TEAS 7 Biology: Cells, Genetics, and Macromolecules

What TEAS Biology Actually Tests

ATI lists biology as one of three Science content areas alongside human anatomy and physiology and chemistry. In practice, biology questions appear in 6-10 items on the Science section, distributed across four topic areas:

1. Cell structure and function
2. Cell division (mitosis and meiosis)
3. Genetics (Mendelian inheritance, DNA, protein synthesis)
4. Biological macromolecules

None of these is independently large. You can study them in any order, though the sequence above builds knowledge naturally — cells contain organelles, organelles divide, division is regulated by genes, genes code for macromolecules.

Topic 1: Cell Structure and Function

Master the major organelles and their functions. The TEAS will not ask for a list of every organelle — but it will ask which organelle does what, or what type of cell has which feature.

• Nucleus: Contains DNA. Controls cell activities. Surrounded by nuclear membrane with pores.
• Mitochondria: Power plant. Site of cellular respiration. Produces ATP. Has its own DNA (an exam favorite).
• Ribosomes: Site of protein synthesis. Found free in cytoplasm or attached to rough ER.
• Endoplasmic reticulum (ER): Rough ER (with ribosomes) makes proteins. Smooth ER (no ribosomes) makes lipids and detoxifies.
• Golgi apparatus: Modifies, sorts, and ships proteins from the ER.
• Lysosomes: Digestion. Breaks down waste, old organelles, and ingested material.
• Cell membrane: Phospholipid bilayer. Selectively permeable. Contains embedded proteins.
• Cell wall (plants only): Rigid outer layer made of cellulose. Provides structure.
• Chloroplasts (plants only): Site of photosynthesis. Contain chlorophyll.
• Vacuoles: Storage. Large central vacuole in plant cells.
• Cytoskeleton: Internal scaffold. Microtubules, microfilaments, intermediate filaments.

Membrane Transport

• Passive transport: No energy required. Includes diffusion (high to low concentration), osmosis (water across a membrane), and facilitated diffusion (through protein channels).
• Active transport: Requires ATP. Moves substances against a concentration gradient. Sodium-potassium pump is the classic example.
• Endocytosis and exocytosis: Bulk transport of large molecules. Vesicles bring substances in or out.
• Tonicity: Hypotonic (cells gain water and swell), isotonic (no net water movement), hypertonic (cells lose water and shrink).

Prokaryotic vs. Eukaryotic Cells

• Prokaryotes (bacteria, archaea): No nucleus, no membrane-bound organelles, smaller, circular DNA.
• Eukaryotes (animals, plants, fungi, protists): Membrane-bound nucleus, membrane-bound organelles, larger, linear DNA in chromosomes.

Topic 2: Cell Division

Mitosis

Cell division for somatic (body) cells. Produces two genetically identical diploid daughter cells. The phases follow the acronym PMAT:

• Prophase: Chromosomes condense and become visible. Nuclear envelope dissolves. Spindle fibers form.
• Metaphase: Chromosomes line up at the cell's equator (the metaphase plate).
• Anaphase: Sister chromatids separate and move to opposite poles.
• Telophase: Chromosomes decondense. Nuclear envelope reforms. Cell prepares to divide.
• Cytokinesis: Cytoplasm divides. Two daughter cells form. (Technically separate from mitosis but often grouped with it.)

Meiosis

Cell division for sex cells (gametes). Produces four genetically distinct haploid daughter cells from one diploid parent cell. Two divisions: meiosis I and meiosis II.

• Meiosis I: Homologous chromosomes pair up (synapsis), exchange genetic material (crossing over) — this is where genetic variation is introduced — then separate. Produces two haploid cells.
• Meiosis II: Like mitosis on the haploid cells. Sister chromatids separate. Produces four haploid cells total from the original parent cell.
• Result: Each gamete (sperm or egg) has half the chromosomes of the parent, genetically distinct from siblings.

Mitosis vs. Meiosis

Common TEAS question pattern: "Which of the following is true of meiosis but not mitosis?"

• Mitosis: 1 division, 2 identical diploid daughter cells, somatic cells, growth and repair.
• Meiosis: 2 divisions, 4 distinct haploid daughter cells, gametes only, sexual reproduction.

