ATI TEAS Biology: Cells, Genetics, Macromolecules, and Microbes

Where Biology fits in ATI TEAS Science

ATI's Version 7 content outline gives Biology five objectives: cell structure, function, and organization; the relationship between genetic material and the structure of proteins; Mendel's laws of inheritance; the structure and function of basic macromolecules; and the role of microorganisms in disease. Genetics is one connected part of that list, so a Biology plan that turns into a Punnett-square chapter leaves most of the category untouched.

ATI assigns 9 scored items to Biology, out of 44 scored Science items. That number covers the whole category. ATI does not publish counts for each objective, and the 6 unscored Science pretest items are not identified, so no one can promise a fixed number of genetics, cell, or microorganism questions on your form.

As of October 2026, ATI's exam-details page still says TEAS Version 7 is live, and ATI has announced no successor. The same five objectives therefore apply if you test in 2027, unless ATI publishes a dated change. The ATI TEAS Science study guide shows how Biology sits beside A&P, Chemistry, and Scientific Reasoning.

Cells: tie each structure to a job

Cell questions get easier when every structure is attached to what it does:

• Cell membrane: a phospholipid bilayer that controls what enters and leaves the cell.
• Nucleus: holds the chromosomes in a eukaryotic cell. Mitochondria carry a small amount of their own DNA, so the nucleus holds most, not all, of the genetic material.
• Ribosomes: read messenger RNA and assemble proteins.
• Mitochondria: generate most of the cell's chemical energy, stored as ATP.
• Endoplasmic reticulum and Golgi apparatus: proteins made at the ER move to the Golgi, which processes and packages proteins and lipids, especially those leaving the cell.

Then ask three questions of any cell scenario:

1. What structure is involved?
2. What process does it support?
3. What would change if that process failed?

Here is an original example. A cell copies DNA into messenger RNA normally, but its ribosomes do not work. Stored DNA is not the problem. Protein assembly is, so every process that depends on new proteins can be affected too. When a label alone does not explain a result like this, practice cell structure-and-function questions with explanations in full ATI TEAS prep →.

Organization scales upward

The outline's word "organization" is a reason to connect levels:

organelle → cell → tissue → organ → organ system → organism

A tissue is a group of similar cells, an organ combines several tissue types for a special function, and a system combines organs. The stomach, for example, is built from muscle, connective, epithelial, and nervous tissue.

Prokaryotic and eukaryotic cells differ in organization. A eukaryotic cell has a nucleus and membrane-bound organelles. A prokaryotic cell, such as a bacterium, has neither, yet it still carries DNA and builds proteins: bacterial cells read the same genetic code as plant and animal cells. "No nucleus" does not mean "no DNA" or "no protein production."

Cell division links cells to inheritance. Body cells divide by mitosis, producing two cells identical to the parent cell, for growth, repair, and replacement. Meiosis produces eggs and sperm with half the usual chromosome number, 23 in humans, so fertilization restores 46. ATI's outline does not name either process, so study them as connections rather than as a prediction of how often they appear.

Follow genetic information from DNA to a trait

The most reusable Biology chain is:

gene (DNA) → messenger RNA → protein → cellular effect → trait

A gene is the basic unit of inheritance, and most genes code for proteins. In transcription, the cell makes a messenger RNA copy of a gene's DNA sequence. In humans, that mRNA moves from the nucleus to the cytoplasm. In translation, a ribosome reads the mRNA three bases (one codon) at a time and adds the matching amino acid, building a chain that folds into a protein.

Proteins do much of the cell's work. They act as enzymes, hormones, channels and carriers in the cell membrane, receptor sites, and structural materials. Shape matters because a protein's structure determines what it can bind or do.

An original cell-to-trait example

Suppose a plant gene codes for an enzyme in purple pigment production. A DNA change alters one codon, so the enzyme gets a different amino acid at one position. If the changed enzyme folds differently and works less efficiently, less pigment forms and the petals are paler.

Check each link in that chain:

• The DNA change does not become pigment directly.
• The changed sequence alters the protein's amino-acid sequence.
• The protein change matters only if it affects structure, amount, location, or function.
• The visible trait follows from the changed process.

Not every DNA change alters a trait: some changed amino acids leave the protein working. Many traits, such as height, are polygenic, influenced by two or more genes and often by the environment too. The chain is a reasoning tool, not a claim that every trait has one simple cause. To test the transcription and translation steps until they are automatic, review the DNA-to-protein steps with Science flashcards in full ATI TEAS prep →.

