One of the most overlooked tools on the AP Biology exam is the formula sheet. Many students don’t realize how much it can help — or worse, assume it covers everything when it doesn’t.
In this guide, we’ll break down what’s included, what you need to memorize, and how to practice using it efficiently.
1. What’s on the AP Biology Formula Sheet
The College Board provides a short formula sheet in the exam booklet. Here’s what you can expect:
- Chi-Square Formula χ2=∑(O−E)2E\chi^2 = \sum \frac{(O - E)^2}{E} Where O = observed value, E = expected value.
- Water Potential Formula Ψ=Ψs+ΨpΨ = Ψ_s + Ψ_p Solute potential: Ψs=−iCRTΨ_s = -iCRT
- i = ionization constant
- C = molar concentration
- R = pressure constant (0.0831 L·bar/mol·K)
- T = temperature in Kelvin
- Hardy–Weinberg Equations p+q=1p + q = 1 p2+2pq+q2=1p^2 + 2pq + q^2 = 1
- Surface Area and Volume Formulas
For cubes, spheres, and cylinders (used in diffusion, cell transport questions). - Rate and Slope Equations
Rate = change in Y ÷ change in X (applies to enzyme activity, photosynthesis, etc.).
2. What’s NOT on the Formula Sheet
You’ll still need to memorize or understand:
- Metric prefixes and conversions (µm, mm, mL, etc.)
- How to interpret and rearrange formulas (e.g., solving Ψ for solute potential alone)
- Population growth models (logistic vs. exponential curves — formulas may not be given)
- Common constants (like R) beyond the pressure constant if used in context
- Units — the sheet doesn’t explain them, but AP graders expect correct units in answers
3. How to Use the Formula Sheet Effectively
- Practice with it early – Don’t wait until exam day to see it for the first time.
- Highlight relationships – For example, in Ψ = Ψs + Ψp, understand how changing pressure potential impacts total water potential.
- Use it as a check – Even if you memorize formulas, glance at the sheet to avoid small mistakes.
- Link formulas to concepts – Don’t just plug numbers in; explain the biology behind the math.
4. Common Formula Sheet Mistakes
- Confusing variables – Mixing up O and E in Chi-square leads to wrong results.
- Ignoring units – Missing units can cost points in FRQs.
- Not showing work – Even if the formula is given, you must write the setup and steps to earn full credit.
- Panicking over constants – Many constants are given or cancel out — know when precision matters.
5. FRQ Example Using the Formula Sheet
Question:
A plant cell has a solute potential of –3.0 bars and a pressure potential of 2.0 bars. Calculate the total water potential.
Answer:
Ψ=Ψs+ΨpΨ = Ψ_s + Ψ_pΨ=−3.0+2.0=−1.0 barsΨ = -3.0 + 2.0 = -1.0\ \text{bars}
Since water potential is negative, water will move into the cell only if the surrounding solution has a higher water potential.
RevisionDojo Pro Tip
Create a one-page "Formula + Practice" sheet with:
- The exact AP Bio formula sheet content
- A 1–2 sentence biology explanation for each formula
- One practice question per formula
By review week, you should be able to answer those practice problems in under 10 minutes.
Frequently Asked Questions
Q: Can I write on the formula sheet during the exam?
A: Yes — you can annotate and highlight it in your booklet.
Q: Are formulas on both MCQ and FRQ sections?
A: Yes — you’ll have access to them for the entire exam.
Q: Should I memorize them anyway?
A: Absolutely — familiarity speeds up problem-solving and reduces stress.
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