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HESI A2 Reading Comprehension & Biology/Chemistry Review Overview

The HESI A2 admission assessment evaluates critical reading literacy, life sciences (biology), and physical sciences (chemistry) across three distinct subtests (50 questions each). The Reading Comprehension subtest measures the ability to identify main ideas, supporting details, author tone, purpose, and logical inferences from short informational texts. The Biology subtest covers cellular structure and organelles, mitosis and meiosis, Mendelian genetics, DNA/RNA replication, and biological macromolecules. The Chemistry subtest evaluates atomic structure, isotopes, periodic trends, ionic and covalent bonding, chemical reactions, solutions, and pH scale calculations.

HESI Admissions Core · Reading & Science Modules

HESI A2 Reading Comprehension &
Biology/Chemistry Review

Master passage analysis, cell biology, genetics, atomic structure, and chemical bonding with our comprehensive HESI A2 preparation blueprint.

Reading Comprehension Cell Biology & Genetics Atomic Structure & Bonding Acids, Bases & Solutions
Subtest Specs Reading & Science
Reading: 50 Items

Time Limit: 50 Minutes

Chemistry: 25–30 Items

Time Limit: 25 Minutes

85%+ Target

Competitive Benchmark

Explore Reading Strategies →

Module Navigation Index

1. Reading Comprehension 2. Cell Biology & Organelles 3. Genetics & Macromolecules 4. Atomic Structure & Bonding 5. Solutions, Acids & Bases 6. Worked Practice Items 7. 4-Week Study Roadmap 8. Candidate FAQs
Subtest 1

1. HESI A2 Reading Comprehension Strategies

The HESI A2 Reading Comprehension subtest evaluates your ability to understand informational passages, extract explicit details, determine main ideas, evaluate author intent, and draw logical conclusions.

Core Question Categories

  • Main Idea / Theme: Identifying the primary message or central thesis of a passage.
  • Supporting Details: Locating specific facts, statistics, or evidence mentioned within the text.
  • Author's Purpose: Determining whether the author intends to inform, persuade, entertain, or instruct.
  • Logical Inferences: Drawing conclusions that are strongly implied by passage facts without introducing outside assumptions.

High-Yield Reading Tactics

  • Read Questions First: Scan the questions before reading the passage to identify specific keywords or targets.
  • Focus on Paragraph Openers: Topic sentences are usually located in the first or last sentence of each paragraph.
  • Eliminate Extreme Answers: Answer choices containing absolute words like always, never, all, or none are rarely correct in informational texts.
Subtest 2 · Life Sciences

2. Cell Biology & Organelle Functions

Cell biology questions on the HESI A2 test your knowledge of eukaryotic vs. prokaryotic cells and the specific roles of intracellular organelles:

Control & Powerhouse
  • Nucleus: Houses genetic material (DNA) and directs cellular replication.
  • Mitochondria: Site of cellular respiration and ATP energy production ("powerhouse of the cell").
  • Nucleolus: Produces ribosomal RNA (rRNA).
Protein Synthesis & Packaging
  • Ribosomes: Synthesizes proteins from amino acids using mRNA templates.
  • Rough ER: Studded with ribosomes; folds and transports proteins.
  • Golgi Apparatus: Modifies, packages, and ships proteins into vesicles.
Digestion & Transport
  • Lysosomes: Contain digestive enzymes to break down cellular debris and waste.
  • Smooth ER: Synthesizes lipids and detoxifies metabolic byproducts.
  • Cell Membrane: Provides selective permeability via a phospholipid bilayer.
Life Sciences

3. Genetics, Mitosis, Meiosis & Macromolecules

Cell Division: Mitosis vs. Meiosis

  • Mitosis: Produces 2 identical diploid ($2n$) somatic cells for growth, tissue repair, and asexual reproduction. (Stages: Prophase, Metaphase, Anaphase, Telophase).
  • Meiosis: Produces 4 genetically distinct haploid ($n$) gametes (sperm and egg cells) for sexual reproduction through two successive divisions.

