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Overview
This study guide covers the essential chemistry and biology concepts tested on the TEAS exam, spanning atomic structure, chemical bonding, biological macromolecules, cell biology, genetics, and human body systems. Mastery of these topics requires understanding both foundational definitions and how concepts interconnect across disciplines. Use this guide alongside active recall practice to maximize retention and exam performance.
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Section 1: Atomic Structure & The Periodic Table
Core Concepts
The atom is the fundamental unit of matter, composed of protons, neutrons, and electrons. Understanding atomic structure is the foundation for all chemistry on the TEAS.
• Atomic number = number of protons → uniquely identifies every element
• Atomic mass = protons + neutrons (electrons have negligible mass)
• Neutrons can vary within the same element, creating isotopes
Periodic Table Trends
| Direction | Electronegativity | Atomic Radius |
|-----------|------------------|---------------|
| Left → Right (period) | Increases | Decreases |
| Top → Bottom (group) | Decreases | Increases |
• Electronegativity increases left to right because nuclear charge increases while shielding stays roughly constant, pulling electrons more strongly
• Elements in the same group (column) share the same number of valence electrons → similar chemical behavior
Key Terms
• Atomic number – number of protons in the nucleus
• Atomic mass – total protons + neutrons in the nucleus
• Isotopes – same element (same protons), different number of neutrons, different atomic masses
• Electronegativity – an atom's ability to attract electrons in a chemical bond
• Valence electrons – outermost electrons that determine chemical reactivity
• Period – horizontal row on the periodic table
• Group – vertical column on the periodic table
Watch Out For ⚠️
• Do not confuse atomic number with atomic mass. Atomic number = protons only; atomic mass includes neutrons.
• Isotopes are still the same element — same protons, different neutrons. They do NOT become a new element.
• Electronegativity trends go left to right across a period and bottom to top up a group. Noble gases are typically excluded from electronegativity discussions.
• Elements in the same group share properties; elements in the same period do NOT share the same number of valence electrons.
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Section 2: Chemical Bonds & Reactions
Types of Chemical Bonds
| Bond Type | Mechanism | Strength | Example |
|-----------|-----------|----------|---------|
| Ionic | Electron transfer | Strong (in solid) | NaCl |
| Covalent | Electron sharing | Moderate–Strong | H₂O |
| Hydrogen | Weak electrostatic attraction | Weak | Water, DNA |
• Ionic bonds: one atom loses an electron (becomes a cation, positively charged), another gains it (becomes an anion, negatively charged)
• Hydrogen bonds: H bonded to an electronegative atom (N, O, F) is attracted to another electronegative atom — critical for water's unique properties and DNA's double helix stability
Chemical Reactions: Key Principles
• Law of Conservation of Mass: mass of reactants = mass of products; atoms are rearranged, never created or destroyed → equations must be balanced
• Exothermic reaction: releases energy (heat) to surroundings; products have less energy than reactants (e.g., combustion)
• Endothermic reaction: absorbs energy from surroundings; products have more energy than reactants
• Activation energy: the minimum energy needed to start a reaction
• Temperature & reaction rate: higher temperature → faster molecular movement → more frequent and energetic collisions → faster reaction rate
The pH Scale
```
0 ——————————— 7 ——————————— 14
ACIDIC NEUTRAL BASIC/ALKALINE
```
• pH = 7: neutral (pure water)
• pH < 7: acidic (more H⁺ ions)
• pH > 7: basic/alkaline (more OH⁻ ions)
• Each unit represents a 10-fold change in H⁺ concentration (logarithmic scale)
Key Terms
• Ionic bond – bond formed by electron transfer between atoms
• Covalent bond – bond formed by electron sharing
• Hydrogen bond – weak attraction between H and an electronegative atom
• Cation – positively charged ion (lost electrons)
• Anion – negatively charged ion (gained electrons)
• Exothermic – reaction that releases energy
• Endothermic – reaction that absorbs energy
• Activation energy – minimum energy required to initiate a reaction
• pH – measure of acidity/alkalinity (0–14 scale)
Watch Out For ⚠️
• Hydrogen bonds are not the same as a covalent bond involving hydrogen. They are intermolecular (between molecules), not intramolecular (within a molecule).
• An exothermic reaction releases heat — the surroundings get warmer. Don't confuse "releasing energy" with the reaction "gaining" something.
• The pH scale is logarithmic: pH 5 is 10× more acidic than pH 6, not just slightly more acidic.
