[2026/2027 ATI TEAS PRACTICE TEST # 1EXAM: SCIENCE] –QUESTIONS AND CORRECT ANSWERS (VERIFIED ANSWERS) PLUS
RATIONALES 2026 Q&A | INSTANT DOWNLOAD PDF.
Core Domains
Human Anatomy and Physiology
Biology and Life Science Fundamentals
Chemical Principles and Reactions
Scientific Reasoning and Methodology
Cellular Biology and Genetics
Microbiology and Pathophysiology
Physical Science and Matter
Environmental and Earth Science Basics
Introduction
This assessment is meticulously designed to evaluate the foundational scientific knowledge required for entry into healthcare and nursing programs.
The purpose of this exam is to simulate the rigors of professional certification by assessing a candidate's grasp of the human body, chemical
interactions, and biological systems. The structure consists of multiple-choice questions and complex scenario-based inquiries that demand high-
level critical thinking. Candidates are expected to demonstrate skills in data interpretation, evidence-based reasoning, and the application of
theoretical concepts to real-world clinical and laboratory environments. Success in this exam reflects a deep-seated readiness for professional
decision-making and academic excellence.
1. Which of the following organelles is responsible for the synthesis of adenosine triphosphate (ATP) through cellular respiration?
A. Ribosome
B. Golgi apparatus
🟢 C. Mitochondria
D. Lysosome
🔴 RATIONALE: The mitochondria are known as the powerhouse of the cell because they perform aerobic respiration to generate ATP, which
provides energy for cellular processes.
, 2. In the human respiratory system, where does the actual exchange of gases occur?
A. Bronchioles
B. Trachea
C. Pharynx
🟢 D. Alveoli
🔴 RATIONALE: Alveoli are tiny air sacs at the end of the bronchial tree where oxygen enters the bloodstream and carbon dioxide is removed via
diffusion across the respiratory membrane.
3. Which of the following layers of the skin contains melanocytes, which produce the pigment responsible for skin color?
🟢 A. Epidermis
B. Dermis
C. Hypodermis
D. Stratum corneum
🔴 RATIONALE: Melanocytes are located in the basal layer of the epidermis. They produce melanin, which protects the skin from ultraviolet
radiation.
4. A scientist is testing the effect of fertilizer on plant growth. In this experiment, the height of the plant is considered which variable?
A. Independent variable
🟢 B. Dependent variable
C. Controlled variable
D. Hypothetical variable
🔴 RATIONALE: The dependent variable is the factor being measured or observed. In this case, the growth (height) depends on the amount of
fertilizer applied.
5. Which blood vessel carries deoxygenated blood from the heart to the lungs?
A. Aorta
B. Pulmonary vein
🟢 C. Pulmonary artery
D. Superior vena cava
🔴 RATIONALE: Unlike most arteries, the pulmonary artery carries deoxygenated blood away from the right ventricle of the heart to the lungs for
oxygenation.
, 6. Which of the following is a physical change rather than a chemical change?
🟢 A. Melting an ice cube
B. Burning a piece of wood
C. Rusting of an iron nail
D. Digestion of food by enzymes
🔴 RATIONALE: Melting is a phase change where the molecular structure of water remains the same (H2O), whereas the other options involve
chemical reactions that create new substances.
7. What is the primary function of the large intestine in the human digestive system?
A. Protein digestion
🟢 B. Water reabsorption
C. Nutrient absorption
D. Bile production
🔴 RATIONALE: While the small intestine absorbs most nutrients, the large intestine is primarily responsible for reabsorbing water and electrolytes
and forming solid waste.
8. A catalyst increases the rate of a chemical reaction by:
A. Increasing the temperature of the reactants
B. Increasing the concentration of the products
🟢 C. Lowering the activation energy
D. Changing the equilibrium constant
🔴 RATIONALE: Catalysts provide an alternative pathway for a reaction with a lower activation energy, allowing the reaction to proceed faster
without being consumed.
9. In genetics, an individual with two different alleles for a specific gene is described as:
A. Homozygous
🟢 B. Heterozygous
C. Recessive
D. Phenotypic
🔴 RATIONALE: Heterozygous refers to having one dominant and one recessive allele (e.g., Aa), whereas homozygous refers to having two of the
same alleles (e.g., AA or aa).