Mendelian reasoning tracks alleles into gametes

An allele is one version of a gene's DNA sequence. In the basic model, you inherit two alleles for a gene, one from each parent, and each egg or sperm carries one.

Use precise terms:

• Genotype: the allele combination, written with symbols such as BB, Bb, or bb.
• Phenotype: the observable trait, shaped by genotype and environment.
• Homozygous: two identical alleles.
• Heterozygous: two different alleles.
• Dominant: the allele expressed when the two alleles differ, masking the other.
• Recessive: the allele whose trait appears only when both copies are present.

Dominant and recessive describe an inheritance relationship. They do not mean an allele is better, stronger, or more common.

Work from gametes before probabilities

Take an original single-gene model in which P is dominant and p is recessive. One parent is Pp; the other is pp. The first parent can pass on P or p, and the second can pass on only p.

Half the boxes are Pp and half are pp, so each offspring has a 1-in-2 chance of showing the dominant trait. That chance applies to each offspring independently. A family of four could still have any mix, so a Punnett square predicts probabilities, not exact family outcomes.

For a two-gene problem, check whether the problem states or implies independent assortment. Genes close together on the same chromosome are more likely to be inherited together (linkage), and polygenic traits do not follow simple Mendelian ratios. If grid problems keep going wrong at the gamete step, revisit missed inheritance questions with Fix It in full ATI TEAS prep →.

Macromolecules link structure, fuel, and cellular work

The four groups have different building units and roles:

Classification is only the first layer. Connect each group to cells and to genetic information: phospholipids form the membrane, DNA stores information, RNA helps use it, and enzymes, almost always proteins, speed up specific reactions without being used up.

An original comparison shows the relationship. If a mutation changes the shape of an enzyme that breaks a large molecule into smaller units, the immediate problem is a change in protein function. The downstream effect may be on how the cell gets or processes nutrients.

Avoid assigning one purpose per group. Proteins are not just muscle material, and lipids are not just stored energy. Use the role described in the question.

Microorganisms in disease need cause-and-evidence thinking

Germs are microorganisms, visible only through a microscope. The main types are bacteria, viruses, fungi, and parasites, which range from one-celled protozoa to worms. Many microorganisms live in and on the body without causing harm, and some help keep us healthy. Disease involves a harmful interaction, not the mere presence of something microscopic.

Viruses are not cells. A virus is a segment of DNA or RNA inside a protein coat, and it cannot copy itself alone: it must infect a cell and use the host cell's components to replicate. Bacteria, by contrast, are single-celled organisms, and most of the bacteria in the body are harmless. Antibiotics work by killing bacteria or making it hard for them to grow, which is why they treat certain bacterial infections and do not work against colds or flu.

At exam-prep level, organize the topic around:

• the type of agent and its basic biological features.
• how it enters, uses, or affects a host.
• how damage or disrupted function can produce signs of disease.
• how transmission evidence differs from coincidence.
• how host defenses interact with the agent.

For an original investigation, suppose a researcher compares two matched culture plates. One receives a test substance and one does not, and fewer bacterial colonies grow on the treated plate. The result supports an association between the treatment and reduced growth under those laboratory conditions. It does not establish safety, effectiveness in a person, or a treatment recommendation.

This material is exam preparation. Do not use it to diagnose an illness or choose patient care.

Audit the full Biology scope

Before you call Biology review finished, answer each question without notes:

• Cells and organization: Can I connect an organelle to a process and to a larger level of organization?
• Genetic material and proteins: Can I trace information from DNA through RNA to protein function?
• Mendelian inheritance: Can I list possible gametes and explain a probability without turning it into certainty?
• Macromolecules: Can I match each group's building units with more than one role?
• Microorganisms in disease: Can I separate an agent, a mechanism, evidence of an effect, and an unsupported clinical leap?

The checklist stops a strong genetics unit from hiding an unreviewed macromolecule or microorganism objective. It also shows whether a miss came from missing knowledge or a broken connection between topics.

For body-system structure and regulation, use the ATI TEAS Anatomy & Physiology guide. For a quick mixed sample first, try the free ATI TEAS practice questions.

Draw one connected Biology map

Pick one cell structure, one gene-to-protein step, one inheritance model, one macromolecule, and one microorganism mechanism. Draw arrows showing where they connect, then explain which arrow would break if one fact changed.

That map tests relationships that transfer to new scenarios without any claim about live items. Then practice the whole Science section, Biology included, in full ATI TEAS prep → and tag each uncertain answer by the link that failed.