────────────────
Question 5
Which chamber of the heart receives oxygenated blood from the pulmonary circulation?
A. Right atrium
, B. Right ventricle
C. Left atrium
D. Left ventricle
Correct Answer: C
Rationale: The left atrium receives oxygenated blood returning from the lungs via the
pulmonary veins. Distractor A is incorrect because the right atrium receives
deoxygenated blood from the systemic circulation. Distractor B is incorrect because the
right ventricle pumps deoxygenated blood to the lungs. Distractor D is incorrect
because the left ventricle receives blood from the left atrium and pumps it to the body.
───────────────────────────────────────────────────────
────────────────────────
Question 6
In a chemical reaction, which subatomic particle is primarily responsible for forming
covalent bonds between atoms?
A. Protons
B. Neutrons
C. Electrons
D. Photons
Correct Answer: C
Rationale: Covalent bonds form when atoms share pairs of valence electrons to achieve
stable electron configurations. Distractor A is incorrect because protons are positively
charged and reside in the nucleus. Distractor B is incorrect because neutrons are neutral
and in the nucleus. Distractor D is incorrect because photons are particles of light
energy, not involved in chemical bonding.
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