• Higher temperature speeds up reactions by providing energy to overcome activation energy — this concept connects to enzyme biology in the next section.
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Section 3: Biological Macromolecules
The Four Macromolecules at a Glance
| Macromolecule | Monomer | Bond | Key Functions |
|---------------|---------|------|---------------|
| Carbohydrates | Monosaccharides | Glycosidic | Quick energy, structural (cellulose) |
| Lipids | Fatty acids + glycerol | Ester | Long-term energy storage, cell membranes, hormones |
| Proteins | Amino acids | Peptide | Structure, enzymes, transport, signaling |
| Nucleic Acids | Nucleotides | Phosphodiester | Genetic info (DNA), protein synthesis (RNA) |
Proteins in Detail
• Built from amino acids linked by peptide bonds (via dehydration synthesis — water is removed)
• Enzymes are proteins that act as biological catalysts:
- Lower activation energy
- Speed up reactions
- Are NOT consumed or permanently changed
- Are highly specific (lock-and-key or induced fit model)
DNA vs. RNA
| Feature | DNA | RNA |
|---------|-----|-----|
| Sugar | Deoxyribose | Ribose |
| Bases | A, T, G, C | A, U, G, C |
| Strands | Double-stranded | Single-stranded |
| Function | Stores genetic info | Protein synthesis |
| Location | Nucleus (mainly) | Nucleus & cytoplasm |
> Memory tip: DNA has Thymine; RNA has Uracil. Think: DNA = The original; RNA = Use uracil.
Lipids
• Phospholipids: form the bilayer of cell membranes (hydrophilic heads face outward, hydrophobic tails face inward)
• Triglycerides: long-term energy storage
• Steroids (including cholesterol): serve as hormones and membrane components
• Lipids are not built from a repeating monomer chain like other macromolecules
Key Terms
• Macromolecule – large biological polymer
• Monomer – small repeating subunit
• Polymer – long chain of monomers
• Dehydration synthesis – building polymers by removing water
• Hydrolysis – breaking polymers by adding water
• Peptide bond – bond linking amino acids in a protein
• Enzyme – protein catalyst
• Nucleotide – monomer of nucleic acids (phosphate + sugar + nitrogenous base)
Watch Out For ⚠️
• Lipids are not true polymers like the other three macromolecules — they don't have a single repeating monomer unit.
• Enzymes lower activation energy but do not change the overall energy released or absorbed in a reaction.
• DNA uses thymine (T); RNA uses uracil (U). This is a classic TEAS question.
• Dehydration synthesis builds molecules (releases water); hydrolysis breaks them down (uses water). Know both directions.
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Section 4: Cell Biology
Prokaryotes vs. Eukaryotes
| Feature | Prokaryotic | Eukaryotic |
|---------|-------------|------------|
| Nucleus | ❌ No membrane-bound nucleus | ✅ True nucleus with membrane |
| Organelles | ❌ No membrane-bound organelles | ✅ Membrane-bound organelles |
| Ribosomes | ✅ Present (smaller, 70S) | ✅ Present (larger, 80S) |
| Examples | Bacteria, Archaea | Plants, animals, fungi, protists |
Key Organelles & Functions
| Organelle | Function |
|-----------|----------|
| Mitochondria | ATP production via cellular respiration ("powerhouse") |
| Ribosomes | Protein synthesis (translation) |
| Nucleus | Stores DNA; controls cell activities |
| Endoplasmic Reticulum (ER) | Protein (rough ER) and lipid (smooth ER) processing |
| Golgi Apparatus | Packages and ships proteins |
| Lysosomes | Cellular digestion (break down waste) |
| Cell Membrane | Controls what enters/exits the cell |
Cellular Transport
• Passive transport (no energy required):
- Diffusion: movement from high → low concentration
- Osmosis: water movement across a semipermeable membrane from low solute → high solute concentration
- Facilitated diffusion: uses protein channels, still high → low concentration
• Active transport (energy/ATP required): moves substances against concentration gradient (low → high)
• Endocytosis: cell engulfs large particles by wrapping membrane around them → forms a vesicle
• Exocytosis: cell expels materials by fusing vesicles with the membrane
Cellular Respiration (Summary)
```
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP
(Glucose + Oxygen → Carbon Dioxide + Water + Energy)
```
• Occurs in the mitochondria
• Produces ATP — the cell's energy currency
• Three stages: Glycolysis (cytoplasm) → Krebs Cycle → Oxidative Phosphorylation (electron transport chain)
Key Terms
• Prokaryote – cell without a membrane-bound nucleus
• Eukaryote – cell with a true, membrane-bound nucleus
• Mitochondria – organelle that produces ATP
• Ribosome – site of protein synthesis
• Osmosis – passive water movement across a semipermeable membrane
• Endocytosis – process of engulfing particles into the cell
• ATP – adenosine triphosphate; primary energy currency of cells
• Semipermeable membrane – membrane that allows only certain substances to pass
Watch Out For ⚠️
• Osmosis is about water movement specifically. Water always moves toward higher solute concentration (lower water concentration).