Topic 3: Genetics

Mendelian Inheritance

• Gene: Unit of heredity. Codes for a trait.
• Allele: Variant of a gene. (Brown eye allele, blue eye allele.)
• Genotype: Genetic makeup. (BB, Bb, bb)
• Phenotype: Observable trait. (Brown eyes, blue eyes)
• Homozygous: Two identical alleles (BB or bb).
• Heterozygous: Two different alleles (Bb).
• Dominant: Expressed when present (B in Bb shows as dominant phenotype).
• Recessive: Only expressed when homozygous (bb).

Punnett Squares

Set up Punnett squares to predict offspring ratios. For a cross of two heterozygous parents (Bb × Bb):

• 1 BB (homozygous dominant) : 2 Bb (heterozygous) : 1 bb (homozygous recessive)
• Phenotype ratio: 3 dominant : 1 recessive

For dihybrid crosses (two traits), the classic 9:3:3:1 ratio appears for two heterozygous parents (BbRr × BbRr).

DNA Structure and Protein Synthesis

• DNA structure: Double helix. Sugar-phosphate backbone. Nitrogenous bases pair (A-T, G-C). Antiparallel strands.
• Replication: Semiconservative. Each new DNA molecule has one old and one new strand.
• Transcription: DNA → mRNA. Occurs in the nucleus.
• Translation: mRNA → protein. Occurs at ribosomes. Codons (3 bases) specify amino acids.
• Genetic code: 64 codons, 20 amino acids. Multiple codons code for the same amino acid (degenerate code). Start codon: AUG (methionine). Stop codons: UAA, UAG, UGA.
• RNA vs. DNA: RNA has uracil (U) instead of thymine (T), is single-stranded, has ribose instead of deoxyribose.

Topic 4: Biological Macromolecules

The four major classes of biological molecules. Know what each is made of, what it does, and where you find it.

Carbohydrates

• Made of: Carbon, hydrogen, oxygen (C:H:O ratio of 1:2:1).
• Function: Quick energy source, structural support (cellulose in plants).
• Types: Monosaccharides (glucose, fructose), disaccharides (sucrose, lactose), polysaccharides (starch, glycogen, cellulose).

Lipids

• Made of: Carbon, hydrogen, oxygen — but with much less oxygen than carbohydrates.
• Function: Long-term energy storage, cell membranes (phospholipids), hormones (steroids), insulation.
• Types: Triglycerides (fats and oils), phospholipids (cell membranes), steroids (cholesterol, testosterone).
• Saturated vs. unsaturated: Saturated has no double bonds (solid at room temp, animal fats). Unsaturated has double bonds (liquid, plant oils).

Proteins

• Made of: Amino acids (20 types) joined by peptide bonds.
• Function: Enzymes, structural components, transport (hemoglobin), immune defense (antibodies), hormones (insulin), muscle contraction.
• Structure levels: Primary (amino acid sequence), secondary (alpha helix, beta sheet), tertiary (3D folding), quaternary (multiple subunits).
• Denaturation: Loss of structure due to heat, pH change, or chemicals. Often irreversible.

Nucleic Acids

• Made of: Nucleotides (sugar + phosphate + nitrogenous base).
• Function: Storage and transmission of genetic information.
• Types: DNA (deoxyribose, double-stranded, ATCG), RNA (ribose, single-stranded, AUCG).
• ATP: Adenosine triphosphate. Cellular energy currency. Technically a nucleotide.

The 2-Week TEAS Biology Study Plan

• Days 1-3: Cell structure and function. Make a chart of organelles with structure and function.
• Days 4-6: Cell division. Compare mitosis vs. meiosis side by side.
• Days 7-10: Genetics. Practice 30+ Punnett squares. Memorize DNA-RNA differences.
• Days 11-12: Macromolecules. Make a 4-row chart for the four classes.
• Days 13-14: Practice questions across all topics. Review weak areas.

Common TEAS Biology Mistakes

• Confusing mitosis and meiosis. The single most common biology error. Memorize the differences cold.
• Skipping Punnett square practice. The skill builds with repetition. Reading about Punnett squares does not translate into solving them under time pressure.
• Memorizing organelles without function. Knowing the name "Golgi apparatus" without knowing what it does is wasted effort. Always pair name with function.
• Confusing transcription and translation. Transcription is DNA→mRNA (in the nucleus). Translation is mRNA→protein (at ribosomes). Mnemonic: transcription is "writing" (DNA to RNA), translation is "interpreting" (RNA to protein).
• Overstudying biochemistry. The TEAS does not require detailed metabolic pathways like glycolysis or the Krebs cycle. Skip them.

Frequently Asked Questions