5 Common but Least Understood Terms in AAMC MCAT Passages
One of the biggest mistakes MCAT students make is getting stuck on scientific vocabulary instead of focusing on the experiment. The AAMC intentionally includes technical terms that may seem intimidating, but most simply describe straightforward scientific concepts. Learning to recognize these terms can make passages much easier to read and help you focus on what the question is actually asking.
Here are five of the most common but least understood terms you’ll encounter in MCAT research passages.
1. Sparsely
One of the most overlooked words in AAMC passages is sparsely. By itself, it simply means not very much, few, or widely spaced apart.
The word is often paired with another scientific term, so pay attention to what is being described.
For example:
Sparsely branched glycogen
This means the glycogen has fewer branches than normal.
Think of two trees:
- A tree with hundreds of branches is highly branched.
- A tree with only a few branches is sparsely branched.
On the MCAT, this distinction is important because glycogen that is sparsely branched contains fewer α(1→6) glycosidic bonds, longer straight chains, is less soluble, and is more likely to accumulate inside cells. This is exactly what occurs in Lafora disease, where abnormal glycogen becomes insoluble and damages neurons.
MCAT Tip: Whenever you see the word sparsely, mentally replace it with “less of something.”
2. Covalently Linked
nother phrase that appears repeatedly in MCAT passages is covalently linked.
A covalent bond forms when atoms share electrons, making it one of the strongest types of chemical bonds in biology.
If two molecules are covalently linked, they are chemically attached and generally require a chemical reaction to separate.
Common examples include:
- Amino acids joined by peptide bonds
- Sugars joined by glycosidic bonds
- DNA nucleotides joined by phosphodiester bonds
When the passage discusses proteins, the phrase covalently linked should immediately make you think of disulfide bonds. Disulfide bonds form between two cysteine residues and are one of the most common covalent bonds tested on the MCAT. They help stabilize a protein’s tertiary structure, and when they connect separate polypeptide chains, they also stabilize quaternary structure.
MCAT Tip: Whenever you read covalently linked, think “permanently attached.” If the passage is about proteins, always consider disulfide bonds.
3. Incubated
Many students hear the word incubated and immediately think about bacteria growing in an incubator.
In research passages, the meaning is much simpler.
Incubated simply means the researchers mixed the necessary components together and allowed the reaction to occur under controlled conditions.
For example:
Muscle extracts were incubated with UDP-glucose.
This simply means the enzyme, substrate, and other reagents were placed together for a period of time so the reaction could proceed.
Nothing more complicated than that.
MCAT Tip: Think of incubated as “mixed together and allowed to react.”
4. Autoradiography
At first glance, autoradiography looks like one of the most intimidating words in biology.
In reality, it’s a relatively simple laboratory technique.
Researchers label molecules using radioactive isotopes such as:
- Carbon-14
- Phosphorus-32
- Sulfur-35
As these isotopes undergo radioactive decay, the emitted radiation exposes photographic film or a detector.
The darker the band, the more radioactive material is present.
The MCAT commonly uses autoradiography to determine:
- whether a molecule was synthesized,
- where a protein traveled,
- whether DNA was replicated,
- or how much product was produced during an experiment.
MCAT Tip: Think of autoradiography as taking a picture of radioactive molecules.
5. Normalized (Normalized Data)
Research papers frequently state:
“The data were normalized.”
Many students assume this involves a complicated statistical calculation.
Usually, it doesn’t.
Normalization simply means researchers adjusted the data so different samples could be compared fairly.
Researchers may normalize for:
- protein concentration,
- sample size,
- radioactive decay rates,
- cell number,
- or loading volume.
Normalization doesn’t change the biological result—it simply removes unfair differences between experimental groups.
MCAT Tip: Whenever you read normalized, ask yourself:
“What difference are the researchers correcting for before making comparisons?”
Final MCAT Takeaway
The AAMC is not testing whether you know every scientific word in biology. It is testing whether you can quickly recognize unfamiliar terminology, understand it in context, and continue analyzing the experiment.
Mastering words like sparsely, covalently linked, incubated, autoradiography, and normalized will help you read passages faster, avoid getting distracted by jargon, and focus on what really matters: interpreting experimental data and answering the question.