• Both prokaryotes and eukaryotes have ribosomes — ribosomes are not exclusively eukaryotic.
• Cellular respiration occurs in mitochondria, not chloroplasts (that's photosynthesis).
• Endocytosis brings things into the cell; exocytosis sends things out. "Endo" = inside, "Exo" = outside.
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Section 5: Genetics & Heredity
The Central Dogma
```
DNA → (Transcription) → mRNA → (Translation) → Protein
```
• Transcription: DNA is used as a template to make mRNA; occurs in the nucleus
• Translation: mRNA is read by ribosomes to assemble amino acids into a protein; occurs in the cytoplasm
Mendelian Genetics
• Dominant allele: expressed whenever at least one copy is present; written as uppercase (A)
• Recessive allele: expressed only when two copies are present (homozygous recessive); written as lowercase (a)
| Genotype | Description | Phenotype |
|----------|-------------|-----------|
| AA | Homozygous dominant | Dominant trait |
| Aa | Heterozygous | Dominant trait |
| aa | Homozygous recessive | Recessive trait |
• Genotype: the actual allele combination (genetic blueprint)
• Phenotype: the observable trait expressed (what you see)
Cell Division: Mitosis vs. Meiosis
| Feature | Mitosis | Meiosis |
|---------|---------|---------|
| Purpose | Growth, repair, asexual reproduction | Gamete production (sex cells) |
| Daughter cells produced | 2 | 4 |
| Chromosome number | Same as parent (diploid, 2n) | Half of parent (haploid, n) |
| Genetic outcome | Genetically identical | Genetically unique |
| Location | All body (somatic) cells | Reproductive organs |
Mutations
• A mutation is a permanent change in the DNA nucleotide sequence
• Causes: replication errors, radiation, chemical mutagens
• May be beneficial, neutral, or harmful
• Not all mutations affect the protein produced (silent mutations due to codon redundancy)
Key Terms
• Central dogma – DNA → RNA → Protein
• Transcription – making mRNA from a DNA template
• Translation – making a protein from an mRNA sequence
• Allele – a version of a gene
• Dominant – allele expressed with one or two copies present
• Recessive – allele expressed only with two copies present
• Genotype – genetic makeup (allele combination)
• Phenotype – observable physical trait
• Mitosis – cell division producing 2 identical diploid cells
• Meiosis – cell division producing 4 unique haploid gametes
• Diploid (2n) – full set of chromosomes (46 in humans)
• Haploid (n) – half set of chromosomes (23 in humans)
• Mutation – permanent change in DNA sequence
Watch Out For ⚠️
• Mitosis ≠ Meiosis: Mitosis = 2 identical cells (body cells); Meiosis = 4 unique cells (sex cells).
• A heterozygous (Aa) individual will show the dominant phenotype, not a blend.
• Transcription happens in the nucleus; translation happens at ribosomes in the cytoplasm.
• Mutations are permanent, but they are not always harmful. Many are silent or neutral.
• DNA uses thymine; mRNA uses uracil (reinforcement from the macromolecules section).
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Section 6: Human Body Systems & Homeostasis
Homeostasis
Homeostasis is the maintenance of a stable internal environment despite external changes.
• Regulated variables: body temperature (~37°C), blood pH (~7.4), blood glucose, water balance
• Mechanism: negative feedback loops — a change triggers a response that counteracts the change and restores balance
• Example: blood glucose rises → insulin released → glucose taken up by cells → blood glucose returns to normal
Blood & The Cardiovascular System
• Red blood cells (erythrocytes):
- Transport O₂ from lungs to tissues
- Carry CO₂ back to lungs
- Use hemoglobin (iron-containing protein) to bind gases
- Lack a nucleus at maturity (can't divide)
The Kidneys & Nephron
• Nephron = functional unit of the kidney
• Three processes:
1. Filtration: blood filtered under pressure (removes waste + useful substances)
2. Reabsorption: useful substances (glucose, water, ions) returned to blood
3.