RATIONALES 2026 Q&A | INSTANT DOWNLOAD PDF.
Core Domains
Human Anatomy and Physiology
Biology and Life Science Fundamentals
Chemical Principles and Reactions
Scientific Reasoning and Methodology
Cellular Biology and Genetics
Microbiology and Pathophysiology
Physical Science and Matter
Environmental and Earth Science Basics
Introduction
This assessment is meticulously designed to evaluate the foundational scientific knowledge required for entry into healthcare and nursing programs.
The purpose of this exam is to simulate the rigors of professional certification by assessing a candidate's grasp of the human body, chemical
interactions, and biological systems. The structure consists of multiple-choice questions and complex scenario-based inquiries that demand high-
level critical thinking. Candidates are expected to demonstrate skills in data interpretation, evidence-based reasoning, and the application of
theoretical concepts to real-world clinical and laboratory environments. Success in this exam reflects a deep-seated readiness for professional
decision-making and academic excellence.
1. Which of the following organelles is responsible for the synthesis of adenosine triphosphate (ATP) through cellular respiration?
A. Ribosome
B. Golgi apparatus
🟢 C. Mitochondria
D. Lysosome
🔴 RATIONALE: The mitochondria are known as the powerhouse of the cell because they perform aerobic respiration to generate ATP, which
provides energy for cellular processes.
, 2. In the human respiratory system, where does the actual exchange of gases occur?
A. Bronchioles
B. Trachea
C. Pharynx
🟢 D. Alveoli
🔴 RATIONALE: Alveoli are tiny air sacs at the end of the bronchial tree where oxygen enters the bloodstream and carbon dioxide is removed via
diffusion across the respiratory membrane.
3. Which of the following layers of the skin contains melanocytes, which produce the pigment responsible for skin color?
🟢 A. Epidermis
B. Dermis
C. Hypodermis
D. Stratum corneum
🔴 RATIONALE: Melanocytes are located in the basal layer of the epidermis. They produce melanin, which protects the skin from ultraviolet
radiation.
4. A scientist is testing the effect of fertilizer on plant growth. In this experiment, the height of the plant is considered which variable?
A. Independent variable
🟢 B. Dependent variable
C. Controlled variable
D. Hypothetical variable
🔴 RATIONALE: The dependent variable is the factor being measured or observed. In this case, the growth (height) depends on the amount of
fertilizer applied.
5. Which blood vessel carries deoxygenated blood from the heart to the lungs?
A. Aorta
B. Pulmonary vein
🟢 C. Pulmonary artery
D. Superior vena cava
🔴 RATIONALE: Unlike most arteries, the pulmonary artery carries deoxygenated blood away from the right ventricle of the heart to the lungs for
oxygenation.
, 6. Which of the following is a physical change rather than a chemical change?
🟢 A. Melting an ice cube
B. Burning a piece of wood
C. Rusting of an iron nail
D. Digestion of food by enzymes
🔴 RATIONALE: Melting is a phase change where the molecular structure of water remains the same (H2O), whereas the other options involve
chemical reactions that create new substances.
7. What is the primary function of the large intestine in the human digestive system?
A. Protein digestion
🟢 B. Water reabsorption
C. Nutrient absorption
D. Bile production
🔴 RATIONALE: While the small intestine absorbs most nutrients, the large intestine is primarily responsible for reabsorbing water and electrolytes
and forming solid waste.
8. A catalyst increases the rate of a chemical reaction by:
A. Increasing the temperature of the reactants
B. Increasing the concentration of the products
🟢 C. Lowering the activation energy
D. Changing the equilibrium constant
🔴 RATIONALE: Catalysts provide an alternative pathway for a reaction with a lower activation energy, allowing the reaction to proceed faster
without being consumed.
9. In genetics, an individual with two different alleles for a specific gene is described as:
A. Homozygous
🟢 B. Heterozygous
C. Recessive
D. Phenotypic
🔴 RATIONALE: Heterozygous refers to having one dominant and one recessive allele (e.g., Aa), whereas homozygous refers to having two of the
same alleles (e.g., AA or aa).