Biological Macromolecules

  • Carbohydrates: Monomers are monosaccharides; primary source of short-term cellular energy (e.g., glucose, starch, glycogen).
  • Proteins: Monomers are amino acids linked by peptide bonds; function as enzymes, structural components, and antibodies.
  • Lipids: Hydrophobic molecules (fats, oils, phospholipids); provide long-term energy storage and cell membrane structure.
  • Nucleic Acids: Monomers are nucleotides (DNA and RNA); store and transmit genetic information.
Subtest 3 · Physical Sciences

4. Atomic Structure, Periodic Trends & Bonding

The HESI Chemistry subtest examines foundational chemical concepts, atomic models, and types of chemical bonds:

Subatomic Particles

  • Protons: Positively charged particles located in the nucleus. The atomic number equals the number of protons.
  • Neutrons: Neutral particles located in the nucleus. Isotopes are atoms of the same element with different numbers of neutrons.
  • Electrons: Negatively charged particles orbiting the nucleus in energy shells.

Chemical Bonding Types

  • Ionic Bonds: Formed through the complete transfer of electrons from a metal to a nonmetal, creating oppositely charged ions that attract (e.g., $NaCl$).
  • Covalent Bonds: Formed when two nonmetal atoms share pairs of valence electrons (e.g., $H_2O$, $CO_2$).
  • Hydrogen Bonds: Weak intermolecular attractions between a hydrogen atom bonded to an electronegative atom (N, O, F) and another electronegative atom.
Physical Sciences

5. Solutions, Concentrations & pH Scale

Solutions & Solutes

A solution is a homogeneous mixture consisting of a solute (the substance dissolved) dissolved in a solvent (the dissolving medium, usually water).

Acids & Hydrogen Ions

Acids release hydrogen ions ($H^+$) in water. They have a sour taste, turn litmus paper red, and measure below 7 on the pH scale.

Bases & Hydroxide Ions

Bases accept hydrogen ions or release hydroxide ions ($OH^-$). They taste bitter, feel slippery, and measure above 7 on the pH scale.

Exam Simulation

6. Worked HESI Practice Questions & Rationales

Category: Cell Biology HESI Practice Item 1

Question: Which cellular organelle is responsible for generating the majority of chemical energy (ATP) required for cellular metabolic activities?

A) Ribosome
B) Mitochondrion ✓
C) Golgi Apparatus
D) Lysosome
Biological Rationale:

Correct Answer: B. Mitochondria are known as the "powerhouse of the cell" because they generate adenosine triphosphate (ATP) via aerobic cellular respiration. Ribosomes synthesize proteins, the Golgi apparatus packages proteins, and lysosomes degrade waste.

Category: Chemistry / pH Scale HESI Practice Item 2

Question: A chemical solution has a measured pH of 3.2. How should this solution be classified?

A) Strong acid ✓
B) Neutral solution
C) Weak base
D) Strong base
Chemical Rationale:

Correct Answer: A. On the pH scale (ranging from 0 to 14), any value below 7.0 is acidic, with lower numbers representing higher acidity and higher hydrogen ion concentration. A pH of 3.2 indicates an acidic solution.

Preparation Roadmap

7. Recommended 4-Week Reading & Science Study Schedule

Week 1: Reading Comprehension Practice

Practice identifying main ideas, author purpose, and inference-based questions across timed 300-word informational passages.

Week 2: Cell Biology & Genetics

Review cell organelle functions, mitosis vs. meiosis stages, DNA/RNA replication, and macromolecule structures.

Week 3: Atomic Structure & Chemistry Basics

Study atomic numbers, isotopes, ionic/covalent bonds, solutions, and pH scale calculations.

Week 4: Timed Mock Exams & Review

Complete 3 full-length timed HESI A2 Reading, Biology, and Chemistry practice tests under exam conditions.

Frequently Asked Questions

8. Candidate Reading & Science FAQs

Are Biology and Chemistry tested together or separately on the HESI A2?

Depending on your nursing school's configuration, Biology and Chemistry may appear as standalone subtests (50 questions each) or combined into a general Science section. Check your school's specific testing requirements.

What is a competitive score for HESI Reading and Science?

Most nursing programs look for subtest scores of 80% or higher in Reading Comprehension, Biology, and Chemistry to ensure academic readiness.

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